Adz82 Posted February 9, 2016 Share Posted February 9, 2016 First off hello everyone new to the forum got a problem with my sons 2000 model dtr125 here goes noticed a lot of blowby on standard piston when fitting a dep pipe, whipped the top end off and sent to pjme for a rebore new piston and a shave of the power valve as its now going to be 2.00 oversize got the parts back checked the ring end gaps etc all bang on put it together checked its turning free then tried to start it and 6 kicks later very erratic idles like the slide is stuck slightly open then tried to stall then Rev up again, I killed the bike took the plug out turned the kickstart quite hard and notice a metal to metal knock now the piston box is marked tzr125/250 me thinking pjme obviously know it will fit else they would not of supplied it I'm about to tear the bike down and check the deck height but thought I would post here incase anyone else had any ideas I'm thinking wrong piston maybe slightly taller but surely they wouldn't of made a mistake like that ?? I'm gonna give em a call after I check the deck height Link to comment Share on other sites More sharing options...
Moderator Cynic Posted February 9, 2016 Moderator Share Posted February 9, 2016 You need to tear it down to find the problem, the tzr 125 piston is a little disconcerting, I thought they were slightly different sizes. Depends on year/model etc though. Link to comment Share on other sites More sharing options...
Adz82 Posted February 9, 2016 Author Share Posted February 9, 2016 Hi cynic just been into the top end and seems as though the piston is hitting the centre metal band of the Athena head gasket,pjme advised us to grind it away for bigger clearance so the piston would not touch it and done that bolted it back up and she went first kick and is running great. So anyone having similar when running a 2mm oversize piston check that head gasket 1 Link to comment Share on other sites More sharing options...
blackhat250 Posted February 9, 2016 Share Posted February 9, 2016 Check the wrist pin height, against the old piston Link to comment Share on other sites More sharing options...
Moderator Cynic Posted February 9, 2016 Moderator Share Posted February 9, 2016 Glad it was simple, did they not tell you this when you picked up the parts? Link to comment Share on other sites More sharing options...
Simon46 Posted February 9, 2016 Share Posted February 9, 2016 Been on grampian motors Liverpool who sell mitaka pistons. If your going too far oversized for they recommend a yzr piston. Looks same dome height etc. Link to comment Share on other sites More sharing options...
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