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

[GG]

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.

GG

[marzini]

Soggy air filters?

[Tim Allman]

I think you have a problem that isn't due to jetting. The standard main jet size is #135 and the slow jet size is #42 which are both much bigger than what you are using. Since both jets meter fuel (not air) your engine should be running very lean. You should check that you have the correct needles with the spring clips in the middle grooves.

Here are two links to a couple of documents that you might find useful. I wish I could be of more help.

https://drive.google.com/file/d/1FS1AkO ... sp=sharing
https://drive.google.com/file/d/1C8PRPy ... sp=sharing

[marzini]

120 main and 35 low jet

Hi GG, I have a little experience with your symptoms. At 6300' in Santa Fe, my CB77 is running 130 mains, middle (D9) needle slots and 38 slow jets. It is a little lean, mainly due to worn jet needles.

As for carburetion changes due to more or less compression (rings), I have found that WORN rings DO result in a rich condition necessitating a leaner jetting combination, because the engine is sucking less air. Your new engine's performance characteristics would normally produce a LEAN condition, if that was the case, so no help there.

4 into 1 Honda Parts sells JIS thread main jets down to 120, but, as Tim suggested, the problem isn't jetting, it seems.