[Big Bore Crankshaft] - ATV Riders Forums - Honda, Yamaha, Suzuki, Kawasaki, Polaris, CanAm, Arctic Cat, Kymco ATVs

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Big Bore Crankshaft
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Posted by: Duke450r

Hey guys, I wanted to get some input on my project.

I have a 88 trx250r, right now I am gathering parts to completely rebuild the engine from the cases up. I have decided on a 330 big bore.

I am going to buy a new crankshaft to go in the engine and I would like some input on whether I should go with a short rod 86 style or the long rod 88 style crank. I realize that you can use either rod with the inclusion of a spacer plate on the 88. I just wonder which rod style people prefer.

Thanks
G.D.

Posted by: Dave83

I like the long rod/spacer plate setup.It seems to help the bottom end "pull" some.What kind of riding you do?The smoothest R I have ridden was a 370 stroker with ESRs top end porting.The stroker really smoothed out the powerband.

Posted by: tx_250r

i think hot rod has a +4mm stroker crank for like $250 i wanted it but didn't want to have to deal with replacing the crank.

Posted by: 440ex dragger

I am running a spacerplate and 88 crank on my 330R, runs great. I TT race and it runs circles around most other bikes on the track.

Posted by: Duke450r

Thanks for the replies, I suppose that theoretically the short rod is suppose to rev faster. But I have always heard that the 88-89 were a little better engines. Possibly because of the bridge on the intake in the cylinder. Which doesn't matter when you put in the big bore.

Thanks
G.D.

Posted by: Eddiesanders250

i would go with the 87-89 style crank. It all depends who you ask, some people on here are short rod fans, some are long rod fans.