QuestionI have a 81 Honda CB650. The bike will stall once it gets hot (after about 15 miles) and will not start again until it cools off. If I change the plugs it works fine for a while but then eventually returns to stalling. As long as I stay on the throttle, its fine, but as soon as I have to slow down it will stall. Thanks in advance for any help
AnswerRyan, there are many possibilities for stalling/idling issues.
Start with doing a basic tune-up check... adjust valves, check compression to be sure that you have four strong cylinders to fire.
These models have an automatic fuel valve system that can have vacuum leaks at the diaphragm, causing limited fuel flow to carbs as well as a vacuum leak into the connecting carburetor port.
There are two spark modules back by the battery that are known to give problems. Check for drooling black tar on those units.
The charging systems fail, often due to defective rotor designs, which can limit output and burn up the rectifier/regulator. These are battery powered ignitions, so when the power goes low, the ignition system fails. You must have a fully charged battery in the system at all times.
Carburetors may need a good cleaning, especially the idle jets.
Spark plug caps should be in the 5k ohm range, disconnected from the wire ends.
Your petcock screen could be plugged up. Gas cap vents need to be checked so that the tank can breathe properly, otherwise you get a vacuum in the tank and no fuel flow.
Bill Silver
