Gas tank pressure

[Boss Hog]

I have a "63 MF 35 that seems to build up a lot of pressure in the gas tank. After running it for a while if you take the gas tank cap off a LOT of pressure blows out.

If I shut it off hot and it sits for a few minutes, the pressure forces fuel past the needle valve and floods the carb. It takes quite a bit to get it started again.

The fuel tank cap appears to be vented. But maybe it only allows air to go in, and not out? Or maybe it"s defective?

Just curious if anyone else has dealt with this before.

 

[Anonymous-0]

should vent both ways in and out replace it

 

[Don Hooks*]

Marlowe is right - I put an automotive cap on mine and, even though it is vented, it holds 3 or 4 psi for emission control. It caused exactly the same issues you described. I put the old beat up cap back on after the first carb overflow and it has been fine since.

 

[Boss Hog]

Thanks guys - I'll give a new gas cap a try.

Might take a while, as there isn't a dealer near here. Maybe I'll try drilling a small vent hole in the old one to get by for a bit.