Sorry if this is long and quite descriptive, but it may be necessary. The symptoms: As the bike warms up, it will slowly die at idle. At higher temperatures, it will die quicker it seems. Within the last 100 miles, I have cleaned the carbs and adjusted and inspected the carbs. The choke is fine, the carbs are roughly synced, no professional equipment. Idle adjuster works, new spark plugs, coils, regulator/rectifier, starter. The air filter is clean and new, pilot screws are adjusted, fuel line is unobstructed. After the bike dies on idle, it will start back up, more difficultly than cold, but will still start. After reading through my manual, I noticed that incorrect valve heights could cause the bike not to idle properly. Does anyone think that it's worth pulling the heads to measure the heights? Also, If I raise the idle, the revs begin to hang after I blip the throttle (around 3k) and will eventually drop down and die. Please let me know what you think it might be if not valves, and if possible how to test the culprit. Thanks in advance, sorry for long post.
Hanging idle is usually either an air leak or the carbs are badly synced. Spray WD-40 around the carb boots and see if the idle changes, if it does, then you have an air leak around the boots - tighten the clamps or order new boots if the leak does not go away. The float height you reference is the carb bowl float height. The red two-pod plastic piece in the carbs are the floats. The metal tang rests on the float valve needle. The valve needle has a spring loaded post where the tang hits the needle. To adjust, you angle the carb until the float tang "just touches" the needle post. At this angle, measure from the edge of the carb to the topmost part of the float and then bend the tang to change the measurement. When bending the tang, very little change goes a long way. If you don't have the means to sync the carbs with gauges, you can do a pretty accurate bench sync using a 3/32" slip of paper. Use it as a feeler gauge between the carb bore and the throttle plate. To ensure an accurate measurement, place the paper as far from the plate shaft as possible. Loosen the idle screw until it is not touching and bench synch the carbs in order. Once synced, tighten the idle screw until it is touching and then turn in 1 complete revolution.
Thanks for the sync advice, but I must apologize for my ambiguitity. When referring the valve height, I meant intake and exhaust valves. Float valves are all in check. So my question is can improper intake/exhaust valve height and/or timing cause the idle to die. I have already checked for vacuum leaks, all fine. Thanks.
Alright, so I did a valve height adjustment and the performance is noticeably better, however, the symptoms are the same. Engine will race to 3k or stumble around 1k and die. It doesn't die right away, as it gets hotter, the idle will drop. I can keep it alive if I keep upping the idle, but then when you give the slightest throttle, it races to 3-4k and after a good amount of time will drop back down, and die if it gets hotter. The engine has trouble cranking on startup if it is still hot. Sounds like the battery is very weak, but will start in an instant cold. Not a California model. Where else could there be a vacuum leak besides the carb boots and head gaskets? Please Helps?!
