I just finished my 1986 TRX250R. When I got it the sprocket side of the case had some damage from the chain popping off. So I rode it for a month and then the piston cracked and the sleeve got damaged. So I split the case and checked the whole bottom end out. The water pump was bad also, so I replaced the whole water pump and gaskets. Bought a brand new left side case, and bolted it all back up. So that took care of the bottom end, and now on to the top end. The crank was all good (recently replaced by old owner), So then one of my friends had a 1989 CR250R Paul Turner Racing cylinder convert for a TRX250R so I bought it from him and then ordered a Wiseco top end kit for it. I just got it all together and it is running great. I know it isn't a Raptor but it was a beast in its day and still a legend.Sorry for the long post just excited.
Super long shot..... Looking for this EXACT cylinder for a ATC250R build I am embarking on. Had one of these in the late 80's that I used on an ATC250R for the Nationals/Mickey Thompson races.
If anyone can help me find this bike/cylinder will be highly indebted!