Ok, I know you guys think I'm a crackpot posting all these weird symptoms. I'm a magnet for weirdness... I never did find anything to use as a gas cap gasket for my Honda CB125S. Then I discovered that a mouse pad is neoprene and is gas resistant, after the glue softens and the cover comes off. So, I made a gas cap gasket out of a mouse pad. When the tank is full, it works great. Not a drop leaks out. As the tank approaches empty, gas starts to leak out of the cap. I fill it up and the leaking stops. I've done this several times and it's absolutely repeatable. I can't get my head around how this can happen...or what to do to fix it. mike -- Return address is VALID. Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. Compaq Aero floppy,ram,battery. FT-212RH 2-meter 45W transceiver. 2-meter linear Toshiba & Compaq LiIon Batteries, Test Equipment 30pS pulser, Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/
Gas cap vent plugged / restricted ?...Just shooting in the dark here as it sounds too weird to happen <LOL>
When the tank is full, there is little to no airspace to become pressurized. As the tank empties, the airspace increases and the tank becomes susceptible to pressurization. Altho usually it's usually a negative pressure(vacuum)if the tank cap isn't venting. The the bike stalls and won't run because the head pressure of the amount of fuel left in the tank can't overcome the negative pressure in the tank and the carb looses it's gravity feed. Now if the bike sits for a while with a low level in the tank, especially in the sun, the tank will become pressurized positively and you'll get a rush of air escaping when you remove the cap. The cap is supposed to vent positive and negative pressures, keeping the tank at atmospheric, so as was suggested, I would be looking at the cap venting mechanism itsself first. Trailryder42
I'm not sure I buy that. The pressure developed by vaporizing liquid should be pretty much independent of the volume available. More gas sloshing around in the tank should increase the possibility that liquid gets into the vent. I'm observing opposite behavior. I do agree about the negative pressure developed by draining the gas, but that should suck air in thru a leaky spot, not spray gas out???? As the tank empties, the airspace increases and the tank The the bike -- Return address is VALID. Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. Compaq Aero floppy,ram,battery. FT-212RH 2-meter 45W transceiver. 2-meter linear Toshiba & Compaq LiIon Batteries, Test Equipment 30pS pulser, Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/
