monkster Posted February 27, 2017 Report Share Posted February 27, 2017 i have a 2001 gas gas 250 idling problem when i start bike and give it a rev and let go the revs seem to be staying up ive tried a different carburetor and reed valve seems ok the fuel mixture is 80/5 and when the bike is warm and i turn it off and go to start again it wont start unless i put the choke on ive changed the plug 3 time to the factory one (NGK BPR5ES) all help appreciated Quote Link to comment Share on other sites More sharing options...
lineaway Posted February 28, 2017 Report Share Posted February 28, 2017 Pull the flywheel cover off and give it a good tug up and down. Good chance the mains and seals have gone bad, 1 Quote Link to comment Share on other sites More sharing options...
monkster Posted February 28, 2017 Author Report Share Posted February 28, 2017 That's my next plan I'm waiting on a flywheel remove tool coming to check it. Are u able to adjust the timing on them just incase the person I bought it of was messing around with timing thanks Quote Link to comment Share on other sites More sharing options...
lineaway Posted February 28, 2017 Report Share Posted February 28, 2017 To check the mains you do not need to remove the flywheel. You are checking movement. Quote Link to comment Share on other sites More sharing options...
monkster Posted February 28, 2017 Author Report Share Posted February 28, 2017 ok thanks will do that tonight and let you no but it seems like its sucking in air from somwhere so ill check the crank seal when the tool comes Quote Link to comment Share on other sites More sharing options...
lineaway Posted February 28, 2017 Report Share Posted February 28, 2017 If the mains are moving, so is the seal. Bingo, that is the air leak. Quote Link to comment Share on other sites More sharing options...
pauls320 Posted March 1, 2017 Report Share Posted March 1, 2017 Keep in mind you can still have a ''Bad'' main seal even if crank shows no visible slop... Quote Link to comment Share on other sites More sharing options...
monkster Posted March 1, 2017 Author Report Share Posted March 1, 2017 sorry only getting to reply now but ive re jetted the carb checked reed vavle cyclinder compression checked the timing and replaced the reed valve rubber and the bike is a bit better but its now missing/back firing any help? Quote Link to comment Share on other sites More sharing options...
b40rt Posted March 1, 2017 Report Share Posted March 1, 2017 Why re-jet ? Quote Link to comment Share on other sites More sharing options...
monkster Posted March 1, 2017 Author Report Share Posted March 1, 2017 just so i no it was jetting and carb was working properly Quote Link to comment Share on other sites More sharing options...
monkster Posted March 1, 2017 Author Report Share Posted March 1, 2017 im just wondering would the voltage regulator module or this we thing in picture cause this or cdi unit? Quote Link to comment Share on other sites More sharing options...
b40rt Posted March 1, 2017 Report Share Posted March 1, 2017 45 minutes ago, monkster said: just so i no it was jetting and carb was working properly Not trying to be a smart ass, but where did you get your "proper" jetting figures from ? Quote Link to comment Share on other sites More sharing options...
monkster Posted March 1, 2017 Author Report Share Posted March 1, 2017 i got the proper jetting from gas gas uk " the ones they said they use on the bike from factory" and theres no play in bearing "pulling flywheel up and down" and tested seals by pressurising the hole engine Quote Link to comment Share on other sites More sharing options...
dadof2 Posted March 2, 2017 Report Share Posted March 2, 2017 Pressurising the engine does not necessarily prove the seals are OK. The seals are designed to seal tighter with crankcase pressure. It is when the crankcase is at negative (relative to atmospheric) pressure that worn seals allow air in. You would have to create a vacuum of at least 22 inch mercury to assesses the seal effectiveness. 1 Quote Link to comment Share on other sites More sharing options...
faussy Posted March 2, 2017 Report Share Posted March 2, 2017 (edited) And how did you pressurise the engine, im intrigued 5-10 inches of mercury would be more than sufficient btw Edited March 2, 2017 by faussy Quote Link to comment Share on other sites More sharing options...
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