TurboNova Posted April 26, 2011 Report Share Posted April 26, 2011 Thinking about buying a buddys 99 cr250 that needs the top end done. Never had a 2 stroke or messed around with a top end. Anyone on here a dirtbike guy that has done one? How difficult is it to do and what kind of time investment to do it. Recommend doing anything else while apart I was pretty much just going to buy a wiseco top end kit and install that Quote Link to comment Share on other sites More sharing options...
tl1kr Posted April 26, 2011 Report Share Posted April 26, 2011 It's pretty easy to do. Depends on why the top end needs rebuilt as to how long it would take and cost. A simple piston and ring replace should only take a couple hours. A guaged sleeve would need to be bored and honed to an oversized piston. The oversized piston would depend on how deep the scrapes are. An .010-.040 oversized piston shouldn't need any rejetting on the carb. Replace the wrist pin and bearing while your in there too. Hope this helps Quote Link to comment Share on other sites More sharing options...
TurboNova Posted April 26, 2011 Author Report Share Posted April 26, 2011 Yeah it runs, just got some low compression. Has enough hours for a top end to be done on it, but bike has been maintained and only trail riding. I notice Wiseco has pistons kits with a single ring and one ring? If the bike I get has the single ring can I get the dual ring and upgrade it... Quote Link to comment Share on other sites More sharing options...
AJ Posted April 26, 2011 Report Share Posted April 26, 2011 should take about an hour. very easy. do not use wiseco anything, unless something has changed in the last few years they are pretty common to lock up. as far as over size, they sometimes letter the over size i.e. A, B, C. A would be stock size, i always replaced them with the B pistons oversize. Quote Link to comment Share on other sites More sharing options...
TurboNova Posted April 26, 2011 Author Report Share Posted April 26, 2011 should take about an hour. very easy. do not use wiseco anything, unless something has changed in the last few years they are pretty common to lock up. as far as over size, they sometimes letter the over size i.e. A, B, C. A would be stock size, i always replaced them with the B pistons oversize. I can stay stock size as long as their are no gouges or scratches in bore right? and what top end kit do you recommend? Quote Link to comment Share on other sites More sharing options...
tl1kr Posted April 26, 2011 Report Share Posted April 26, 2011 I could be wrong, but I've never seen a piston with only 1 ring, always 2. Sounds like you would be good with a standard rebuild kit. I've used many differant brands and haven't had problems with any. Ironpony should have all the parts you would need in stock, so I would suggest taking it apart first just in case you run into something. Quote Link to comment Share on other sites More sharing options...
AJ Posted April 26, 2011 Report Share Posted April 26, 2011 can if you want to, i always ran one size over. you don't have to do anything other than put it in like stock. rings depend on the bike, my 250's were 1 ring. Quote Link to comment Share on other sites More sharing options...
TurboNova Posted April 26, 2011 Author Report Share Posted April 26, 2011 oh ok, whats the incentive of running one oversize on the piston then Quote Link to comment Share on other sites More sharing options...
AJ Posted April 26, 2011 Report Share Posted April 26, 2011 cylinder wear. little bigger piston to make up for the wear in the plating in the cylinder liner. Quote Link to comment Share on other sites More sharing options...
mjrsplat Posted April 26, 2011 Report Share Posted April 26, 2011 jugs are usually pretty easy to find and dirt cheap, depending on the bike. my cr always got a bored out jug when i did a rebuild. i was not at all nice to my bike though, race gas and running the fuck out of it for a million hours. mj usa on cleveland avenue is where i always went to get top end kits and have the boring done. assembly is easy too, like others have said, should take about an hour or two tops. Quote Link to comment Share on other sites More sharing options...
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