250R & trx250R

[Mr. Kind]

are the cylinders / heads from a TRX250R compatable with a 85 / 86 250R?

[Kaysen]

Yes all 85-89 cylinders and heads are interchangable... That being said, there are differences in each model. 85-86 engines were shortrod with a non-bridged intake. 87-89 were longrod with bridged intakes. The pistons change to accomodate the different rod. The 88-89 cylinder is regarded as being the best, the 87 generally the worst. Each year head has a different dome configuration and squish band setting for different burn characteristics, many prefer the 85-86 styles, especially if you are going to cut on it. My personal setup is an 85 cylinder, billet head (23cc dome), 86 trans and cases, 87 piston, 88 rod and 89 clutch. It runs very strong with a terrible port job...