Motorcycle Repair: 1984 Honda Shadow Starting Problems, rubber diaphragm, nylon screen

Question
Hello Bill,

I have a VT500C Honda Shadow that has a hard time starting. It will drain the battery trying to start but once it does it runs fine. Also if you ride the bike for a while and stop it will not start until the bike has had time to cool down. I have already replaced the battery but that has not helped any. My next try was going to be the started. Do you have any suggestions?

Thanks!!

Answer
Doug, it is a good idea to have the valves adjusted first, and have the compression readings verified. That way you know that you have a sound engine to continue to troubleshoot.

The carburetors have enricheners that open ports that add air and extra fuel for cold starting. Be sure that the cable and enricheners are working properly. If you take the carbs off, you can drill out the cap for the idle mixture screw, so you are able to clean the passage properly and then make adjustments that suit the engine afterward.

If the carbs haven't been off (for awhile or ever), it is about time to have them inspected and cleaned properly.

You need to determine if the cause is no spark or lack of fuel, when it won't start.

http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-vt500c-shadow-1984...  FUEL TANK....   look at the petcock diaphragm. Apply some vacuum to the diaphragm to check that the rubber diaphragm is not torn or has a pinhole. If this part fails, you get an air leak into the intake tract, plus it shuts down the amount of fuel delivered to the carburetors.  There is a nylon screen on the end of the petcock up inside the fuel tank that can get plugged up, so it is worth a check.

If you discover that you are losing spark to the engine, instead of fuel then you have to look at the pulse generators near the crankshaft and then the spark module.

Bill Silver