Tuning a stripped Nikki?
 

So I figured since so many folks recommend removing the rat's nest and cleaning up the carb, I decided to find out for myself. I took out the rat's nest according to this nicely done tutorial:

http://maz_tutorials.ten15.net/Tutorial_1.pdf

I'm pretty sure I got everything hooked up right but I have pictures if there are any questions on that.

Then I rebuilt a stock Nikki and stripped it down according to:

https://www.rx7club.com/1st-gen-archive-71/intake-carb-rebuild-how-strip-nikki-down-648376/

Again I was pretty meticulous and I think I got everything right, but I have photos if that would help.

The problem is, while the car has more spunk and is kind of fun to drive, especially when you've got the rpms up above 3000, I am also having some problems:

1. I can't get a smooth idle below around 2000 rpms. Whenever I adjust it down to about 1500, it dies right away. Even if I tune it a little higher (around 2000) it will only idle for 10 or 20 seconds, then it dies out. It's kind of like having a serious vacuum leak, but I've checked and rechecked and can't fine a leak.

2. I'm getting quite a bit of back firing when I let off the gas pedel at speed. I know some folks like this "pop-pop" sound, but I'd just as soon have some peace and quiet and not draw attention.

3. The gas mileage has slipped quite a bit from what I was getting with the stock Nikki, down from 23-24 mpg to about 16 mpg.

So I'm wondering if I've got something wrong or if these "problems" are just normal when you remove all the emissions and carb "accessories".

Any help would be much appreciated, if I can't get it to run better it looks like I'll be reinstalling a stock Nikki and rat's nest this weekend.

Thanks
Ray

I don't know much about carbs yet Ray, but here is my idiot's version for you. :D Between the poor idle, and crappy fuel economy I'd say you are running very rich. Plus the backfiring makes me think this as well. I'm guessing that when you idle down there is so much fuel, the lack of air to mix with it kills the car. Your mixture sounds like it's so rich that its just fuel and practically no air. As far as finding out what is causing this, hopefully one of the carb brothers will show up and help out.

Rx7Carl?! Sterling!!!??? :D Where are you guys?

ray, my advise to you coming from another who DDs a nikki. go undo what you did about stripping down the carb. this seems ratehr odd for you to be doing anyways. we all know your reputation;) id install all the stuff you took of the carb. i dont really see why anyone who DDs their car would want to do that anyways. esspecially the mechanical secondarys.

keep the rats nest off. if im not mistaken you removed your AC recently, correct? i dont really remember what all you still have to have hooked up to the nipples below the carb. i suggest keeping the vacuum advance. i also suggest plugging it into the nipple fartheest to the left(closest to front of the car). i had mine on a different nipple and when i switched it here noticed good results.

mine backfires if i full throttle for a little bit then let off, but mine is due to exhaust leaks.

try this and see what you think. dont throw the rats nest back on just yet.

The high idle and backfiring are being caused by a large vacuum leak.

also whenb you let off the gas you can get the backfiring from A: running rich or B: a removed or malfunctioning shutter valve. are you still using your coasting valve or did you remove it?

He removed the rats nest, that means the shutter valve would be inoperative because it is controlled thru the emission system.

That's correct Doc, the shutter valve is blocked off and I'm sure this is contributing to the backfiring. Also I wonder if removing the anti afterburner valves might have something to do with it.

Also I removed the AC, PS, cruise control, hot start assist and vacuum secondaries (they are wired for mechanical), but I don't think these would be a factor.

I wish I could blame it on a vacuum leak, but I've been over the whole system several times and I'm sure I have every hole blocked, so I'm guessing that this is just what life is like with a stripped Nikki and the rat's removed.

The engine bay looks terrific right now, but all those emission controls and clutter are looking pretty good too, in retrospect. Looks like I might be putting them back it.

I would like to get a second opinion from Rx7Carl or Sterling, since they seem to have had better luck, or anyone else that's had good success with this approach.

But if I can't get it worked out by tomorrow morning, in goes the stock Nikki and rat's nest.

Anybody interested in a freshly rebuilt stripped down Nikki?

And thanks for the suggestions folks, keep them coming!

Ray

Here're some pictures of the situation:

http://memimage.cardomain.net/member...7_225_full.jpg

http://memimage.cardomain.net/member...7_226_full.jpg

http://memimage.cardomain.net/member...7_227_full.jpg

http://memimage.cardomain.net/member...7_228_full.jpg

.

I'll give it a try aws after I give that stripped Nikki one last go around today, if it doesn't improve out goes the stripped Nikki, in goes a stock one.

One nice thing about ripping out the rat's nest is I've learned more about what all that stuff does, so I can eliminate things I don't really need, if any. If I put the nest back in I'm going to paint all those manifold tubes black, that should look pretty cool.

hi ray i have done what u have several time's now and you should be able to idel at 800rpm no sweat and get at least 20mpg

when i stripped my nikki i alway's jb welded the alt compensator holes and the vaccum secondary holes also i have found if you use the gaskets provided by the rebuild kit for between the carb and spacer plate and between the spacer plate and manifold it allways seemed to cause leaks

are your float levels correct maybe this could affect it's running ability
are you positive you cleaned out the idel circuit with compressed air cause bits of shit will affect it to:)

just my 10cents mate
have a good one

"hi ray i have done what u have several time's now and you should be able to idel at 800rpm no sweat and get at least 20mpg"

This is what I was hoping to hear, now I know it is possible, thanks blwfly!

I JB welded the altitude compensator holes, you can see the job in this photo:

http://memimage.cardomain.net/member...7_227_full.jpg

I put rubber caps on the secondary holes, they are in this picture, right? I'm not sure exactly which ones they are without looking at the diagrams:

http://memimage.cardomain.net/member...7_226_full.jpg

Here's a close up that might be a little more clear:

http://memimage.cardomain.net/member...7_230_full.jpg

The float levels are correct, the fuel level in both view ports is halfway up the glass.

I used solvent and compressed air to clean out and blow out ALL circuits at least twice and checked each one individually for good air flow with the compressor, so I don't think there are any problems there.

Thanks, an idle at 800 rpm and 20+ mpg would do me just fine!

You've gotta love those diagrams. So are these the secondary holes that blwfly says needed to be sealed with JB weld?

http://memimage.cardomain.net/member...7_231_full.jpg

I was looking at these when I did the rebuild and thought they were just screws mounts for the secondary diaphragm assembly. Also I checked the holes when the car was running but detect any vacuum leaks.

But with a closer look I see the second hole down is a port. Does this need to be sealed and could that be causing some of the symptoms?

Thanks
Ray

Yep.

Thanks Jeff, I'm mixing the JB now.

Here's the secondary ports sealed:

http://memimage.cardomain.net/member...7_234_full.jpg

And I touched up the altitude compensator ports while I was at it:

http://memimage.cardomain.net/member...7_233_full.jpg

So I'll wait for this stuff to dry, hook it up tomorrow and see what happens.

In case it doesn't work, I also fixed up the rat's nest:

http://memimage.cardomain.net/member...7_235_full.jpg

Ray, you stil have the shutter/coasting valve in place. I remove them entirely, then tap the hole left by the shaft and JB Weld an allen plug or bolt in the hole. If you've removed the butterfly from the valve, you can get away with leaving it in.

I know you can get more than 20 mpg. I just got 20.5 coming back from the Iowa meet with the 1/2 bp and the DCDs. My mileage is down a bit, it it's very close to the correct tune.

hehe there usally is allways somthing ya missed:)

yeah and do what scott said cause that will have a major affect if the butterfly is still there itl be blocking the second rotors primary maybe why you cant get a low idel and your having to use you secondarys to keep the car goin

Thanks for maintaining this thread Ray. I'm sure that I'm going to be looking back at all of this in a couple of weeks when I start my Nikki rebuild. :D Please let us know how things turn out once you JB Welded those ports.

BTW: Did you follow those diagrams in the archive that I put together? The ones where everything is all red and green? I'm interested to know if this set of plans will actually work when building the carb. Please let me know if you followed the plans, with Rx7Carl's recommendations of course. :)

Well I've still got the problem, won't idle under 1500 rpm. Sealing the secondary ports and tying that shutter valve butterfly open didn't make much difference, unfortunately. I might have some timing issues, I'm looking into this.

Trochoid, I just wired the butterfly open with some stainless steel wire so it was in the vertical position, since I might need to be putting the rat's nest back in. I tried to unscrew and remove the butterfly, but those little phillip screws won't back off easily, probably because the engineers didn't want small screws and butterflies dropping into the intake manifold.

Mr. Ham, yes I used your annotated diagrams throughout the procedure, they were very helpful for identifying parts and issues. Then I crossed that with Carl and Dennis's de-ratting tutorial. Other than JB'ing the secondary ports, I think I had everything right the first time.

So I don't know what to think about the problem with the idle, could be the stripped Nikki or could be the guy that stripped the Nikki.

But it's an interesting problem, I think I'll kick it around another day or two before I put the rat's nest back on.

Again, thanks folks, especially Trochoid, for the info.

Ray

I hated the mech secondaries when I did them. Sure, the power was there, but I couldnt stand the hesitation and loss of gas alll the time. Plus, when I wired them and drove it, I parked later and looked at the car and saw some residue (gas?) on the side that wasnt there before.

jsut my 2 :)

So it turns out the timing is according to the book, pin straight up and the dizzy pointing to L1, the way I had it all along.

This will start the engine, but I can't get it to idle unless I advance the timing by setting the pin 5-10 degrees clockwise relative to the first notch. That's the best idle I can get and it still needs to be 1500 rpms or more to keep running, if I reduce the idle speed below that it dies out. Also, if I set the pin toward the first timing mark, it dies out.

It's this weird timing behavior that made me think the timing must not be right, but I've checked, rechecked and rechecked. Then read some FSM's and tutorials and rechecked again, and it looks like the timing was correct all along.

So it must be the stipped Nikki.

Other than the idle problem that the engine seems to run strong, screaming in fact. It revs like it's never revved before. But all for nothing if I can't sit in traffic and not cause a scene.

What about those cut off valves, the ones wired to large brass fittings that are sticking out on each side of the carb? These operate a pair of cut off pins and they have weird names and functions I don't fully understand.

Using the best info I could get from Carl's tutorial, I just unplugged this one:

http://memimage.cardomain.net/member...7_234_full.jpg

And I took the spring out of this one, then just reinstalled it (hard to see in the photo, but it's the one with the brass fitting in the upper center):

http://memimage.cardomain.net/member...7_226_full.jpg

And here is one more photo showing the plumbing more clearly. The vacuum advance is unhooked and blocked off because I was setting the timing. It's tube is lying right underneath the dizzy connections and it hooks into the second port at the base of the carb which you can see in the photo above:

http://memimage.cardomain.net/member...7_240_full.jpg

Could the cut off valves be cutting off an idle circuit or something and causing the idle problem? If anyone has any ideas or info on whether this could cause the idle problem I'd sure be grateful.

Stu, the jury is still out on the wired secondaries, I want to see what they are like once I get this tuning problem fixed. But it's a slippery slope, once you put the vacuum secondaries back in, then reactivate the choke, shutter valve, etc, you might as well use a stock Nikki and rat's nest.

A rotorhead visited yesterday for parts, had an exceptional 85 GSL with fresh paint that was meticulously maintained and virtually all stock, cats installed, all the power accessories and yes, it was an automatic. Beautiful car and it ran perfectly. The driver said it even had balls.

So anyway, I'll give this experiment a few more days, maybe I'll start randomly messing with those shut off valves and see if that helps.

Carl, where are you??!!

Ray

That is for your idle compensator. You should have 12 volt ignition running to it. If you are shure that you have everything hooked right, try this before you go back to the rast nest. Disconnect every vacuum line running to the carb base plate, including your vacuum lines going to the dizzy. Set the leading timing to 8* degrees advanced. This will move your trailing to 12* retarted, providing you had the trailing at 20 before you advance the leading. Your mechanical advance will still work.

I had a similar problem a while back but never really figured out what exactly went wrong (maybe a throttle/choke shaft seal)... Just for shits and giggles, try spraying a little carb cleaner around the back of the carb, around the float window and throttle/choke shafts and see if your rpms change if you haven't already sprayed there.

I forgat to add, if you want a FB intake with the shutter valve removed, block off plates installed, and cleaned to pristine condition, I can hook you up.

wow thats a pretty crappy problem mate you have seem to have coverd most of the area's

i have had the same symptoms before and that was a combo of not blocking the secondary's vaccum ports and a screw had stripped by the the fuel bowel which caused a major vaccum leak

also im currently rebuilding a stripped nikki for the 12a in my repu :)

Thanks Mr. Bad, I've already got the block off plate on this one but haven't removed the shutter valve because that's a one way trip for the intake manifold. But that gives me an idea, I do have two extra manifolds sitting out in the back yard. Maybe I'll do one of those up.

But like I said earlier and because of Trochoid's warnings about the shutter valve, I took a real close look at this and when I couldn't remove the shutter valve easily, I just wired it so it stays in the open position. Shouldn't that take care of the problem?

When you say disconnect every vacuum line leading to the base plate, does that include the plumbing for the crank case vent? I tried to follow the instructions on that but never fully understood what it was all about. So that's another good idea, I'll unhook it and plug the ports and see if it helps.

Thanks Mr. Bad.

"Just for shits and giggles, try spraying a little carb cleaner around the back of the carb, around the float window and throttle/choke shafts and see if your rpms change if you haven't already sprayed there."

Yup already sprayed there, no difference, but thanks for the suggestion.

Yes, everything. This is the only way to make sure that you do not have something plumbed wrong. With everything disconnected, then you can rule out any error on your work. Then you can try checking for leaks around yor carb and intake. The backfiring and not being able to idle is coming from a lean condition. Hense everyones diagnosis of a vacuum leak. I run a blowthrough Nikki on my FB without any problems. This mod your doing is a simple upgrade.

Got it, the sun's going down but I think I'll go hook up a lamp.

Ray

might help!
 

ok i have done tons of these you could pretty much plug all of them. i think your problem is that you have a vacumn line poen which i think is the one right where the vacumn line goes to the brake booster, sometime it hides because of the stock spacer in between the carb and the intake manifold. if you look closely at the top part of the exhast manifold and right where the intake manifold is at on your left when staanding over the carb. there is three tubes that come out of the intake manifold one has a bolt that holds it in place and another one goes to the exhuast(long pipe that comes in the side of the side of the exhuast flange) then there is a small tube thats about the size of a finger nail, take a good look. reason why i tell you is because i just did one about two weeks ago and had the same problem would idle high and i could not get it lower than 2000 rpm. and also back firing. take a good look. if you remove the spacer inbetween the carb(which is that long black plastic thing) i will try to take a pic on one that i have around here, good luck:icon_tup:

I hope this helps you find your problem. When you are ready to commit to mechanical secondaries, you will need to brase to linkages together to prevent any stretch on your wiring job. This will also insure the secondaries fully open at wide open throttle.

help 2!
 

the one that my finger is pointing to! Is this one plugged?check the pic

Thanks jm, if that's the one up on the air horn that the crankcase vent hooks up to, I thing I got it plugged (see the red cap). Also I removed all the vacuum lines from the base plate, capped the tubes and plugged in the shut off valves too there sockets.

And yeh Mr. Bad, I'll brace the secondaries if I like it, which means the friggin thing needs to idle.

Here're some photos of the current situation:

http://memimage.cardomain.net/member...7_241_full.jpg

http://memimage.cardomain.net/member...7_242_full.jpg

Still no change, the idle still sucks, but the good news it there is getting to be less and less to mess with.

I've also sprayed it down pretty good on several occaisions with starter fluid, looking for vacuum leaks, no results. That plus a lot of attention during the rebuild rules out vacuum leaks, I think.

Why won't this sucker run?

are you talking about the red cap by the fuel lines at the carb? because the pic is o fthe intake manifold below that black spacer plate!

I know you sprayed it down pretty good from the sound of it , but did you do around your ACV block off plate?
Also, I'm not sure right now, but I think the separate chambers under the block off plate can be a leak if they are not sealed from each other and the tube that bolts on toward the back of the manifold is not sealed.

Mr. Foxx,

So you mean this one?

http://memimage.cardomain.net/member...7_243_full.jpg

OK, so I plugged it:

http://memimage.cardomain.net/member...7_244_full.jpg

Here's a movie of the White One idling at 400 rpm, which I don't think she's done before:

http://youtube.com/watch?v=MhbD59XSlIg

Thank you Mr. Foxx, you know your rotaries.

Ray

you got it!!!!!!!!!!!
 

thats happen to me before. the spacer blocks the view,what i would normally do is crack the excess of the spacer which would allow me to view that pipe,but when i would leave it stock that would happen, but anyways good luck!!! glad i could help!!!!

How's she running now Ray? Pretty good? Just curious to see if this fixed your problem...

hay have you got a close up on how you tired youy mec secondarys im trying to find a better way than using wire

also you can get rid of two linkages ones for the cruise controll and the other's for subzero start..
https://www.rx7club.com/attachment.p...1&d=1181663226
https://www.rx7club.com/attachment.p...1&d=1181663226

Well let's start with the good news. I used stainless steel mirror hanging wire for the secondaries, they have held up without stretching for the entire week that I have been working on the car:

http://memimage.cardomain.net/member...7_245_full.jpg

Now the bad news, when I put this cap on that port coming out of the intake manifold:

http://memimage.cardomain.net/member...7_244_full.jpg

the car will idle smoothly all the way down to 300-400 rpms and it revs quickly and smoothly when sitting in the driveway. But when you go out on the street, it runs like crap, really really bad. At first I thought something had happened to the ignition but everything looked good there.

So I removed the plugs, which turned out to be fouled black, obviously a very rich mixture with that cap on the manifold port, great for idle but no power.

So I took the cap back off and I was back to where I started, rough idle that's hard to keep going in the driveway, but get it out on the street and it runs like a rocket, including some nice explosive backfires here and there. Much better, at least, than with the cap on.

That capped port on the intake manifold connects to a tube that runs to the #2 anti afterburner valve, which was removed during the stripping. Makes me wonder what is going on with the intake that isn't right.

I don't think the problem is with a leaking block off plate, I used silicone gasket sealer to make a seal by coating the plate before I put it on. But could the gasket sealer be causing some kind of problem in those ports it covers up if it gets down in them? I'm redoing the plate, but just putting the sealer on the contact points at the sealing surface of the intake manifold, but frankly, it's just more grasping at straws.

More clues, but the problem is still the same. Why is it running so rich that it needs an additional air intake to run OK? (float levels have the gas halfway up the carb windows, so I don't think it's flooding).

So I'm about ready to put the stock Nikki back on and go from there unless somebody has another suggestion.

Thanks
Ray

Don't give up Ray! You've already found a couple of oversights here and there, so you're bound to find the one that's causing the problem pretty soon. This might be a dumb suggestion, but you did adjust your mixture screw after putting the carb back on, right?

ok so did you readjust mixture screw if so go 2 to 2and a half turns so you could rule that out, second and the pic with the carb you have a long hose going towards the distributor are you using that? third the vacumn lines from the distributor you could have them open, so un plug them, forth that shutter valve thats in the intake manifold did you mess with that if so make sure the shutter valve stays open since you have the vacumn closed it might be closing on you! let me know,one thing that i always happen is it will run perfect,but when drive the car around and let it sit it will take a few seconds to turn on, but never had the problem you are saying.

Thanks Mr. Foxx and Mr. Ham, you guys have as much patience as I do.

1. Yes I did readjust the mixture screw after every change that I made by turning it out three turns, then back in until the engine slowed a bit, then back out half a turn. This always turned out to be around 2-3 turns from all the way in.

2. I have the hoses set up according to Carl's tutorial, here's the pictures showing how they are attached:

http://memimage.cardomain.net/member...7_225_full.jpg

http://memimage.cardomain.net/member...7_226_full.jpg

3. When testing for vacuum leaks I did have the vacuum lines from the distributor plugged both at the distributor lead tube, with a bolt, and at the carb plate (hole #2 from the left in the spacer plate) with a rubber cap.

4. I did take a close look at the shutter valve when it was disabled and the flap pretty much wanted to stay in open on its own, but just to be sure I wired the shaft so it had to stay open.

So I'm plumb out of ideas. Last night I decided to switch in my stock Nikki, which has everything on it except the #2 anti afterburner valve, leaving the rest of the set up exactly as I had it for the stripped Nikki (in other words, according to Carl's tutorial).

Wow. The car runs great, better than ever, I'm happy and back to normal. But building that stripped Nikki was fun and educational, the engine bay is cleaner than ever and the car is fast. I hope the photos and discussion were of some use to those considering this mod. It might be a good one, but I would suggest having someone with experience with stripped Nikki's nearby when you do it.

Also thanks to Doc and aws, who suggested early on that they didn't think this was a good idea. With a little more experience, I now tend to agree with them!

Now, what to do with that stripped Nikki?

swap the nipple your vac advance is on. put it on the nipple farthest to the front/left.

Yeh aws you said that before, but why would it make a difference?

I've got the stock carb back in and the car is running great, blazing in fact. I'm having to get used to driving it all over again. But there is still a high idle, I can't get it below 1000, which really isn't that bad, just annoying.

So if I swap that tube it'll idle down? I'll go out and see.

OK I went out and swapped the vacuum advance tube to the front port and capped the second. But there's no difference at all in the idle or driveway revs. Runs great, just idles a bit high.

Anyway, anybody interested in doing some experiments on that stripped Nikki? I'd like to see somebody make it run right.

Ray,

I might be willing to do some experimentation with it. I was going to strip down my Nikki per the specs of the thread that I put together with all of the diagrams. However, if I had your carb already stripped then I could troubleshoot it and hopefully get it running right.

After that is done I can use my stock carburetor to do a complete writeup with actual pictures on stripping down the Nikki. I think the experience from tuning a stripped Nikki would make my own adventure much easier. It would also be a nice addition to the archives.

Jamie

Just another thought Ray, did you ever check the tension on your throttle cable? There is a chance that you had it too tight, which would obviously keep the car from being able to idle down properly since it would always be at partial throttle. I know that I myself have made this very same oversight on a couple of different occasions...

I think you'd be a good one for the experiment, I'm confident this thing would run great if it were hooked up right. I was very careful with the rebuild and it's my second Nikki, along with several other carbs over the years. And my first Nikki rebuild (that one stock a few months ago) is in the car and running fine, although I still haven't figured how to get the idle down to 750 (it's currently at 100 rpms, which is OK). I'll pm you with what it would be worth for me to put it in a box and send it out.

And yes the throttle cable has enought slack at idle, that's not the problem with my slightly high idle, although I'm thinking I might not have somethinq quite right with the throttle linkage and adjustments, so I'll be looking at that this evening.

Ray

The idle problem turned out to be this do-dad. Loosen the phillip screw, move it out a bit and then go back and forth between the carb idle and this gadjet. I'm getting a smooth 750 rpms on the stock Nikki and the throttle is very responsive. I'll have to go look it up in the FSM and see what it does, might have helped the stripped Nikki, I don't know.

http://memimage.cardomain.net/member...7_246_full.jpg