Hello all,
I'm not sure if I have a problem with my standard Mikuni fuel pump. My bike is a 1990 3AJ on 77,000 miles.....the bike has been a bit difficult to start lately and I was thinking it was a fuel related problem. When it starts and runs and pulls nicely in all gears. After it starts I have no problems re-starting it. My questions.....
1) I took off both fuel supply lines from the tank and the fuel feed line to the carb and blew through one of the fuel lines from the fuel tap...I was able to blow ride through the fuel lines and the pump....should I have been able to do that? I thought the valves in the pump would prevent that??...is that right.

2) When the tank is roughly 1/3 full if I remove the fuel line from the pump to the carb' I get a dribble of fuel come out and even when cranking the engine I don't get much more than it. When the tank is full and I pull off the fuel feed fuel line fuel gushes out...as if gravity is forcing fuel straight through the pump and all over my fingers. Should the pump valves prevent that?

I'm not sure if there is a problem with the pump that is being masked by having a full tank of fuel and gravity is supplying the carb. But when the fuel tank quantity is low the flow is not so strong and the fuel supply problems become obvious.

Thoughts?.....

Thanks,
Andy