I need assistance from the current forum carburator geniuses. My mechanic removed the Racing Beat Holley carb and header, rebuilt the stock Nikki carb on my '84 GSL and reinstalled it. The engine is bone stock now. He encountered what he described as a a serious stumble at 1800 rpm. He replaced the accellerator pump with a different accellerator pump with no improvement. He called some local Mazda dealer and was told, nobody there works on rotaries! Can someone suggest a possible cause and cure for this?
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It may not be a technical answer, but when I rebuilt my sat for 5+ carb, I had a similar result. I took it apart and thoroughly cleaned everything again. Reassembled. That took care of the issue.

 

+1 on Cookboys advise. Sounds like it needs to be cleaned really well.

 

Most likely something gummed up that got missed during the rebuild, as cited above.

Exact year and model of the carburator itself would help, Fed, Cali, or Canadian, & is it the original from the car? There are a number of variant Nikkis out there.

I'd lean toward a clog in the transition circuit or a primary main air bleed, but that's just guesswork.

 

The carb is original to the car. Nikki fed spec 84 GSL. The stumble actually occurs at 1500 rpm. How can I tell which model Nikki it is? My VIN shows that the car was manufactured in October of '83

 

There's a very useful reference available from Sgt. Fox's manual archives, called the 1979-85 Carburetor Manual:

Foxed.ca - Mazda RX-7 Manuals

It goes into great detail about the various carb builds and what differs. Invaluable reference any time you're working a first-gen carb issue!

Based on it, it looks like by 84 Nikki was down to only two variants (auto and manual trans).

You're lucky; 1980 had 6 variants!

 

Thanks for the replies. I actually provided him with the carb manual before he started as well as the FSM, wiring diagram, service bullitins and anything else I could find on an '84.

 

When I was having my issue I either read about or was told here about the transition circuit. That is what prompted the re rebuild that cured the problem.