motor crazy Posted June 3, 2010 Share Posted June 3, 2010 hi all. i have a problem with my dt. my boy was on it up the woods the other day. he came out of the woods,accelerated in first,missed a gear,so reved it in neutral before going in to second. when he took off,the bike started spluttering,and back fireing,and rattling like hell. there is no go in it. it was fine before he missed a gear. i have checked the timing,and that seems ok. when you try to start it, it back fires. it does run,but there is no go in it. it is making a loud rattling noise from the head. anyone have any idea what the problem is . cheers colin. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 4, 2010 Moderator Share Posted June 4, 2010 hi all. i have a problem with my dt. my boy was on it up the woods the other day. he came out of the woods,accelerated in first,missed a gear,so reved it in neutral before going in to second. when he took off,the bike started spluttering,and back fireing,and rattling like hell. there is no go in it. it was fine before he missed a gear. i have checked the timing,and that seems ok. when you try to start it, it back fires. it does run,but there is no go in it. it is making a loud rattling noise from the head. anyone have any idea what the problem is . cheers colin. Sounds like youve done the rings, when the engine is reved really hard with no load the piston sort of wobbles about in the bore as there is no load to centalise everything. In the extreme you can lose parts of the piston. You are going to have to take the barrel off and physically check inside, even money there is busted metal in there. Rings are favorite but a chunk off the piston at the exhaust port is not out of the question either. Link to comment Share on other sites More sharing options...
motor crazy Posted June 5, 2010 Author Share Posted June 5, 2010 Sounds like youve done the rings, when the engine is reved really hard with no load the piston sort of wobbles about in the bore as there is no load to centalise everything. In the extreme you can lose parts of the piston. You are going to have to take the barrel off and physically check inside, even money there is busted metal in there. Rings are favorite but a chunk off the piston at the exhaust port is not out of the question either. Link to comment Share on other sites More sharing options...
motor crazy Posted June 5, 2010 Author Share Posted June 5, 2010 Sounds like youve done the rings, when the engine is reved really hard with no load the piston sort of wobbles about in the bore as there is no load to centalise everything. In the extreme you can lose parts of the piston. You are going to have to take the barrel off and physically check inside, even money there is busted metal in there. Rings are favorite but a chunk off the piston at the exhaust port is not out of the question either. hi cynic. took the piston out today. there is a large piece missing off the bottom of the piston,and there is some impact damage on top of the piston,which has squashed the top ring solid. the barrel,and head are ok. how do i know what size piston to order for it. cheers colin. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 6, 2010 Moderator Share Posted June 6, 2010 hi cynic. took the piston out today. there is a large piece missing off the bottom of the piston,and there is some impact damage on top of the piston,which has squashed the top ring solid. the barrel,and head are ok. how do i know what size piston to order for it. cheers colin. You need to clean the carbon of the top of the piston, take it steady with a wire brush or similar and you should see some numbers stamped in the top if it had been bored which is more than likely with a stroker. generally it runs at .25, .50 and .75 above that you will most likely be into patern parts but some of the manufacturers go to 2.0mm So once you have cleaned the piston up so its nice and shiny you will see any numbers that will be there, generally they are towards the exhaust port. Then you will be able to order a piston at ## oversize. Link to comment Share on other sites More sharing options...
motor crazy Posted June 6, 2010 Author Share Posted June 6, 2010 You need to clean the carbon of the top of the piston, take it steady with a wire brush or similar and you should see some numbers stamped in the top if it had been bored which is more than likely with a stroker. generally it runs at .25, .50 and .75 above that you will most likely be into patern parts but some of the manufacturers go to 2.0mm So once you have cleaned the piston up so its nice and shiny you will see any numbers that will be there, generally they are towards the exhaust port. Then you will be able to order a piston at ## oversize. i cleaned the piston,but it is to badly damaged to see any numbers. i will have to get it measured,or take it to a shop to get one the same. cheers colin. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 6, 2010 Moderator Share Posted June 6, 2010 mmm piston...power valve...another collision??? The damage, is it at the exhaust port part of the piston? Link to comment Share on other sites More sharing options...
motor crazy Posted June 6, 2010 Author Share Posted June 6, 2010 mmm piston...power valve...another collision??? The damage, is it at the exhaust port part of the piston? hi. yes there is a large piece broke off the bottom of the piston,and some impact damage on the top,on the exhaust side. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 6, 2010 Moderator Share Posted June 6, 2010 hi. yes there is a large piece broke off the bottom of the piston,and some impact damage on the top,on the exhaust side. you might want to read this, its not the only case I have seen on forums either. Link to comment Share on other sites More sharing options...
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