QuestionHi Bill,
I am a brand new rider with a 1975 CB360. It is a "fussy" starter, and floods easily. This morning I started it and it idled properly. I shut it off and went to grab my helmet in the house. When I came back out and started it, it revved to 4000rpm and stayed there. I tried to move the throttle cable to see if it was stuck on something, but it didn't help. I waited a while, then twice more I started it and the same thing happened. What could be causing this? And - is it something I can fix myself? I'm a total newbie to motorcycles, but I used to be pretty comfortable working on cars back in the day. It seems so odd that it just happened out of the blue like this.
AnswerChristine, the general causes of high idling are vacuum leaks, due to damaged carb diaphragms, intake manifolds, incorrect timing, pinched, misrouted or decaying throttle cables and other external issues. There are some models that have an problem with the choke connector link contacting the throttle cables, but that was more for the 350 and 450s, I think.
If you don't mind resetting the ignition timing again, you need to probably remove, clean and reinstall the mechanical spark advancer, behind the point plate. Sticky advancers are often the culprit on high rev situations at idle.
You can try to mark the point plate position carefully, then remove it, remove the bolt on the end of the camshaft, which holds the advancer, then mark the advancer/point cam relationship (you can get it off 180 degrees), then pull the advancer, remove the point cam, clean and lube the shaft and the point cam bore, then reassemble it all again. The grease gets gummy and/or corrosion sets in.
Be sure that the left side points open at the LF mark on the flywheel and the right side points open at the F mark. When you pull the cover on the left side to access the rotor/flywheel, it will drip some oil out, so do it over a drain pan and when the bike is on the centerstand.
Bill Silver
Take the MSF training class! :>)
