Hello everyone, I have a 1973 cb500 with a hanging idle issue. I have searched around the forums for other answers but this brings questions of my own.
Situation:
Bike idles fine at 1000-1100 rpm. When I give it throttle, the rpm will jump and hang there. It seems to jump right up to 3k rpm even if I just give a little bit of throttle and close immediately. It will hang there for about 2 seconds then drop back to idle. It seems to drop back to idle a bit slow, but relatively close to normal.
I've tried spraying around the boots and intake around the engine with WD-40 to check for air leaks. Not sure if WD40 is able to be used for that, but I had run out of carb cleaner. There was no change in idling from what I could tell
I have set the cam chain tensioner and adjusted the valves. I have not looked at anything on the timing yet, but I don't see how slightly off timing would cause this running issue. Unless it's the advancer, but I'm not really sure of the symptoms of a stuck advancer.
Everything on the bike is stock. 4-4 exhaust baffles in-tact, stock airbox stock paper filter. Stock jets, stock needle position (2nd from bottom) and air screw 2 full 360 degree turns from seated. The carbs are 627b I believe, and the american stock settings were different that the european setting being 3rd needle clip position and 1 1/8 turn on the screw.
Other forums have also said to check the float level with a clear tube but I am not sure how to do that with these style of drain screws as the fuel doesnt come out the nipple on the bowl.
Any help is appreciated, thanks