I'm wondering which one is faster. The 85-86 Lt 250r have a gray engine and the 87 and up have blue engines but the reed valve systeme is very different. Thanks.

 

87 is faster

 

There are a few differences actually. The swingarms are different, the engines as you noted are different as well. The '87 came with a power valve and the different reeds. In '88 I believe the power valve changed again to a slightly better one. The '85-86's had a 5 speed tranny vice a 6 speed in the '87 and ups. The rear shock may be different too, I've read in a few places that they ('87 and newer) had Showa rear shocks but my '86 LT has a KYB rear shock (which seems very nice to me). '87-'92's also had a different seat, though any of the seats fit any of the plastics which are the same on all of them. The rear tire and rim sizes were a little bit different as well.

 

Don't even compare the two, the 87 is all over the 85-86, as you will find out the resale prices will reflect. There are so many LT250R's out there now, don't even think about the 85-86. Not only is the motor far superior but its wider, the frame is stronger, the front shocks are better (not great though). The power valve is the same on all 87-92 lt250's, its the reed cage that is different on the 87, its reed cage is 1/3 bigger than the 88-92. I have a 92 with an 87 cylinder on it.