piston seized??99 cr250r

[Wavehog33]

You jacked up the cylinder. It should be fixed by replating. If it is an older bike that you are not really planning to maintain, ie. air filter cleaned after each ride, regular oil changes etc., then throw it back together with new piston, lick your wounds and sell it to someone you don't know. If you this is a nice bike that you will maintain properly, then fix it correcty!!!! Either way you are slightly screwed...sorry for the brunt honesty

[doodman]

Wow, that gouge looks nasty.

The big bolt is the powervalve check window, the slotted thing inside should turn at high revs, the boxxy cover is the actual powervalve assembly cover.

[2bitsamile]

email photos to replating shops and ask them how much to fix. They repair by welding to fill in gouge, boring, nikasil replating, and diamond hone to finished size. It's as good as new for much less $$

[mken]

just a quick update.ive decided to send the cylinder and head to a tuner in england,stan stevens.ive sent it over complete and he will send it away to be welded and plated and then tune(port&polish)the head.all this for bout 300 pounds n it saved me havin to take out studs and pulling apart the powervalve so all i gotta do is flush out the bottom end and reasemble.has any one used a Namuru piston and do all piston have to be drilled to lube the exhaust bridge.

[DoctorRzed]

You are best to go with a forged piston such as Wiseco.

Wiseco has been around for many years and trusted in race engines.

[2bitsamile]

+1 on forged piston like Wiseco, never have to worry about piston shattering. Wossner also makes forged pistons. Search for "wiseco" and you'll find many folks also recommend forged. If you buy piston +rings and send to the cylinder shop, they will size cylinder to the right clearance (0.0015" min for Wiseco) and check/set ring end gap.

any piston should have holes, if there is an exhaust bridge

Good idea to set piston to head squish, search "squish" for more details. I like a tight squish of 0.035".