1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

New FB owner: Surging under constant throttle

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Old 02-01-05 | 01:00 AM
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New FB owner: Surging under constant throttle

Hello rotary fans. I've been out of the rotary scene for a while after the motor in my FD3S blew up on me. Anywho, i just purchased an 83 FB with only 55K miles on it.

the only mechanical issue with it currently is that it surges (very slightly) under constant throttle (coasting at say 40mph).

I saw the FAQ about surging with the SE models (EFI) but nothing about carb models. Anyone have ideas what it could be before I checked around? Loose hose in the rats nest?

Currently, the surging is bad enough that It won't pass smog as it can't maintain a constant RPM on the dyno.

Thanks
Old 02-01-05 | 02:58 AM
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It sounds like it is running lean.
Old 02-01-05 | 10:05 AM
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that sounds about right actually, i never stopped to thinkn about the fuel mixture. Are the carbs on these things slightly adjustable with an air/fuel mixture screw to compensate?
Old 02-01-05 | 10:26 AM
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see this post with pictures =)

https://www.rx7club.com/1st-generation-specific-1979-1985-18/i-need-know-idle-control-screw-mixture-screw-381065/
Old 02-01-05 | 01:12 PM
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thanks zyrano, it seems that just changes the mixture below 2000rpm or so. i guess to change the mixture past that i'd need to redo the jets. would some techron carb cleaner help?
Old 02-01-05 | 03:29 PM
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k, i did more searching, and it seems like the sputter valve is a prime candidate.
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