1979 CB750K idling too high

Posted by boesen34 on Aug 06, 2012; 8:27pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1979-CB750K-idling-too-high-tp4026531.html

Hello all,

I have just finished rebuilding my carbs for the first time. All seems to be well, other than a high idling RPMs after rolling on the throttle. I have adjusted the throttle screw under the carbs, and the bike idles properly (or close, around 1000-1200 RPM) when the bike is first started. However, as soon as the RPMs exceed 4000 or so, they do not decrease, even with the throttle completely closed. I've checked the throttle cable and choke, and each of those seems to be working properly. The choke is not stuck open.

The bikes RPMs are fine when riding in gear once the clutch is completely released, but as soon as the clutch is engaged or it is shifted into neutral, the RPMs return to about 4000.

My initial thought was that the choke was stuck open, but that does not seem to be the case. I've had the bike for about a month, and I only have about 3 weeks of experience working on it. I may be missing something entirely obvious. My guess now is that something is sticking and not returning to its normal position, but I don't know where to start looking. I may have even caused something myself when rebuilding the carbs. Also, I have not synchronized the carbs since the rebuild (sync tool is in the mail), would this affect the idling speed like this?

Any advice or ideas would be much appreciated! Thanks!