Won't run with gas cap on...

anachronism

New Member
Joined
Mar 20, 2008
Messages
4
Anybody have this problem? I built one of what I am assuming are known as the "happy time" kits.

It has been running great, except for one issue- With the gas cap on, the engine will stutter after a few minutes. Opening the gas cap resolves the issue. It seems that the gas cap is making an airtight seal, creating a pocket of suction at the top of the tank that keeps gas from flowing down the line.

Any suggestions to resolve this?
 


H

HoughMade

Guest
You have correctly identified the problem. It needs a vent of some sort. A 1/8" hole in the middle of the cap works, but some fuel may splash out.
 
B

BSA

Guest
Hello anachronism and welcome to the forum. Please introduce yourself in the correct section so that we can all say Hi.;)
 
L

Large Filipino

Guest
I have never heard of a stock happy time gas cap doing that. That must be a really good seal. It's supposed to vent. On your cap do the thongs that hold the cap in place give way to the springs inside?
 

sparky

Active Member
Joined
Mar 19, 2008
Messages
1,429
Is it possible to pressurize the fuel system on a happy time? If you got a new carb or something, would it be fairly cheap & easy?
 

fastboy9

Member
Joined
Jan 22, 2008
Messages
585
Ye this was happening to me as well, I just drilled a small hole in the top of the cap as a 'breather', most dirt bikes have these. That will sort out the vacuum problem out straight away
 
Top