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59096 · February 21st, 2019, 01:58 AM

After cleaning the carbs and setting everything up to the book my 89 GPX250 still would not idle satisfactorily when hot. When cold OK but when the engine was fully warmed up it would remain at 4000rpm after stopping for 15 seconds or so and then drop back to around 1300rpm at which point the bike would stall if I tried to increase throttle to take off again. Adjusting the idle with the thumbscrew only served to make the problem worse as small adjustments caused it to either rev too high or stall. These seem to be sysmtoms that many people with these bikes on this site and other similar sites seem to experience. Fortunately I seem to have managed to improve this problem although not to have eliminated it. My air screws are now at 4.5 turns out each and I did discover several slightly loose screws holding the caps on the diaphragm on the LHS carb. The bike will still hang up slightly on stopping but returns within a few seconds to a steady 1300RPM idle. It does not stall now when idling but some care is required when taking off again as it requires a gentle touch getting the revs above about 2000 before dialing in the throttle. As before the idle adjustment thumbscrew is pretty useless and I am wondering if this ‘fix’ has as much to do with cooler weather as much as anything else. Only real difference is the air screws out fron 2.5 to 4.4 turns and some tightening of a couple of loose diaphragm cover screws. What do others think?

February 21st, 2019, 01:58 AM	#1
59096 ninjette.org member Name: Garry Location: Bungendore Australia Join Date: Jan 2019 Motorcycle(s): GPX250 1989 model and 1990 model Posts: 98	Idle problem improvement After cleaning the carbs and setting everything up to the book my 89 GPX250 still would not idle satisfactorily when hot. When cold OK but when the engine was fully warmed up it would remain at 4000rpm after stopping for 15 seconds or so and then drop back to around 1300rpm at which point the bike would stall if I tried to increase throttle to take off again. Adjusting the idle with the thumbscrew only served to make the problem worse as small adjustments caused it to either rev too high or stall. These seem to be sysmtoms that many people with these bikes on this site and other similar sites seem to experience. Fortunately I seem to have managed to improve this problem although not to have eliminated it. My air screws are now at 4.5 turns out each and I did discover several slightly loose screws holding the caps on the diaphragm on the LHS carb. The bike will still hang up slightly on stopping but returns within a few seconds to a steady 1300RPM idle. It does not stall now when idling but some care is required when taking off again as it requires a gentle touch getting the revs above about 2000 before dialing in the throttle. As before the idle adjustment thumbscrew is pretty useless and I am wondering if this ‘fix’ has as much to do with cooler weather as much as anything else. Only real difference is the air screws out fron 2.5 to 4.4 turns and some tightening of a couple of loose diaphragm cover screws. What do others think?