GZ250 Smokes on cold start, stops smoking after running

DBG · 02-27-2012, 01:50 AM

My bike spews blue/white smoke every time i start it after letting it sit a while. After a few minutes, the smoking stops and it purrs like a kitten. I've done some research on the issue, and it looks like it might be a sticking valve or worn valve seals causing oil to drain into the cylinder after i kill the engine. Then upon start up the oil that drained into the cylinder burns off in a cloud of ninja smoke. I ordered some new valve seals and plan on replacing them later this week. I'm also going to soak the entire cylinder head, inner block, etc., in Seafoam to get rid of any excess carbon. If this doesn't fix it, I'll move on to checking the cylinder walls and piston fit, etc. (engine has good compression already). If anybody has any suggestions, send em my way. I plan on posting the results once all is said and done.

wacio · 07-19-2016, 12:39 AM

First make sure choke is turned all the way off. It may be causing mix too rich on warm bike.

There is idle adjustment screw on the right sire of the carb (plastic knob). I need to tinker with it (about half turn) depending how hot the bike is. This bike likes high idle (about 1400rpm). If adjusted too low it may stall when coming to a stop from cruising speed (engine little cooler).

My philosophy on the carbs in bikes that sat for a while is to try to run them for two or three tank fulls. Often the little varnish in the carb will eventually clear up. Prior to taking carbs apart, watch few videos on youtube made by Shane Conley about carb cleaning to avoid common mistakes. Parts for carbs are not cheap and easy to screw up. I bought mine in april and it runs much better now (after 400 miles). I still hesitate to take carb apart - my problem is very small leak causing carb to be little moist on the lower half. I bought rebuild kit that has all seals needed to rebuild and float needle valve (although opinions on the aftermarket kits and esp valve are mixed). Will eventually get it done if it doesnt stop by itself. Best luck.

02-27-2012, 01:50 AM	#1
DBG Junior Member Join Date: Feb 2012 Location: Galveston Posts: 19	GZ250 Smokes on cold start, stops smoking after running My bike spews blue/white smoke every time i start it after letting it sit a while. After a few minutes, the smoking stops and it purrs like a kitten. I've done some research on the issue, and it looks like it might be a sticking valve or worn valve seals causing oil to drain into the cylinder after i kill the engine. Then upon start up the oil that drained into the cylinder burns off in a cloud of ninja smoke. I ordered some new valve seals and plan on replacing them later this week. I'm also going to soak the entire cylinder head, inner block, etc., in Seafoam to get rid of any excess carbon. If this doesn't fix it, I'll move on to checking the cylinder walls and piston fit, etc. (engine has good compression already). If anybody has any suggestions, send em my way. I plan on posting the results once all is said and done. Login or Register to Remove Ads
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07-19-2016, 12:39 AM	#2
wacio Senior Member Join Date: Apr 2016 Location: Illinois Posts: 174	First make sure choke is turned all the way off. It may be causing mix too rich on warm bike. There is idle adjustment screw on the right sire of the carb (plastic knob). I need to tinker with it (about half turn) depending how hot the bike is. This bike likes high idle (about 1400rpm). If adjusted too low it may stall when coming to a stop from cruising speed (engine little cooler). My philosophy on the carbs in bikes that sat for a while is to try to run them for two or three tank fulls. Often the little varnish in the carb will eventually clear up. Prior to taking carbs apart, watch few videos on youtube made by Shane Conley about carb cleaning to avoid common mistakes. Parts for carbs are not cheap and easy to screw up. I bought mine in april and it runs much better now (after 400 miles). I still hesitate to take carb apart - my problem is very small leak causing carb to be little moist on the lower half. I bought rebuild kit that has all seals needed to rebuild and float needle valve (although opinions on the aftermarket kits and esp valve are mixed). Will eventually get it done if it doesnt stop by itself. Best luck.
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