Hello,

I recently acquired an 05 c90 that’s in decent shape with 20k miles. Bike handles and functions like it should.
I went to fill it up for the first time the other day and after I parked it I started seeing drops of gas coming from the bottom and it wasn’t coming from the drain tube. I took the seat off to find out the fuel pump was leaking. When I opened the gas cap a lot of pressure was released.
After pulling the fuel pump to inspect the oring it still looked in good shape. That led me to believe the vent was clogged and it over pressurized the fuel tank. The vacuum canister and check valve were not blocked and the vent line going to the filler neck was not blocked either.

I’m lost as to why these tanks build so much pressure and if I should just let it vent to atmosphere. (I didn’t overfill it either)

Has anybody heard or seen any issues with this? Should I just let it vent to atmospher?

 

I think I may have figured this out. The check valve I tested only flowed in one direction. After looking at parts diagrams its a DOUBLE Check Valve, the check valve should allow vapor flow in both directions but should only stop when fluid (gas comes in contact with it) to avoid fuel spilling in a tip over. I will post back an update after I get the new gasket in...

 

Final update, after removing the check valve bike runs great. Went for a long ride and zero pressure built up when I removed the gas cap. The charcoal does a good job of filtering out the gas smell (dont notice any lingering fumes). Glad this was an easy fix by just taking the 2 way check valve out of the vent line.