joandemma Posted July 1, 2007 Report Share Posted July 1, 2007 I have an 02 txt edition 280 gas gas, which has an annoying noise which sounds a bit like knocking- I get this noise when backing off throtte and not when on power. Bike runs fine apart from noise.I fitted new piston rings but this did not solve the problem, checked bearings for movement up and down and they were ok (big end and little end). Could it be that the actual piston is worn? Bore of cylinder looked fine with no step to indicate any wear. Please help, cannot afford to take it to bike shop for fix. Quote Link to comment Share on other sites More sharing options...
ridgrunr Posted July 1, 2007 Report Share Posted July 1, 2007 (edited) I have an 02 txt edition 280 gas gas, which has an annoying noise which sounds a bit like knocking- I get this noise when backing off throtte and not when on power. Bike runs fine apart from noise.I fitted new piston rings but this did not solve the problem, checked bearings for movement up and down and they were ok (big end and little end). Could it be that the actual piston is worn? Bore of cylinder looked fine with no step to indicate any wear. Please help, cannot afford to take it to bike shop for fix. My 321 and 280 both did the same thing. Made me crazy for awhile, put in new pistons, rings, checked bearings, clutch, nothing seemed to make it better. Then I started checking around and found that most Gassers make that noise to some extent. Some more than others, but mine was a 99 321 and a '00 280 and we rode them for ten years like that. The guys I sold them to is still competing on 'em. So I'd quit fretting, just ride it and enjoy. Edited July 1, 2007 by Ridgrunr Quote Link to comment Share on other sites More sharing options...
coxy Posted July 1, 2007 Report Share Posted July 1, 2007 what grade petrol are you using as this could be the reason for this knocking noise when backing off the throttle, try and get as high grade petrol or as close to 100 as you can and this should quiten it down abit but maybe not get rid of it totally Quote Link to comment Share on other sites More sharing options...
joandemma Posted July 1, 2007 Author Report Share Posted July 1, 2007 Cheers guys, will try different petrol to see if it sounds different. Quote Link to comment Share on other sites More sharing options...
peterb Posted July 1, 2007 Report Share Posted July 1, 2007 From reading the text, it would sound like the motor is pinging, usually due to a lean mixture. You should have a D36 needle, with the clip second notch off the bottom, pilot screw out approx 3.5 to 4 turns, about 115 main jet. I usually run pump petrol at 95 octane with a 50:1 fuel/oil ratio using mineral 2T oil. Never had a pinging problem. Bye, PeterB. Quote Link to comment Share on other sites More sharing options...
motojojo Posted July 2, 2007 Report Share Posted July 2, 2007 It depends on were you live if you live at a high altitude your octane don't mean much but down low pump gas will ping when you back off the throttle. Quote Link to comment Share on other sites More sharing options...
peterb Posted July 3, 2007 Report Share Posted July 3, 2007 Thanks GT, We live close to sea level, haven't much chance to experience high altitude trials. Bye, PeterB. Quote Link to comment Share on other sites More sharing options...
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