Insane rx-7

iTrader: (1)

Hey guys,

I am running a modified Nikki on my 12A. Its got mechanical secondaries and I don't know what jets its running.

Ok heres my problem. I can get the car to idle perfectly at 750. But when I depress the accelerator pedal the car runs like it has no power. Yet I can tune it so that it has tons of power but won't idle lower then 2,000 rpm's and the Idle speed screw bottoms out. I am not sure if i am doing something wrong with the linkage but it everything I try it doesn't seem to run right unless its idling super high.

Here is what I tried to do while tuning it. There is a screw beside the linkage to move the butterfly's open and closed. If i close them right off it idles perfectly once adjusting the speed and mix levels. But has no power. There is a spring loaded bolt that pulls the accelerator pump arm into the diaphragm to depress it and squirt fuel into the motor. I assumed that this was my issue. But after adjusting this both ways many times, my outcome became. Guess what! I can get it to run awesome but it idles high or I can get it to idle but run crap.

The other thing I tried was to open the butterflies just a little bit and the car runs better but had that high idle.

I believe I missing something with my tuning theory. I might not completely understand how the mechanical secondaries work on this carb. Tomorrow I am going to get some pictures of it so you can better understand whats going down. I think it might help if I had a good point to start from like. I know you turn the idle speed and mixture out three turns, but are the butterflies suppose to be open just a bit or totally closed off at idle? Is the acc pump suppose to start squirting instantly? I couldn't see any reason why it wouldn't.

I have run out of ideas on what is happening. I might just be missing something or just totally wrong with what I am doing. If you guys can offer any assistance I would be great full.

PS. I have searched and searched and can't seem to find anything that helps me out perfectly. I might just be using search wrong though. I haven't ever really been good at it.

Kentetsu

It may well be a carb issue that you have, but before going any further in that direction I would suggest you check out the following items just to be sure:

Cap and rotor
Condition of spark plugs and wires
Verify spark on both leading/trailing
And most important, check the timing

Any of those could cause the car to run without power at lower rpms. And many a poor soul has spent months chasing a carb issue only to find out that it was an ignition issue all along (and vice versa).

On to the carb-
I don't really understand this part of your post:

"There is a screw beside the linkage to move the butterfly's open and closed."

I can't think of what that might be. And yes, the accelerator pump should squirt fuel as soon as the linkage begins to move.

Look down into the carb while it is idling, and move the throttle linkage by hand so you can see how the fuel is flowing into the primary (smaller) barrels. Is it a good healthy spray, or more of a dribble?

If you want a better understanding of how the mech secondaries work, look in the FAQ section and you will find instructions on how to do the mod, along with an explanation of how it works and how it should be adjusted etc. There are also some writeups in the FAQ section on how to troubleshoot a carb issue that Sterling was kind enough to provide a long time ago.

Pics of your carb would probably help. But anyway, check into those things I listed, answer the questions I asked, and then Sterling will probably come along and solve the mystery before I even get back to this thread again. lol.

Sterling

"There is a screw beside the linkage to move the butterfly's open and closed."
-That's his idle speed adjust.
I remember the trouble you & I had trying to get your carb to idle well. Don't tell me you didn't know about the idle speed adjust screw!

IF this is actually a carb problem, you definitely have to define the "runs like crap" part with better detail.

Firstly I can say you definitely have a vacuum leak if you can close off the primaries completely with the idle speed adjust screw and it still runs at all. It's getting air in there from another source.

Secondly, you need to get a hold of some consistency while you're troubleshooting. Too many variables and you begin chasing your tail. The accelerator pump is adjusted with that nut you are familiar with; in (clockwise) makes a bigger shot, out makes the shot smaller. Just for starting out, there's a part of the lever linkage that is hinged inside the the pump housing cover with a pin. Adjust the nut so that the part that is pinned inside the housing cover is parallel with the housing cover itself.

Now take a look at your fuel bowl levels. If they are midway in the sight glasses (+/- 2 mm) then don't mess with your float levels.
Next you'll need to flip the top. If you have a flooding bowl you'll know right away if it's due to improper float setting if the float is hanging a lot lower than the other one while the air horn is placed on a table upside down on it's top.
If not, great. If you still have a flooding issue, then it's sediment in the needle valve.
If your fuel levels were not dead-on center, fix that later. It's not important at this stage. It will be down the road when you're fine tuning.

Now yank the jets on top (Just the jets). Take out the fuel jets. Check to see it they have been switched (I've done it; accidentally put the larger jet in the primary on one side of the carb and chased my own tail for hours).
Some of the air jets could be clogged, causing circuit transition problems. Visually inspect them, and clean them with carb cleaner if necessary. Hold the carb upside down, and spray carb cleaner into the circuits using the thin applicator straw that comes with the can. Spray down into the emulsion tubes (unless they can come out) while the carb is right side up. Any **** should come out the fuel jet holes into the bowls. Mop with a paper towel.
Don't look into the carb while you spray it! The carb cleaner gives a great money shot that never misses, and it hurts like hell!

Some of the orifices on the transition circuit jets are only a couple thousands of an inch, so it doesn't take much to clog them. When many of these jets clog, the circuit can't breathe and a siphoning effect takes place, over-richening the mixture and screwing everything all up.

Replace all of the jets, and before you pop the top back on, take a close look at the linkage and operation.
Are the valves all opening completely at WOT? If not, you'll have to adjust the timing by squeezing the wire that links the two linkages together tighter with channel-locks. I can't explain without pictures. You'll either figure it out for yourself, or if you can't you probably shouldn't be trying it.

Is there a good, even shot coming from the accelerator pump? First make sure there's fuel in the bowl behind the AP. If there's a problem, you'll have to pop the carb to fix it.
Close her up.

Now you're ready to find that vacuum leak.

Who modded your carb?

I highly suggest changing your fuel filter and your plugs.

Insane rx-7

iTrader: (1)

Sorry guys I should have been most specific

I will start off answering Kentetsu's questions. I am thinking of just replacing the plugs and distributor cap and rotor. I am thinking it maybe a timing issue I have had a problem similar that I couldn't figure out and all I had to do was change the plugs lmao. I also have already done your suggestion on checking the spray. It doesn't have a violent spray its more of a slow stream then a spray. Everyone talks about this FAQ's page but I have yet to find it on here?

Sterling this carb is a rebuilt nikki. My other carb was a Holley 500. I guess I don't fully understand the idle speed cause I thought it was that big screw above the mixture. The runs like crap part. Hmm It just sounds like the carb is trying SUPER hard and yet it doesn't raise the rpm's quickly. I shouldn't have used "crap" because it doesn't backfire or nothing it just doesn't preform if that makes sense. I will better clarify what happens when I turn that screw beside the linkage. When I turn it counter-clockwise it lowers the idle. ONLY to a certain point. When I get too what I think is almost closed it actually stalls the car. I have to open it up a bit to get it to idle. I did look at the floats before starting tuning and after I couldn't figure it out. Its hard to tell on the one side but they both look to be mid glass in the sights. I was going to try cleaning it if I couldn't get any farther with tuning it. I always change my filter when I start a new year with my oil change. Rob from rotary shack modified it. Its actually the carb off his car. Or one of them. He had some problems shipping me a carb so he had to give me one of his.

I know you guys get bugged a lot on here about carb issues and I feel bad for bugging you myself. I think my main issue is just having a point to start from. Like where the linkage or idle speed by the linkage should sit then I could play with the acc pump to get it running right I think. It might be timing though. I am thinking its most likely the linkage though. Cause as I most the screw to bring the idle down it changes where everything comes into play. So I have to figure out how to adjust that so the secondaries come in and the acc pump.

I really appreciate the help guys. I hope I answered your questions well enough to receive a answer without wasting too much more of your time.

Kentetsu

FAQ = https://www.rx7club.com/1st-generation-specific-1979-1985-18/1st-gen-rx-7-faq-page-237777/

Sterling- he mentioned the idle mixture screw, the idle speed screw, and this other screw that changes the position of the butterflys. That's what threw me off. And of course I know where the damned idle screw is! lmao.

So anyway, yeah, the idle adjustment screw is the one closest to the firewall.

And yeah, it kinda sounds like the way one of my old carbs was acting when I had a couple of clogged jets. Have you asked Rob about it?

Sterling

Just makin' sure.

My thoughts exactly.

Insane rx-7

iTrader: (1)

Rob is SO busy all the time lmao. I will get in contact with him one day. As for right now I am doing a transmission change in my driveway. And can't run the car and adjust anything as of right now anyway. Everyone thinks I am nuts for doing this in the driveway. But I wouldn't pay someone to do something I can do myself. When I get a hold of Rob I will see how I make out and get back to you if I still don't understand whats going on.

Thanks for your help so far guys.

Insane rx-7

iTrader: (1)

Ok I got the damn car off the jack stands. The transmission is in! I replaced fuel filter + plugs + cap + rotor + oil. Start the car the tranny seems to be ok but I got a little vibration. Not sure if its cause I replaced the clutch. But anyway the car wouldn't idle below 2,000 now. I can take the idle adjustment all the way out and the speed screw all the way in I am guessing its the timing now? I can't see what else it would be. If anyone can help I would be great full.

thekyl

Its very sad I'm in the same boat right now. My car acts almost the exact same way I can get it to run but I have to hold the pedal at 2K plus or it wont run. tweaking everything back and forth I get nothing. I cleaned the carb and moded it per Sterlings instructions in the FAQ, but still nothing. Its not a perfect mod but I have everything disconnected emissions wise. only thing different is this is a 12a in the GSL-SE car. I have a FPR limiting fuel at various levels with no help on any setting. Only thing I have not done is change the plugs this last time (3rd set so far) after you fix Insane's car im sure it will be something close to that on mine as well.

Insane rx-7

iTrader: (1)

thekyl If your car won't idle without holding the pedal down its probably a vacuum leak. I had mine idling and when I replaced all the stuff with new stuff it went all wack. I am not a master when It comes to cars. I pretty much learned everything from just looking at something and figuring out how it works. But I am not stupid either. What I have been told is a car will never idle with a vacuum leak. Your vacuum at idle should be maximum.

thekyl

humm kk sounds good I will see what I can do its got to be some where in there

thekyl

well i'm a dope I think I have isolated the problem to a bad water jacket o ring in the intake. while its running my coolant is slowly going down. while just sitting after 48 hours I have a small 3" wet spot under the car on the intake side. At least I hope this is it. I think the water intrusion is keeping the plugs wet and not letting them burn the fuel properly. That sound about right? I checked the archives and searched and no one has reported this exactly causing a problem, but I think that might be where my vacuum leak is coming from. I noticed there is a small amount of coolant below the carb on the intake. I cleaned it off and after sitting for 15-20 min the little 2" puddle is back. Tonight going to pull the intake and replace the O-rings to see if that fixes the problem. I will let everyone know.

bliffle

Listen to what Sterling says. I archived this valuable comment on my computer.

Insane rx-7

iTrader: (1)

Ya those damn o-rings can be a pain in the ***. I read a bunch of forums on here in the FAQ's page. And apparently my carb is setup properly. I took sterlings advice and got someone to help me with the throttle cable and I haven't drove the car yet, going out in about 10 mins to see if It fixed my power issue. I also took it to my buddies and we set the timing perfect. Also I tried finding this venturi vacuum that the timing advanced is coming off of and my vacuum gauge won't pick it up so I don't know what to do about that crap. Anyway I will tell you what happens. Oh it idles now! I think timing was a bit issue with my idle.