i got a 86 250r motor. i saw a ad for a cylinder spacer plate. what does it actually do. do i have to modify anything else? thanks

 

It's not for you but they increase crankcase volume on 87',88' and 89' 250R's by raising the cylinder and using the taller 86' piston. Thats why you cant use it.As far as other mods(if you had an 87',88',or89) you just need the longer stud and dowel kit $20.Also you can't use your headstay that goes from your frame to the top of your head. Sorry but I saved you $60 bucks + shipping and handling.

88' 250R lots of extras

 

The spacer plate can be used with any year cylinder and any year crank. The rod has to be the 87-89 style which was 5mm longer than the 85/86 style. The piston has to be 86 style because the wrist pin location was moved 5mm to compensate for the longer rod.

The spacer plate set up increases case volume and smoothes out the powerband. You can also benefit by using the 86 style piston which had larger pockets on the sides.
ERIC