'87 250R Engine question

[mundenbk]

Hi all,

Got a question for ya all. I just bought an 87 and it appears to have a spacer plate between the jug and base. I have not seen this on any other engine before, is this stock or aftermarket? The only reason I can see it being in there is to lower compression? or longer rod. Are my assumptions correct or should I just rip it apart and start taking measurements. The guy I got it from said it was bored 30 over but never said anything about the spacer.

Any help would be appreciated,

Brian

[joe22883]

It probably has a longer rod. I just ran into a problem with my R when i ddi the top end (technically not a problem) i found out it had a longer rod in it and i ordered an 86 piston and the 86 piston is taller then the 87-89 so i installed a spacer plate. From what i got it is a better set up anyway.

[mundenbk]

I will keep this in mind when it needs a rebuild. I might just pull it apart anyway, kind of a restoral process, and polish the jug and head. Can you buy just longer bolts for the cases. It looks like the ones that are on there are a tad on the short side. Also what was the stock swingarm made out of. Mine is powder coated but thinking of polishing it.

Thanks

Brian

[joe22883]

Well if it has a spacer plate longer studs should have been installed i dont think it would work without them but i coud be wrong.If it never had teh longer studs insatlled id suggest getting them but again i dont believe the stock studs would be even close enough to fit the spacer plate. ESR makes the spacer plate so does nacs i ordered mine from esr they had them in stock and very good prices so id suggest checking them out.As far as the swing arm goes im not really sure i know if it has been pwoder coated it will be tuff removing it but maybe sandblastin it would do the trick so of the guys on here would know better then me about stripping it down to polish it.

[team22]

your getting wrong advise. what you have is a 86 cylinder on a 88 89 style bottom end it's not a bad thing cause you can go bigger bore on the older cylinder 86 goes up tp 273cc 88 89 goes only to 265cc.

[robyone]

The reason for the spacer plate, is that you have a long rod crank (88 89 ) and a 86 piston. (all year jugs are interchangable)
There is a 5mm difference in wrist pin locations between the 85 86 pistons and the 88 89 pistons. So if you have a long rod crank, and want to run a 86 piston for the larger bore sizes ( 85 86 pistons sizes go up to 69.5 and the 88 89 sizes only go to 68mm) you need to use a spacer plate to make up the 5mm difference.
The spacer plate also adds more crank case volume, which makes for better bottom end power.