Join Date: Nov 2009
Location: Lander, Wyoming
For fuel to be sucked down the vacuum hose to the carburetor, both diaphragms have to have failed & the atmospheric air vent/weep hole in the gray plastic separator disc would probably have to be plugged, otherwise wouldn't fuel leak externally thru the air vent/weep hole?
If both of the diaphragms are GOOD and the air vent/weep hole is plugged, could it be that the diaphragms retract enough with lowered vacuum of partly open throttle to restrict fuel flow such that the float bowl does suck dry? With the higher vacuum applied at cranking speeds with a closed throttle plate & at very low throttle openings the float bowl might re-fill/stay filled? In this scenario, a simple disassembly and cleaning of the diaphragm assembly may be all that is required.
But this still does not address the possible temperature issue.
Modify at "YOUR OWN RISK"!
Still riding my 1987 KL650-A1. 85,000+ miles & counting