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Still running rich at 5,000 ft elevation w/ smallest jets

Fuel System: Gas (Petrol) tanks, Carburators
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GG Member
Posts: 138
Joined: Tue Apr 13, 2010 10:45 pm
Location: Costa Rica

Still running rich at 5,000 ft elevation w/ smallest jets

Post by GG » Sat Oct 01, 2022 8:13 pm

Hello all,

Advice and experience welcomed. My 1966 Superhawk, well cared for, has always run well. I had to replace the head gasket, honed cylinders, new rings and while apart I went through the carbs - but all was very clean. I'm running a 120 main and 35 low jet. With this jetting I could pass smog inspection in Costa Rica. Now the bike is running super rich, both cylinders, "2 cycling" from idle up to 4,000 rpm's. Air screw doesn't make enough difference. Sometimes fouls a plug. Float levels perfect (I attempted to lower the fuel level but that wasn't good).

I understand that there aren't any smaller low jets than 35. If I go lower on the main jet than 120 will this help the rich condition at lower rpm's? It runs fine at higher rpm's - pulls good.

I'm not sure if the new rings are "sucking" that much more than before that it could have changed so much. All the "normal stuff" is perfect - timing, valve adjustment, cam chain, etc.

Has anyone had this experience and fixed it? :-) Let me know! Thanks.


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