Repuguy

Yeah vacuum leak is the only thing I can figure, thanks Qingdao, you're probably right.

I'm using a gasket I got from Atkins, with Permatex copper sprayed on both sides. It's decently thick and not worn out at all. I'd suspect the carb to intake spacer before I'd suspect that gasket. Speaking of which, I'm only running the factory spacer, no gaskets. I wonder if a light coating of copper gasket sealer would help there?

Car will rev, but then dies, even if feathered. I see 0 fuel through the primary boosters, even at 2k. I can easily see fuel in the secondaries at the same rpm if I crack them open.

Only other thing I can figure is a clogged 'Off idle port' in the primaries, but I checked all the passages, and they seem fine.

I suppose the same Mikuni carb that has our style air jets, also has the fuel ones? I'm seriously thinking of getting 120's in the primaries, like Jeff20b's.

Repuguy

Aha! Much thanks Qingdao, I had an epiphany after reading your post. The only part of the manifold I hadn't checked was the brake booster banjo setup. It was leaking oil/gas, so obviously air! I removed it and put some silver tape over it and amazingly the car now revs! So happy!

What's the correct method of sealing the banjo bolt to the manifold? I had a copper crush washer between the bolt head and the air-block, but this obviously leaked...

GSLSEforme

Needs two crush washers,think crush washers on brake line at caliper. Same thing. One crush washer between bolt head and fitting,other washer between fitting and manifold.

Jeff20B

iTrader: (13)

Copper crush washers can be heated with a torch and reused.

Your drilling of your jets was wrong. You don't need 120 jets if your primary venturis are stock. Stay at 92.

Repuguy

You're going to laugh, but I saw a bunch of blue smoke this afternoon when I went to start the car. I almost cried (what else can go wrong!?!) and then it went away. It was just remnants of oil pooling in the manifold, sigh.

OK, I think we're making progress here! Back to 92's on the primary fuel jets. My primaries and secondary venturies are cut, but I can't recall how much offhand. I used a copper crush washer, pounded it onto the bolt (gently) and a Nylon one on the other side so now it's sealed real good. The 7 now starts pretty dang easily, (11.7-12.5:1 at idle) and runs smooth up to 2k or 2500- then it hits a wall and goes lean. Like really lean. I can overcome the stumble with some footwork with the AP. I've tried moving the AP lever around by compressing and loosening the spring but that's not really helped. I'd think if it were a vacuum problem it would not idle/start at all. It's not likely a transition passage problem either from what I can tell of the carb manual. Kinda stuck.

Edit: Just replaced all vacuum nipples on the carb with brand new ones, found one or 2 that might have been cracked. It's an improvement, but still stumbles at around 2500, but less now. I'm going out tomorrow to put a bolt in the manifold where the Altitude thing bolts in. Just eliminating problems one by one.

Repuguy

Quick Update:

New Aluminum washer and cap for the abandoned Altitude Adjustment thing on the manifold. Still stumbles and goes lean around 2k..ugh wtf eh?

Getting a new dizzy here tomorrow, the mechanical advance is coming all in at low RPM, I think the springs are shot, and when I hook up the vacuum, the timing goes WAY off, like 40 degrees or so.

I think the problem is still in the transition circuit, just need to find it.

Repuguy

Finally found the vacuum leak! It was the dang omp lines! I didn't even think they'd leak air, at least not in any significance. But they've got tight clamps on the copper nipples leading into the carb now. So the carb has a snall stumble around 2k still, but it's much better. I also have a little stumble at tip-in when going into first, at less that 2k or so. Is that normal for a large street port? I'm still lean at cruise and under power (15:1 or higher), but the car actually moves itself now, it's awesome.

Interestingly, if I crack the secondaries (By adjusting their resting position), about .5mm to 1mm it solves all stumble problems. Beyond that it sounds like a bridge-port, and idles like it too!

Repuguy

New dizzy showed up! Checked both vacuum pots, and they're good, yay. Of course not so good was this part:


Those gear teeth are damaged!
Solution was to take the used gear off the old dizzy and put it on the new shaft:

Up top:


Car even starts up, I'm amazed...Will fine tune it tomorrow, but it's odd that the Leading ignitor is trying to occupy the same space as my alternator bracket...wtf eh?

Oh and I now have 2 new J109's if someone needs em. DLIDFI makes them irrelevant to me.

Jeff20B

iTrader: (13)

Is the bracket 180 degrees off? Maybe someone switched it around for some reason.

Repuguy

Yeah you're right, bracket is 180 off...it's upside down. I didn't notice because I had to pull if off the old dizzy and stick it on the new one. Dumb, but easy fix.

Jeff20B

iTrader: (13)

Sometimes people will do that to try to correct for a dizzy and OMP drive gear that was installed backwards on the e-shaft.

Repuguy

Huh, that would make sense. But mine was just 180 off, no problem, now fixed. Now if I could get rid of the lean stumble that would be awesome.

Jeff20B

iTrader: (13)

It's hard to diagnose carb problems over the internet.

Repuguy

Success! I've been an idiot! I should have listened to what my AFR gauge was telling me this whole time...I was too lean!

I put in my ghetto 120 main jets for my primaries and now the car runs great! No stumbles, no bogs, plenty of power, up to 4k. I haven't taken it any further, as the seals are still new. AFR's around 11.5 at idle, to 12.8 under throttle. Good numbers, if a little rich, but hey much better than before.

Oh and seriously, thanks Jeff20b, would not have made it this far without you and many other members help!

Just ordered a proper set of 110, and 120 mm jets of Amazon.

What are you guys doing for secondary fuel jets, in terms of manufacture/source? I'd think if I had to step up my mains 30% I'd likely have to do that or more for the secondaries.

Jeff20B

iTrader: (13)

Reduce the secondary air bleeds and you won't need to "step up" your fuel jets at all. The factory lets way too much air into the carb through the air bleeds so they needed to have large jets to cover an otherwise lean condition as the vacuum secondaries would open. Vac secs are kinda dumb though if you are wanting greater performance. If that sounds a bit cryptic, it's really more a matter of how much performance you want. The Nikki is the best carb for the rotary and can be modded to suit. It's just a somewhat difficult carb to get into due to a steep learning curve, as you are experiencing now.

Um, can you tell me more about these jets from Amazon? Are they jets or air bleeds?

Qingdao

iTrader: (3)

Have you drilled and taped your air bleeds? That helps a ton when fine tuning.

Repuguy

I'm getting my jets and bleeds from Niche Cycle Supply. They're a bit more expensive, but I get free shipping so it evens out.
The 120's I found: Mikuni N100.604 Large Round Main Jets N100.604 Genuine Genuine Mikuni Main Jets

Reducing the air bleeds makes sense. Kinda like what I did with the primaries. It's amazing to me that the Rotary worked at all with so much air bleeds, my AFR ratios were scary!

I'm definitely sticking with the Nikki as I'm very happy with it so far, now that I've decided to listen to what my gauges were telling me.

New tires, Federal 595 SS's ($47 on Amazon!) on their way! I know they're not the best tires in the world, but performance 13's (hell 13's that aren't built for a Prius) are hard to find.

Oh yeah, worked on the brakes yesterday too. I've had a rear caliper not settign right, since I installed it (didn't notice at the time). The E-brake wasn't holding either. When I got the wheel off, I could see that the caliper and pads were not centered on the rotor!

So 2 10mm washers later I had something like this

Now the rotor spins easily and my e-brake works! This car is almost roadworthy now!

Oh and one last thing I did, but forgot to take pictures of, is the new OMP lines. I bought 10' of Sioux Chief 1/4 o/d 7/64 id Chainsaw fuel line, at Home Depot, only $5. It's rated for oil and gas, is clear-orange and with a little heat, slides over the OMP and carb nipples fine. It has stopped the annoying oil leak I had using 1/8th inch fuel line.

chuyler1

iTrader: (1)

What's the I.D. of the factory line? I may have to try that out on my intake. I removed the OMP and started premixing but I hate it. So annoying. It's hard enough getting the gas not to spill when fueling my REPU.

Jeff20B

iTrader: (13)

The ID of factory OMP lines is tiny or rather capillary in size for a reason. It keeps oil in the lines while the engine is off. Otherwise the oil flows back down into the engine and you end up with dry starts if the ID is too large.

chuyler1

iTrader: (1)

That's what I thought, is there a way to get OE thickness lines? I've seen a few photos sprawled across this site, but no part numbers

Repuguy

New shoes for the 7! Federal 595 SS 185 60 13. I wanted to keep the stock rims, and tire size, for now. I know the Federals aren't great, nut for $46 ea, and a decent selection I think they can't be beat. THe only other thing Tire rack had in 13's were Nankangs, and some other unknown China brand, well besides $200 ea Hoosiers...


I'm going back tot he emissions testing station tomorrow, and hopefully it passes this time. I have the stock timing set now, and at idle sitting in the mid 12's and same under throttle. I don't smell many fumes so the O2 pump seems to be doing its job. Only other thing I can think of is to drain tank and fill with 5 gallons e-85.

Qingdao

iTrader: (3)

I kinda want to try those tires.. but I LOVE my RE71R's.

NO do not put E-85 in your car. You'll have to tune it again. E-85 requires 30% more fuel. I doddled with it for a time. If you are turbo charged it might be cool (extra boost pressure yada yada yada), but NA its not worth the time to re-tune for E-85.

Toruki

Cool. Make sure to pass on how they work out for you in the 185 60 13 sizing, inquiring minds want to know!

Repuguy

Yeah I was thinking the e-85 would be a bad idea. Maybe some other time.

I will update on the tires when I have some actual road time. I'd say they're loud, if I could hear them over the motor.

I did emissions testing again today, failed on CO, but passed on HC and NOx. Paassed by a giant margin on NOx (cold combustion chamber/rich environment right?), and just barely 3.47 vs limit 3.5, on HC. My CO was around 85, vs limit of 45.

I've since swapped in proper 110 Mikuni jets, and now the car is quite a bit learner, stays in the 13's under power and 14's at idle. It's definitely less power than my hand made jets, but it's cleaner and crisper throttle. I think I have a chance to pass emissions now! I'm going back tomorrow.

Any good advise for timing? When I disconnect the vacuum advance, and hook up a timing light, I'm sitting around 10 degrees advance with just mechanical at 1k rpm idle. Retarding would lower emissions right? I know it's bad for power but emissions is a different topic eh?

Colorado is an odd state, in that even to get a collector plate, you have to pass emissions first. Not only that, but all vehicles, all the way back to 1942 have emissions testing! There's no 25 year rolling deadline like most other states (even California if I recall!). I still find it hilarious, my old 71 F250 with horrendous emissions, you could smell it for a few minutes after it left, passed emissions testing easily...In fact most of our air pollution is particulate, which is environmental, not automotive. Not to mention that fracking/oil drilling emits more pollution than all of the vehicles on the road in the state.

Repuguy

I PASSED EMISSIONS!

The 110 jets worked great, here's the numbers: HC 2.45 / Limit 3.5 CO 12.26 / Limit 45 NOx .38 / Limit 5.

It's surprisingly clean really. And still makes decent power. I can feel there's more power beyond 4k, but I don't want to push it that hard yet.

Found out my idle mixture screw was 'self adjusting' and I'm going to try a new spring on it to make it stay put. It literally dies at the emissions station, and I had to help them start the car by turning it 1/8th richer lmao. Thankfully the tester's first car was an 83 FB so she was sympathetic!


I looked at my state's emissions laws, and 82 interestingly is a cutoff year for switching from PPM measurements to GPM, which is as far as I can tell much more strict. I would have passed the 81 limits with my old poorly tuned Weber, if that gives any clues. Are there any huge differences in emissions equipment on 7's between 81 and 82?

Also of note is the fact that this engine has a pretty large street port and exhaust ported, with headers! I'm running the O2 pump full time, with no ACV or any rats nest whatsoever. The PCV isn't even hoked up but they didn't notice! Just goes to show the Rotary can pass emissions with a good cat and a some carb tuning. I wonder what Mazda was doing with all of that junk on the car back in the day?