250 R cylinder

[BWard]

Will a 1986 atc 250R cylinder bolt right up and work on a 1985 atc 250R ?
Thanks,
Brian

[smokinwrench]

Yes it will all cylinders are the same.

Make sure you buy the correct piston, they have short rod and long rod pistons.

[factoryX]

since this thread was made, what about a 87-89 top with the 87-89 piston but on a 85-86 short rod? or do you have to have the long rod?

[whyzee]

Buying a brand new 2009 crf450r - $6000
I am a Honda man all the way, but the 2009 and 2010 crf450's are not a well handling bike. Go with a KXF250! you don't need a 450, trust me ! open expert class

[smokinwrench]

Factoryx- You can run a long rod bottom end with a short rod piston, you have to run a spacer plate between jug and case also have to have long studs. Anytime you go to a big bore you have to run this setup because all big bore pistons are built as short rod pistons. 87-89 pistons also only go up to .090 over I think but 85-86 pistons go up to .140 so you can get a few more bores. I don't think you can run a short rod with long rod piston. Only difference between pistons is wrist pin location.

I think all of this started years ago because supposidly the long rod has a smoother power band and the short rod has a much harsher power band hit. I have read many places short rod for drag racing and long rod for mx. I have owned a couple of each and I don't think it makes a difference. Running long rod bottom end with short rod piston and having the spacer is supposed to give more intake area in bottom end and give more power I think they are full of it. Me personally I wish they made long rod pistons in the big bore because I don't like the spacer plate, just another spot for a leak.

Whyzee just letting you know you replied to his signature.

[factoryX]

thanks for clearing that up for me, kind of sucks because all of the aftermarket heads are 87-89 long rods.. my sig was kind of a joke but thanks for the info. Yes kawi and yamaha right now are the best in the business, even yamaha 2 stroke are faster than ktm.

[JohnR.]

kind of sucks because all of the aftermarket heads are 87-89 long rods..

The rod length has no bearing on the head. Besides the facts mentioned above a longer rod motor will have less severe rod angles thus making for a more reliable engine. I'm sure if you do a search on google or yahoo about rod length in internal combustion engines there will be a ton of info. 99.9% of the stuff that relates to 4 stroke engines (be it multiple cylinder cars, street bikes, or single cylinder types) holds true for two strokes as well. For me, the main reason to go with the long rod is the rod angle being reduced. I would have thought that by now there would be aftermarket cylinders with the extra material on the base so that you don't need to run a spacer.

John