Motorcycle Repair: 1981 Yamaha Virago XV750 wont start on a hot engine, carburetion, gas cap


Question
The bike will start right up when leave it over night or for a few hours parked some where. When I drive a couple of miles to the gas station and try to start the bike again, then it won't start AT ALL! It will turn and turn until the battery is dead but will not start. I have tried using the choke but that doesn't help. I have gotten used to push starting the bike...it usually starts right up when I am giving the bike a solid push for a few steps while it is in 2nd gear.

Yesterday, I drove hard around 150 miles and had to fill up gas. I was dreading having to push it but I actually didn't have to! It started right up. So the problem is only when I drive around town and stop at the ATM or for gas, when the engine is hot, it won't start.

I have cleaned the carbs and fuel system last summer. The problem was prevalent then as well. The battery was changed last summer as well, along with the spark plugs. There is very small hole in the diaphragm in on of the carburetor, it can only be seen when put against the sun. This shouldn't be a problem, it just gives a bit longer delay in the pick up at lower RPMs.

I am not too sure what the solenoids do, or the electrical system in general. Everything seems fine, that is why this problem is just irritating me so much!

Answer
You can't even start to try to repair this bike with a "There is very small hole in the diaphragm in on of the carburetor, it can only be seen when put against the sun. This shouldn't be a problem"
The carburetion will not work at all with a hole in the diaphragm. These are cv carbs and they rely completely on the intake pulses of the motor to activate them, a hole will make it lose this action and the engineers that designed them didn't allow for holes in their diaphragms.... replace the slide then resume diagnosis.
Is your gas cap vent plugged ? check this also...