gas leaking from exhaust manifold on start up

[oliver dicicco]

Hi

This has been an on going problem. The bike is a 98 M900. The bike was leaking gas into one of the cylinders, after it sat for a day or two. On start up gas would drip out of the exhaust mainfold where it met the slipons. On several occasions the starter motor wouldn't turn over, until i rolled the bike in gear to force the gas out of the cylinders.

Took it in to the shop, they replaced the needle valves on the floats, and confirmed the vacuum petcock was working normally, there was gas in the oil, so the oil was changed as well. There was no evidence of gas leaking out of the overflow tubes, just the manifold.

Get the bike back runs fine for about a week, leave it over night, same gas leak in the morning. Back to the shop, pull the carbs, they say there is dirt in only one of the float bowls, replace the fuel filter at the tank, and add a second in line filter after the fuel pump. Bike is fine for two days, leave it over night, same leak on start up. Back to the shop, they now have the carbs on the bench with a fuel line attached, not leaking now.

Any ideas on why the bowls are draining after the bike has been sitting?

Thanks.
O

[bigiain]

Has the fuel pump been checked? Split diaphragms in the pump can leak fuel into an inlet manifold - that might be why you cant find a leak in the carbs... Pull the vacuum line for the fuel pump and see if it's got liquid in it.

big