Nikki Carb Issues... Help?
 

Car: 1985 RX7 GS (Nikki Carb)

The car isn't running perfectly. After not being driven much at the dealership I bought it from the Accelerator pump was leaking gas and it would bog when getting on the gas to take off or accelerate semi-rapidly when cruising. I used the various tutorials to take the carb off and change the Accelerator pump hoping that would solve my issues.

It isn't leaking gas anymore (thank God) but there is still a hesitation when I blip the throttle too quickly or go from zero throttle to about quarter throttle all at once. It doesn't seem like this would be normal even though I realize carbureted cars don't always operate as perfectly as FI cars. If I drive the car nice and smooth and take care not to jump on the throttle too quickly it runs pretty darn good. Revs right out to redline and above easily. Just wondering if the hesitation symptom is kind of normal or if I am definitely experiencing an issue.

Gas: 91 Octane BP with roughly 1/2 oz per gallon of premix TCW3 2 stroke oil from Walmart

What I have done to try fixing it:

1: New spark plugs
2. New plug wires
3. New Distributor Cap and Rotor.
4. Accelerator pump replacement.
5. Various different fuel mixture/idle settings

Just as a side note I don't remember the car really having any sort of hesitation before I started premixing it, but I was driving it very gingerly so I may never have noticed it during the first tank I drove through. It doesn't seem likely that a fairly conservative premix should be causing an issue like this but I have definitely been wrong before.

Hope someone can help :)

Don't use 91, get 87 or lower. Rotaries don't need/want high octane.

Did you rebuild the carb when you fixed the AP issue? Did you adjust the AP? You may just need to adjust
it. If you rebuild, don't use the new needles or seats.

Hey thanks for the Reply. No I did not rebuild the entire carb because I don't have a full rebuild kit for it. I was curious about adjusting the AP but my Haynes manual didn't say anything about how to do it. Furthermore a search didn't yield much info on how to do it (or if it could even be adjusted...) any chance you would be able to explain it?

If I remember corect there was a linkage underneath with a spring, so I'm just guessing I would need to adjust something on that maybe?

Also, since it only seems to stumble when I blip the throttle past about 1/4 throttle or when trying to take off quickly from a dead stop would that seem to indicate it is pushing too much fuel and momentarily flooding the engine when I do that?

You can test the accel pump system by taking the air cleaner off and watching the nozzles of the accel pump jets as you blip the throttle. They should visibly jet fuel. If they do, then your issue likely is elsewhere.

If they don't, double-check that your pump linkage is set up right.

If it's correct but still no flow, it's likely that the circuit is clogged - - the check-ball and weight system that lets the pump work can get varnished up to the point that no fuel flows.

It's possible to clean that path out without rebuilding the whole carb, but you would need to remove the carb so you can turn it upside down at one point.

Before going that far, judicious use of carb cleaner or a fuel additive like Seafoam might loosen them up.

Thanks for replying! I will try all of that when I get back home from vacation. I really want to get the car running right. If that means taking the carb off again than so be it. I'll check to see if its squirting gas first and then take the carb off if I need to.

I'll also run some gumout carb cleaner through the next tank of gas.

By the way awesome car! That thing looks exactly like mine!

Hey, I'm having a similar issue with my Stock 12a 1985 GSL. If i'm not very gentle applying the throttle when the car is idling, it will stumble. If I stab the throttle it will stall. Once I'm moving or the engine is above 1500 RPM there is no indication that anything is wrong at all.

I'm intending to check and see if I can see fuel squirting into the carb as was suggested.

How does one check this? how would one know if the pump linkage is correctly set up? What reference would you use? All my previous fun machines were fuel injected so I don't really know by looking when something "doesn't look right" on a carburetor :(

That statement, to me, is shocking and upsetting. But we're in the future now so I just have to lay back and accept it.

Go you here:

Foxed.ca - Mazda RX-7 Manuals

Scroll down to the section marked "Other," and DL the 79-85 carburetor manual. It's very useful.

Carbs, like RWL tires and big hair, are so 80s man! Dig it.

Incase anyone is curious I tested the Accel pump and it seems to be working fine. Squirts plenty gas whenever I hit the throttle. I'm starting to think the carb probably just needs a thorough cleaning honestly (shocker). I am going to purchase a second carb cheap from a friend and go through that one so the car doesn't have to be fully out of service for a couple weeks while I clean the carb.

I am a little curious if you think my premixing could be part of the issue though. I went and got TCW3 premix oil for it from Walmart. Its just the cheap stuff, not amsoil or anything. Anyone ever had a bad experience using cheap premix oil in these cars? I plan to go get a better brand oil soon but thats all I could find near me at the time when I bought the car, and no way was I going to put faith in a 32 yr old OMP that had been sitting for like 3 years... currently premixing about 1/2 once per gallon.

That oil should be fine. I know folks that premix with it all the time and no issues.

If anything, premix probably helps prevent fuel evaporation and varnishing by a tiny bit. It's such a small proportion of the fuel volume, though, that it shouldn't bother a carb at all.