I intended to just continue the bike work over on GRM, but I can never get photos to upload correctly. So I'm going to continue to post them here and people not interested can skip those posts.

I wanted to finish the rotisserie stand, but after a trip to the hospital overnight Saturday for what I thought was my appendix, the doctor has diagnosed my pain as "something muscular" and told me to rest until it's better. Which means no lifting of heavy parts. I still think it's something else - I don't remember pulling anything on Friday. But either way I'm on light-duty until I'm better.

The bike continued to have no spark. I diagnosed one issue as a broken wire in the harness between the stator / points connector and the coil itself, but bypassing the wire didn't help. Then I thought it was the coil itself, but the spares that came with the bike are slightly different and aren't a direct fit.

I had already cleaned the points without any improvement. I bought a battery before realizing that the battery actually has nothing to do with the ignition on this bike. It's very very basic - one of the stator coils is dedicated to generating the power for the ignition coil. When you kick-start the engine, the action of spinning the engine is what generates the charge. In fact, 2/3 of the stator coils aren't even for ignition. They're just for the charging system.

So then I measured the stator coils and found the resistance higher than spec. Trouble is that these stators are long since NLA and the used market is thin. I decided the first thing to do was to take out the coils and determine if any of the solder joints had been corroded by the elements to cause the increase in resistance. If not, then the next step would be to inspect and determine how feasible it would be to rewind them. That was more difficult than expected since someone has been in here before and rounded all of the JIS fasteners:



I spent awhile trying to free the outermost three and remove the assembly in one piece, but it wasn't going to happen. I also couldn't safely use a torch here. I was ready to build some sort of shield for the coils and weld a nut on top of the screws, but my dad had a much better idea to simply remove the coils from the bracket:



This still required a chisel to break one of the bolts loose. However, on the whole it was a lot less dangerous than welding near the coils.

We were also pleasantly surprised to see that the wire for the breaker point fell right off. Normally this wouldn't be cause for celebration - but this obvious problem means that the coils might actually be alright.

Then with the coils out it only took about two minutes to remove the stuck screws:





This does mean I'll need to replace them, but they aren't hard to find.

The coils don't look bad, although there is some discoloration on the enamel:





This one isn't discolored - just dirty



This one's also dirty. You can see the insulators I was talking about that are broken off. If I end up rewinding these coils I'll definitely replace them with something, but otherwise I don't think they're really necessary.



Reconnected the wire to the points:



If I decide to keep this bike long term, I'm definitely going to need to replace all the wires. I'll probably go for sealed connectors at the same time - why not, there are only like 6 of them.

Weirdly, every multimeter I have is telling me different readings for the coil resistance. Sometimes they don't even read the same back-to-back. Now most of my multimeters are as clapped out as the bike at this point, but the only one that gave me a consistent reading is this one:



And somehow, it was right in spec. So I think the game plan is to clean the coils, coat anyplace where copper is exposed (if I find any), and then reinstall with new fasteners and see what happens. If it still doesn't spark, then I need to dig deeper.

 

so this one time, i had a really minty 1979 Rx7, and i had rebuilt the points distributor, mostly for the challenge. i hadn't messed with points since school
me and Node hopped in it, and drove down to LA for Sevenstock and on the way back i stopped at the gym, and when i came out it wouldn't start.
towed it home, and the wire for the points had broken. the tricky part was that the INSULATION for the wire was fine!

i'm enjoying the bike, btw.

 

Today I spent some time working on the spark issue. Sorry about the poor photos - I was in a bit of a rush and ended up using my phone rather than my actual camera.

When we left off, I said I was going to bolt the stator coils back on and see if fixing that wire to the breaker point resolved the issue. In short - it didn't. I reconnected it and nothing happened.

I then started suspecting the ignition coil. I checked and found that the body of the coil had zero continuity to ground. The coil body grounds to it's bracket, which grounds to the chassis. I sanded some of the scale off the back of the bracket and off of the chassis, and there was no improvement. Then I noticed something:



That's not right. An 11mm nut? There's no way this was factory. So then I took it apart:



And there was actual dirt between. Of course there was no continuity. There's also no way this coil is OEM, because:



It doesn't fit properly on the bracket. The coil certainly looks period-correct, but I don't think it's for this bike. The two mount holes are also too far apart for the bracket. Lastly, it was not installed with a bolt, but instead a small splined stud:



So it goes without saying that someone had been in here. But even after bolting the coil straight to the body I had no spark. I used the 6V battery I bought to power the coil directly, and wouldn't you know it, it started sparking as intended. While the ground was a problem, it certainly wasn't the only problem.

Next (no photos for this part, but it's all parts you've seen) I took the stator back apart and looked at it for awhile with my dad. I noticed a couple of things:

- The wire I repaired for the breaker point was too short, so it was pulled awkwardly and the tab was grounding out on the body.
- I think the tab was also on the wrong side of it's insulator, which would still result in being grounded out against the body. Not 100% sure since I took it apart before checking.
- The breaker point was maladjusted. I don't recall the spec off-hand, but the gap was way too big.

Once all these things were fixed, we had spark! So the cause of the issue was lack of attention to detail on my part, and hackery on the previous owner's part. I used some electrical tape to splice the plug wire (a new coil is on it's way already) and I then wanted to see if I could get the bike to fire.

I took the carb off and sprayed carburetor cleaner directly into the intake, and then kicked the engine over a bit. No dice. Then I tried starter fluid, same result. I tried cleaning the plug a few times and also verified again and again that it was sparking, but I just couldn't get it to fire. I didn't expect much, but I would at least have expected a single pop.

I even tried a direct injection (pun intentional) of fuel into the spark plug hole:



But there was no change.

I noticed one thing that could cause this, which is that there is a LOT of blowby coming out of this port on the crankcase. To the point that I put some electrical tape around this port and kicked the engine over a few times, and I could hear the air whistling past the tape for about 10 seconds when I stopped.



I suspect this means that the rings are seized and aren't sealing properly. No surprise, given that there had been some water in the cylinder. I put MMO in there last time and the compression was around 120psi after cycling it awhile. I would expect 120 to at least run, if not well. This time I filled the cylinder with Seafoam (for variety), all the way up to the brim. Neither MMO nor Seafoam will dissolve rust though, so at the end of the day I might just have to replace the rings before this bike will run.

I'm going to continue trying over the next few days, but now that I have spark my biggest concern is alleviated. It looks like I can get OEM replacement rings for $50 and the top end gaskets for another $50, so I could potentially have it running for about $100. Much better than hunting down a replacement stator for $500 or a full 12V CDI conversion for $700.

Meanwhile this engine seems to be compatible with XR100 parts, and an XR100 120CC bore kit is about $300. Which I'm not eager to spend on a bike I have yet to ride, but it includes a larger piston with rings, camshaft, rocker arms, all the gaskets, etc. So $100 for OEM rings and gaskets puts me 1/3 of the way there.

Hopefully the rings free up and I get to ride it a bit before putting any more money in, but either way, I've made progress today and I'm feeling satisfied with myself.

 

I spent some time taking inventory of what parts I have, and then inspecting the bike:



Two aftermarket ignition coils, OEM carb, breather hose, spare spark plug, intake elbow, new throttle cable, assorted springs and fasteners.



Also a spare carb and the wiring harness. There was a ton of duct-tape on the end of the speedo drive cable, which I pulled off to find the cable is damaged:



As is the other end, which remains in the front hub:



So that will be another thing on the list to replace. Then the rear wheel adjuster is also looking pretty bent:



And I'd been noticing a weird clicking noise when I wheel the bike around, which I've determined is due to the extreme wear on the rear sprocket:



None of that is really a big deal, since all of those parts can be found on Amazon for very little. I also put the stator cover back on for now, since it seems to be working reliably.



The missing piece at the back tells me that the chain has broken at least once in the past. Long term I'll probably want to replace the cover - if a chain is going to snap, I'd rather it hits the cover than my leg. The side pegs are also welded for some reason. Not a huge deal although it would be nice to fix that eventually.

I took off the bad rectifier just so the connector wasn't flopping around, and this is the bracket:



I'm not sure if this is a non original piece, or if this is the original piece installed in the wrong place.



I checked through the spark plug hole and found that the Seafoam in the cylinder had leaked down quite a bit (although not all the way). I also managed to shoot Seafoam out of the spark plug hole, right onto my eye - fortunately my eye was shut and I don't think any got in there, but I still had a fun 15 minutes flushing it.

Gauged purely based on how much pressure I feel with my thumb against the breather, I think the amount of crankcase pressure when I kick the engine over has decreased. Perhaps the Seafoam has successfully freed up the rings a bit. It definitely softened some carbon that was in the cylinder. Still no luck getting the engine to fire, so I filled the cylinder (MMO this time) and left it for awhile longer:



I'm sure heat would break the rings loose, but then the only way to do that without disassembly is getting the engine to fire. Which is a bit of a catch 22.

 

Today I hit two milestones. One, I registered the bike. I was a little bit worried about this since I didn't have a title (previous owner bought it disassembled and sold me exactly what he had, which didn't include the title). That might have been okay except that since I bought it at a garage sale in less than 5 minutes, I didn't even have a bill of sale. I went back to the house (at least I think it was the right house) on Sunday, but nobody was home.

Anyways, I searched on the Government of Canada website to verify that the bike wasn't reported stolen (it wasn't). The previous owner struck me as honest, but just in case. Then I figured I might as well drive to the MTO and just ask them what I actually need to register it.

It turns out the answer is basically nothing. For bikes older than 1984 for off-road use, I just needed to sign a piece of paper indicating that I was the legal owner and pay the tax / fees. So only about 5 minutes and $16 later, I now have a title. Even though this made my life easier, I feel like they should demand a bit more.

I'm lucky enough to have helpful and informative staff at my local MTO, so she also told me that I could register it for the road but there are additional requirements. She said they have to make a call every time because the requirements change constantly (not sure how that works), but last time they needed a piece of paper from a dealership indicating that the bike was actually real and had the correct VIN, as well as an affadavit of some sort. It sounds like a bit of a headache, but nothing too crazy. For now I just registered it for off-road use so it's in my name.

The second milestone?

Well, I spent $10 on Amazon to get a new petcock since the original was leaking horribly. Original on the bottom, in case you couldn't tell:



They're mostly identical except for the angle of the outlet:



The included filter with the new petcock also doesn't fit, but that's no problem since I was also able to get 10 filters for $10:



Now, I still wasn't able to get the bike to start. I spent a long time kicking with no results. I don't know why I didn't think of this earlier, but there's a BIG hill next to my house...

So I decided to bump start it. To recap, I had:

- No rear brakes
- No clutch (not just no cable, but the clutch lever also doesn't disengage the plates)
- No kill switch of any sort, one wire from the stator to the ignition coil
- Never driven a dirtbike or motorcycle before. I've been on my brother's motorcycle one time, never actually driven. I know how to drive manual so the principles are the same, but then there's no clutch so I guess it's moot
- A huge pond that would swallow my bike should I not steer quick enough

I found that it wouldn't spin the engine when I dropped it into first, but on my next attempt down the hill I tried second and it burst to life. Then I drove around the backyard for a bit before driving back up the hill, sliding around the driveway a bit and then stalling it out using the brakes.

Now my dad was kind enough to stand by with the fire extinguisher and the video camera, but unfortunately he wasn't actually recording on my successful attempt. You'll have to settle for this video in my driveway:


I did attempt to recreate it for you, and technically succeeded, but I sacrificed a bit of skin in the process:







Fortunately I fell on the grass! But hey, it was only my second time ever riding a bike.

I made a few observations, first among them that this bike is NOT slow. I know that it'll run out of steam before it hits 90 km/h, but at low speeds it will absolutely try to do a wheelie when you snap the throttle open. This despite 44 years of neglect. The second observation is that there's quite a bit of smoke when I'm hard on the throttle. A lot of this is MMO burning off (and there's a good amount of MMO in the crankcase too at this point) but I'm sure some is also oil slipping past the rings and the valve stems. Thirdly, the bike actually runs really smoothly. Much smoother than I expected from a single cylinder.

There is quite a bit of blowby, but the oil is also a bit overfilled from everything in the cylinder draining down:



I think most of that crud is not from the inside of the engine. Some is from the crusty intake boot I stretched back onto the carb, and some of it is seat foam.

For safety purposes, I did make a kill switch for my second ride:



Rip the purple wire and the coil is disconnected. Still crude, but lets me kill the engine as needed. I can also just pull the spark plug wire off as it's quite loose, but that takes my right hand further from the handlebars so I thought this was a prudent choice. When I have some time I'll repair the harness so I can use the real switches.

So there we are! It runs, it drives (sort of, only in one gear since I can't shift) and it stops (with great care to not flip the bike). It idles. It makes decent power. I can wind it out in first and it works perfectly. I can snap the throttle open (with care, on a straightaway with good grip) and the engine happily responds. And now that I've freed up the rings, even when cold it starts on the first kick. I should check to see if the clutch works now since it might just have been seized.

It certainly isn't perfect, but the engine was my main criteria for whether this project was a go or a no go. Now it's a go.

My Rx7 will still take priority again as soon as my abdomen is better (awaiting an ultrasound). I really don't want it languishing in the garage too long. But in the meantime I'm going to spend a bit of time getting this bike safely drivable. It sat neglected for years in the previous owner's backyard, and now it's running in 8 days. I don't want to toot my own horn too much, but I'm quite proud of that.



Until next time

 

I decided to check compression on the bike again, since I'd now broken the rings loose:



Still low, but not terminal. About 140 vs a spec of 160. The bike still starts on one kick and makes good power, so I'm not really worried about that.

More worrying is that the cylinder head is probably on it's way out:



There were sparkles in the oil when I first changed it, and there are sparkles in the second fill too. To be fair though, part of this is user error. This is 5W20 I grabbed because I had it around, which is much too thin, and there's a fair amount of MMO / Seafoam in it that leaked down from the cylinder. It probably had a total of 10 minutes of runtime on this oil, but clearly this has been a problem for awhile.

The latest fill is 5W50 synthetic and so far I'm not noticing any sparkles on the dipstick, but either way the cylinder head is not long for this world. As an aside, I used 5W50 synth because it's easier to find and cheaper near me than 20W50 organic. We truly do live in strange times.

I purchased a new air filter sock. It felt a bit tight stretching it on there so maybe it's for a different bike, but it fit eventually:



I also took the box apart to clean it out. There's this weird filter thing for the crankcase breather:







I'm not sure why it was full of grass, but I cleaned it all out and installed it with a new hose:



I meant to put the stock rubber inlet hose back on, but it wouldn't fit. I realize that the end broke off of the original and someone stuck a piece of rubber hose from something else onto it, but the new hose section is too short and too stiff to fit. For now I bought a cheap air filter just so the engine isn't inhaling any dirt or debris:



I also bought one of these things for the spark plug:



Yes, I had been riding around without one until now.

To be continued

 

With that completed, I started turning my attention to some of the more glaring safety hazards. First is the rear sprocket, which needed to be replaced a LONG time ago. I started by loosening the main bolt and backing out the adjuster nuts:



Particularly confusing is that they didn't actually need 6 of these 7 washers. Why? Why would someone do this?



The other side is more of the same. The split pin was missing, which is always a great idea. Risk your safety for want of a $0.10 pin.

On this side the adjuster was just ruined:



They do have an inner and an outer side, so I'm pretty certain someone put this one in the wrong way and then just tightened it until it bent.

The brake also has some funky custom linkage. The factory piece is supposed to be round with a threaded hole, and it engages in that round hole on the pivot arm. Someone instead decided to drill out a speed nut and use a variety of nuts and washers to adjust it?



Again, why? The OEM part is $10. I've added it to my list for when I put in an order from CMS.

With that the bolt and spacers came out:









There was a TON of grease in there. Which is weird, because the bearings are the sealed type and wouldn't benefit from having tons of grease slapped on them. Obviously there should be some grease so that everything rotates smoothly, so on reassembly I used some of the red bearing grease.

The bearings look original and somehow feel perfectly fine, so I left them for now. If they're cheap I might replace them just in case. I had been wondering how the sprocket connects to the hub, now I can see that it uses these rubber bushing things:



Mine seemed a little loose, but nothing crazy. I will replace these as well when I make a parts order but they are certainly acceptable for the moment.

On the original sprocket two of the four steel blocks that engage into those rubber bushings were loose and wobbling around, so it was long past due for replacement:



Then there was this little cup and spacer thing:



I feel like there's something missing under the cup, because even though the bushing takes up the space properly there seems to be nothing preventing the cup from sliding around on the bushing. Meanwhile there's that very intentional looking channel in the spacer which currently has nothing engaging in it. Maybe a missing clip?

To be continued

 

Turning to the brakes for a moment, I wanted to see what was going on with the shoes. The pedal very much felt like there was nothing at all behind it.

Turns out that there are shoes in the rear, albeit quite worn:





Probably a little under 1/2 of the material left. I can see no reason these shouldn't work, so I think it's an adjustment issue (not surprising given the state of the linkage on the rear). There's a small rotating cam thing that pushes the shoes against the inside of the hub:



I gave it a healthy coating of silicone brake grease:



With that done I popped the brake assembly back onto the wheel and went back to working on the chain drive. The inner sprocket was also worn:



I found this piece of rubber from something behind the sprocket:



Not quite sure what it is. The drive sprocket is significantly better than the wheel sprocket, but still has visible wear on the teeth if you look closely:



The output shaft looks pretty ugly, but most of that is just old grease:



To be continued

 

The original chain is pretty bad:



There are multiple dings and kinks. I have a sneaking suspicion that this is the chain that snapped and damaged the stator cover. I'm assuming it snapped at the master link and the previous owner merely replaced the master link rather than the entire chain.

I installed my new chain and sprocket set:



This set is from Niche industries. I'd read some mixed reviews, but a lot of people seem to be running these chains without any problems. My brother has been running them on his XS400 and XJ600 for several years now without issue.

Tensioning the chain was a new experience for me. For some reason I felt like it should be fairly tight, but the manual sense 20mm of deflection at the center point of the bottom of the chain when pulled upward:





I guess that feels okay? Again, I've never owned a bike before.

For the rear brake I added one of the mysterious return springs that came with the bike:



Is that the right place for it? Not sure. For now it definitely feels right since the pedal actually comes back up. I also assume there's supposed to be some sort of rubber stopper here:



One more little thing on the list.

On the rear I installed the new adjusters, with only one washer:



And by pre-loading the pivot arm for the rear brake, I was able to actually make it functional:



While it has a long throw and doesn't feel amazing, the rear brake is now functional.

To be continued

 

I also had to turn my attention to spark again. A couple of days ago I rode it around the backyard for about 5 minutes before it suddenly stalled. I kind of thought the engine had popped, but the compression test showed otherwise. Turns out there was no spark. I adjusted the points again (properly this time, rather than by eyeball) and it ran again for about 10 seconds before losing spark once more.

The coil continues to work fine when 6V is applied directly, so I decided to investigate the stator again. I pulled it all back out (which is nerve wracking due to how rare this part is) and looked it over again:



Two of the coils have ring terminals on them, and if I gently pull the terminals away we can see that there's quite a bit of rust and grime in there. Leaving the stator covers off for years in the elements will do that. I spent some time cleaning away and sanding the little posts clean. I did this for every coil, as well as the bracket they bolt to:



I also measured some resistance across the screw terminal of the point, so I took it apart entirely:



Even after sanding it down, the point doesn't look great:



I'll probably buy a replacement breaker point too if they're available. After that I reassembled the stator on the bike, but I felt some slight grinding when rotating the rotor so I pulled it back off. I realized there was scale on the outside of the metal coil cores that interact with the magnets. The clearance here is important so I didn't want to take off any material, but I did gently sand away some scale and then wipe them clean:



I did the same thing for the rotor magnets:



I also found that there is some play in the bolt holes for the coils. For anyone else in a similar situation, loosen all 6 of the bolts that hold the coils to the bracket and then push the coil inward before tightening down again. Otherwise the rotor magnets can hit the pickups.

This fixed the scraping noise and the rotor turns smoothly now. It also seems to have (fingers crossed) fixed the spark issue. I'll keep an eye on it, but for now I think it's okay.

The clutch remains stuck. I rode it around for a few minutes with the clutch arm zip-tied inwards. This was in the hope that when dropping it into first and taking off, it would shock the clutch plates loose:



No luck, but I was able to ride around for a few minutes in the backyard and the bike is performing well. There is almost no smoke now on full-throttle, so I think the thick oil has helped a lot with the valve stem seals. It also seems to improving as I run it more, so it's possible there's still MMO burning off maybe? Not entirely sure. As long as it's getting better rather than worse, I am not complaining.



I do still need to reinstall the OEM harness and connect up the kill-switch for safety purposes before I ride it any longer. At present the only ways I can stop it are stalling it out with the brakes (if it's in gear this is my only choice) or pulling off the spark-plug wire. I can't seem to reliably get it into neutral (it always wants to go into second), but I think this is user error. It feels like if I click up gently it goes to neutral, but too much force makes it go to second. There might be some sort of adjustment in the shifter too, but I haven't looked into that yet.

Until next time

 

This morning the weather was nice, so I put on a helmet and went to the back of our property to try out all of the gears. I actually only made it to fourth, but still it was a lot of fun. I could go faster but I'd rather wait until I have better brakes and functional shocks before doing so.



Then I turned my attention to the aluminum shavings in the oil again. I popped the valve cover and inspected the cylinder head, and I was surprised to see that everything looked fine. I could put a screwdriver against the cam gear bolts and lever up and down, and there was almost zero detectable movement. Given the sheer amount of aluminum I'm finding in the oil I'd expect a lot worse.

I adjusted the valve clearance while I was in there and then I went to adjust the timing chain tensioner:



Another weird non-OEM bolt. It does the job though. There was no noise before, and after adjusting there is still no noise. I figured that wasn't the cause of the aluminum but it was worth a look anyways. I drained the oil and found there is a LOT of aluminum in there:



Given that this is now the third drain of the engine that's had aluminum in the oil, I think there would be some detectable slack at the cam by now if the journals were wearing out. I also hadn't freed the clutch yet so I thought I would pop that cover and see what was going on.

This required removal of the brake and kick-start levers for clearance:





Then the cover itself:



I also ended up removing the carburetor and exhaust. They don't really need to be removed, but I had to weld out most of the fasteners since they were seized. This meant I had to remove the exhaust for clearance and the carburetor for safety.

Here's the clutch:



Nothing visibly wrong under here, except all the aluminum shavings. Nothing wrong on the cover either:



But then I found something weird. There's a lot of side-to-side slack in the kick-starter shaft. I tried (without much success) to photograph it:





And if I leave the kick-starter shaft in it's resting position and turn this gear:



I feel a distinct scraping or grinding. Meanwhile if I push the kick-starter shaft in the opposite direction and turn the gear, I feel nothing.

I think this issue is going to require splitting the case to diagnose further, but that puts me at a bit of a crossroads. I clearly can't keep riding around like this or else I'll incur additional damage - but splitting the case means removing the piston, bore, and head. That means there's never a better time to install a big-bore kit or any other upgrades I want.

If anyone has any idea what might be causing this issue, I'd appreciate their input. I have to determine what's damaged and find out if replacements are available before I do anything else.

At least I managed to free up the clutch while I was in here

 

A user over on GRM correctly pointed out that the kick-start shaft is supported by the clutch cover. So the play in the shaft is probably due to the cover being off. He also helpfully suggested I clean out the filter screen (these bikes don't have a real oil filter):



Not much to clean out! Not sure if I should be worried about the fact that the oil was unfiltered, or thankful that the screen didn't get clogged with aluminum shavings and block the oil supply.

 

I found where the aluminum is coming from, and it's definitely from the timing set. Looking at it closely there's definite wear marks on the outside of the chain links:





Possibly on the rivets too, although it's hard to tell sometimes whether it's friction marks or just marks from when the rivets got peened over.

My first clue was that the chain doesn't ride centered in the guide. Look at how far out it sits from the center:



It's actually visible in the way the chain sits as well. Observe the sprocket teeth on the left of the photo which are towards the outside of the chain, then on the right they're now towards the top. The chain isn't riding straight.



Now for the smoking gun, look at the other side of the chain:



It's also sitting way out towards the outside of the case rather than centered in the guide, and we can see that it's wearing something away (I think part of the bore):



That is the source of my aluminum shavings. The really weird thing is that I didn't hear any unusual noises. I would have expected a rattling or a slapping or something. Maybe there is a noise and I'm just not detecting it.

Anyways, it was very fortunate that the oil screen was ripped away since I am 100% certain the aluminum would've clogged the screen and there would have been no oil flow. They're available pretty cheaply on CMS and I'll need to put in an order anyways for some other parts.

Replacing the timing set means removing the head, and since it's already down on compression a big-bore kit makes a lot of sense. This bike isn't slow or anything but a 20% bump in displacement is nothing to complain about. Also I'm pretty sure that the casting the chain is grinding through is part of the bore (although whether it's an important one, I'm not sure). At the very least, I don't need to buy a new cylinder head.

My plans are not 100% certain (I'll have to do some shopping) but I think I'll remove the engine from the bike for access since it's only about 6 bolts. Then with the stator cover and clutch cover removed and the bore / head off to the side, wash out all of the aluminum that I can access. I'd like to avoid splitting the case if possible. Take apart the head to replace the valve stem seals and wash all of the aluminum out of that too. Then it's new bore / cylinder and associated gaskets, high flow oil pump (I hear mixed reviews on their usefulness, but it can't hurt) and reassemble. After that it's frequent oil changes and cleaning the screen every change until there is no more aluminum

 

I spent a few minutes doing some further inspection on the bike today. Starting with the cylinder head journals which are of course known for wearing out. I know many bike engines don't use replaceable bearings, but man, I really wish they would.

Luckily mine don't look so bad:



There are some marks, but it's smooth and doesn't catch a fingernail. Comparing it to the other side which looks pretty much perfect:



It's clear that the timing sprocket side gets more wear. Not enough for me to replace the head though. I think with heavy weight oil, regular changes, and a high flow oil pump this head should still have a lot of life left in it.

The cam caps and rockers look excellent:



As does the camshaft:



Those marks on it are just contact marks, and aren't actually wear. They're all perfectly smooth.

You know what isn't perfectly smooth though? The timing chain guide:



Those grooves aren't supposed to be there. Clearly this has either been over-tightened (not sure how that happens with an automatic adjuster) or possibly the plastic decomposes with age and the chain starts to grind it down. I don't think oil changes are the culprit since the rest of the engine doesn't show any of the typical wear from poor lubrication.

There is a second adjustment for the guide using the top bolt, which is eccentric:



So before using the bottom screw for the automatic adjuster, it looks like you can also adjust this to increase or decrease the tension. Maybe the previous owner over tightened it? They clearly went and messed around with the tensioner before since they managed to lose the stock adjustment screw. Oh well, either way the path forward is the same.

On closer inspection I think the casting being ground away by the chain isn't part of the bore, but part of the case itself:



That worried me a bit at first, but I think that casting's only job is to locate the other plastic chain guide. So it isn't actually under any kind of load. It's a good thing I found this now though since I might need to replace the case if the casting was totally ground away.

I also propped the cylinder head up to get a good look at the bore:



Pretty much what I expected for an engine that had water sitting in it. Although honestly, I am surprised it managed to make like 140 PSI of compression given how bad it looks. I think there also might have been a tiny leak into the crankcase, but it's hard to tell since I don't have access to look at it straight on. That would explain my crankcase pressurization issue though.

Exhaust valve is dirty but looks okay:



Ditto for the intake valve:



I couldn't seem to get the bore to separate from the case and I didn't want to hammer it too hard with the dead-blow or it might damage the fins:



For now I just put it back together with everything finger-tight. Since the bore is pretty bad (as expected) and the big bore kit is a cheap solution, I'm going to grab the TB120 kit. It has everything I need and is reasonably priced. Otherwise I'm not doing any modifications outside of the oil pump for reliability.

Hopefully parts should start arriving soon and I can start riding it around for real. Until next time

 

i think the timing chains stretch a little, and when they are loose they start slapping things around.
also the plastic guides work ok, but they do wear.

i used to sit across from the warranty guy, and our customers have trouble with timing chains, and um well its like a bomb went off in there usually.

 

It's interesting. Everything used to have a timing belt, and people don't like those for obvious reasons. It's another thing that needs checking and replacing, and if / when it does snap you're going to have a bad time (on interference engines, anyways). But when belts were common, they were at least predictable.

Then manufacturers moved to chains and now it tends to either work really well or really poorly. We've had several cars with chains that hit 300 - 400k km with no signs of any issues, and then there are BMWs and Subarus that seem to eat the guides and apparently some Fords stretch the chains.

 

the Audi/VW 4 cylinders are a problem too, and some of those 2.0 engines have a timing belt also, which is inexplicable, lol
the Ford V6 is fun too, they did kind of a stealth update, where there isn't a recall or bulletin, but there is an upgrade from a 1 row chain to two
that Ford engine also has another problem, there is a water pump right where you expect it, and that is fine, but there is another one (?!) behind the timing cover. so when it fails it dumps coolant in the oil.
if you decide, you want to be proactive, and change it early, its behind the timing cover, so engine needs to come out of the car for like 20 hours.

i don't really know much about Subaru, except that the parts books we had floating around the office have the part numbers for the engine on the cover!

 

Apparently my abdominal ultrasound shows "nothing abnormal" despite the fact that it continues to hurt randomly. I have however discovered that lifting things doesn't seem to aggravate it, so that means I can start on the Rx7 again soon.

Anyways, I have the big-bore kit in hand as well as the timing set. I'm missing a few small parts from CMS but I was at least able to get started. Taking the engine out only took about an hour, working at a leisurely pace:



From there I popped the cam and caps off, and worked the timing chain off of the camshaft sprocket. For one horrible moment I thought I'd have to split the case to remove the chain, but if you're careful it slips out of the opening for the crankshaft:



Then I popped off the head and the bore and set them aside. The piston looks good:



But here you can see just how much of the case has been eaten away by the chain:





That's a lot metal, but fortunately this casting doesn't see any load. It just retains the left side timing chain guide. Speaking of which, the right side guide is well and truly dead:



The pictures don't capture this, but comparing it to my new guides, it's a lot less bowed out than the new one. I think the guide itself has not only been ground down, but also deformed itself over the years.

The bore would probably be saveable with a hone and possibly an oversized piston and rings, although it certainly looks bad:



If you look really closely, I think you can almost tell where the piston sat stationary for years in the previous owner's backyard with water in the cylinder. Maybe I'm just imagining it though...

The valves look fine, albeit quite dirty:



The timing chain slapping around actually managed to wear away a good amount of the timing chain region (whatever you call this area) in the bore as well:



And was starting to make it's mark on the head:



No wonder there was so much aluminum in the oil. I'm fortunate that the mesh filter was torn or else I would probably have lost oil pressure.

All of the removable parts and fasteners got a bath in the ultrasonic cleaner:





It did a really great job of cleaning any oil off of the parts, and that helped remove a lot of trapped aluminum dust.

 

I spent awhile spraying the cylinder head down with carb cleaner. It's going to need a proper disassembly once I have new valve stem seals in hand, but until then it's nicer to handle when it isn't covered in oil and aluminum dust:



I like using an egg-carton for this, since it catches all of the debris and allows airflow under the part when you leave it to dry:



Then I wrapped up the head carefully and put it away for now. I'm going to have to try and find a good way to clean the oil passages out when I take it all the way apart. It's too big for my ultrasonic bath, so maybe I'll soak it in mineral spirits and just snake all of the passages with round brushes until it's as clean as possible.

Here's a side profile of the old tensioner:



Like I said, photos don't really capture how it seems to have flattened out. The new one is more curved on the left side. I think someone was also under the impression that tightening the hell out of the tensioner lock bolt would increase the tension:



I think to my eye the old chain (upper) looks slightly longer than the new, but it's hard to tell. The tensioner was clearly the main culprit.



And then I packed everything aside. CMS has yet to ship the remaining parts so I'll probably be waiting until at least next week to proceed, but that gives me time to clean the aluminum out of the case and cut some new gaskets.

Until next time

 

I've finished the welding for the second rotisserie stand for my Rx7, but I didn't take any pictures since it's identical to the work already done.

My order from CMS is supposed to arrive soon, and other than some gasket material that will be all I need to reassemble the bike. The Plastigage also arrived, so I set about checking the camshaft oil clearnace. Now the Clymer manual only lists the clearnace specs for 1998+ models and I've had a hard time finding if there was even a spec for the earlier bikes. Clearly they manufactured these to some tolerance at the factory but I can't find a clear published number anywhere. So I'll be using the 1998 spec as guidance:



I'm surprised to see that the wear limit is 0.20 mm, which seems huge. Even the maximum spec at 0.113 mm seems a bit excessive, but then this is an old bike and was made in the time of thick oils being the default.

The range on the Plastigage implies I should use the red one, unless I was measuring brand new parts and expect it to be tighter than 0.051mm:



With red Plastigage I'm getting 0.003" on the front journal near the timing chain:



And the same on the rear (the ruler is misaligned in this photo, but if I had three hands and got it aligned with the camera straight on you would see it is in fact 0.003"):



I only photographed the larger remnants because some stuck to the camshaft in the front and the journal in the rear, and vice-versa. But I repeated this test twice and got similar results, as well as observing the thickness across the journal to ensure that it wasn't wearing more at say the front edge of the journal than the rear. I think the rear might be slightly tighter than 0.003", but it's close enough that I'm not 100% certain. That would be consistent with the fact that I can see some small scratches on the front journal but nothing on the rear.

0.003" is 0.0762mm, which puts it comfortably within spec (assuming the spec is accurate). So I think we're good to go with this cylinder head. And frankly, even if I weren't, I'd probably still run this cylinder head for at least awhile rather than shelling out $300 for a new one or similar money to machine this one for bearings. But for the cost of a little Plastigage it's good to know the conditions of the journals.

Hopefully the parts arrive soon (FedEx tells me Friday). I'm also working on rearranging everything in our multiple sheds to make space for the parts yet to come off of the Rx7, so I have a lot to keep me busy until then.

 

My good sir, how's your body handling your recovery?

 

I'll let you know when I start recovering!

I feel exactly the same as I did when the pain first appeared. It comes and goes every couple of days for no reason that I can discern. It feels like something digestive, but I can't pin down anything I'm doing differently to cause it. The hospital thought it was muscular but that would have healed by now. An ultrasound shows nothing unusual, and I've had some sort of nerve pain on the other side of my abdomen / groin for a couple of years now which has also been imaged several times with no results.

I have an MRI appointment for the prior pain and I'm trying to get my doctor to redo the requisition to get the entire abdomen imaged so it also covers the new pain on my right, but it will be four months until my appointment as-is so once she redoes the requisition I still have to call around to try and find something sooner.

Apologies for going off on a bit of a rant, but it's frustrating. If I have one more doctor tell me I'm in "perfect health" I'm going to lose it. But at the end of the day it's more than tolerable and there are many people with ailments worse than mine, so I shouldn't be complaining

 

My order from CMS arrived with the last parts I needed (including valve-stem seals) so I proceeded with the cylinder head disassembly. I initially tried to do it without the valve spring compressor tool, but I pretty quickly realized it was mandatory.

Keep in mind as you read this that I've never done this before. I try to make all my posts informative so they can be used as an instructional guide later, but if it looks like I'm doing something wrong, I probably am.

I clamped the tool on:



Compressed the valve spring down far enough to remove the little retainers:



Removed the outer valve spring and the topper piece:



Then the inner spring:



And that exposes the valve-stem seal:



The valve pops out from the bottom, and that's all the pieces removed:



Now that was the exhaust side and I next did the intake side, which was identical except that there is no valve-stem seal:



A bit weird. I looked in the Clymer manual and it says that there is no valve-stem seal used on the intake side of "85 up XR100R heads". So either the entire engine has been replaced or the head has been replaced. Based on what I've observed from the previous owner, probably the latter.

After a lot of cleaning the intake valve looks reasonably good:



The exhaust valve is a lot darker:



I think the exhaust valve might have been the one left open when the engine sat for years with no spark plug. It's normal for them to get sooty but that's just my hunch based on the valve and the seat in the cylinder head

 

Around this time I also took apart the clutch fork (or whatever it's called, it's not really fork shaped) from the clutch cover so that I could clean and paint it:







I am normally not a fan of painted aluminum, but these covers were painted from the factory. So I sprayed them both with a silver engine enamel paint, and let them bake for the day in the hot sun (while also giving the cleaned cylinder head a chance to dry thoroughly):







Not bad, if I may say so myself.

I cleaned as much carbon as I could reasonably remove from the cylinder head, although I didn't go crazy getting everything out of the exhaust side. I'm sure more could be done, but most of what you see here is discoloration and casting marks anyways.

I thought about a few ways to possibly increase power. Porting the intake runners, maybe smoothing the transition towards the valve. I also thought about polishing the inside of the bowl and the valve faces, just to help mitigate carbon buildup. But once I really took a look at the design of this head, I can see why anyone trying to squeeze big performance out of these engines replaces it. The valves are small, which wouldn't be terrible except that they're also at a really steep angle relative to the ports. So the air has to make a very awkward looking turn to actually get into the engine.

I settled for lapping the valves, but other than that I left the cylinder head alone:



Intake:



Exhaust:



Then everything got cleaned again before reassembly. I had two valve-stem seals, but since I only need the one I guess I'll have a spare:



And I also replaced the upper valve seats (at least I think that's what these are called):



The existing ones might have been fine, but they were fairly cheap so I ordered them as a precaution from CMS. Then reassembly of the cylinder head was the reverse of removal:

 

With that done I started on the reassembly of the engine proper. First I put the new timing chain in:



I think it could be put in after the bore and head are installed and then carefully fished upward with a pick, but it's less of a headache to put it in now and then pull it up as I go.

The new piston and rings look like good quality parts:



Not that I really know what I'm looking at - I'm used to engines with 3 moving parts. But all of the machine work looked good, and the piston rings weren't difficult to install. There are zero instructions included in the TB120 kit, so I followed the instructions in BBR's Youtube video. First I put on the brass coloured oil scraper ring. Then the two other oil rings went in the same ridge as the scraper, one above and one below. The black ring goes into the second from the top ridge, and the black ring with silver edge is the topmost. The text on both compression rings faces up.

Then I aligned the notches in the rings apart from one another for improved sealing. I'm not really sure I buy this - clearly compression is less if the ridges are aligned, but don't these turn around on their own as the engine runs? Seems like it wouldn't really matter if you put them in wrong as they won't necessarily be aligned forever anyways.

The video also had some helpful advice to get the piston into the bore before installing the wrist pin. This is a lot easier (and probably safer) than installing the wrist-pin and then trying to drop the bore on top of the piston and then getting the rings to compress.



There's also a big "IN" printed on the piston to tell you which side faces the intake:



Among the OEM parts I purchased was a new spring for the chain tensioner:





Which then installs like so. The long end of the spring goes up into the bore and hooks onto a little detent, and the bar on the bottom engages into a hole so it can slide up and down:



Then I worked the whole assembly down onto the engine case and installed the wrist pin:



Now one thing I noticed (only after fiddling around to get the bore and piston installed) is that of the six dowels on the engine, the two of them that were on the bottom of the original bore have a small hole in them. Presumably this is something to do with the oiling system, although I'm not sure exactly what:



So I did have to remove the bore and piston to swap the correct dowels in before reassembly. But hey, at least I noticed before I torqued down the head!

The new timing chain sprocket for the cam looks identical (as it should):



Other than the damage on the original:



I installed that onto the cam. I was a bit paranoid about the bolts backing out, so I added some blue Loctite for insurance.