dies in the heat

[brew]

i have a 79 standard and my bike seems to stall when it's hot and it has been sitting outside. It will actually start fine and idle, but when i get on the throttle and drive away, it starts hiccuping and riding really rough. it will usually die if im not alreaidy driving fast enough. If it doesn't die, it will ride out within about 100 yards and then its smooth as glass from then on. If it dies on me, i have to pull out the choke and it will fire up really rough. I have to get it moving and again, within 100 yards or so it will be fine.

This only happens on hot days. It didnt happen at all during the winter, but now that the summer is back, i want to figure this out. When i walk up to my bike when its hot, i hear hissing coming from the fuel cap. I know there is a pinhole breather there. Could that be clogged and causing a vacuum issue? if so how would i clean it out? any other possible ideas? i have tried running sea form through the gas several times. i havent changed my fuel filters in a while. maybe that could be it. any help would really be appreciated.

[bikerphil]

cap

The vent in the gascap can be cleaned by taking the small screws out. Make sure it is clear. Check fuel flow.

[prometheus578]

Sounds like the vent is restricted

Hot weather... fuel in the tank expands. Trapped air can't freely vent, so the cap whistles.
Partially plugged vent causes a vacuum in the tank, fuel won't freely flow to the carbs. At low speed, a low, slower moving volumn of air passes through the carbs and picks up fuel from the pilot circuit. If the bowls aren't full to the right level, it will have a hard time picking up fuel. Higher RPM, faster air flow through the carbs, and bigger jets for the other fuel circuits will pick up this lower fuel amount easier.
Using the choke/enrichener to restart provides the fuel that it isn't getting.
Take the gas cap apart...
Clean your vent hole so you can pass gas like the rest of us.