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Old 11-05-2013, 07:31 PM   #5 (permalink)
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Trust me, fourth gear is just too tall for the output of this motor. Hit a headwind or any kind of hill and your speed and RPM starts dropping like a rock. The aftermarket has already responded to this problem, too--Yuminashi makes a lower 4th gear that helps a bunch. The problem is who wants to split the cases on a brand new bike to install it???

What the motor needs is a 5th or 6th gear and I sincerely doubt we'll ever see that.

Several guys are making their Groms hit the redline in fourth and increasing their top speed by dropping to a 14 or even 13 tooth countershaft sprocket. The problem there is it shortens up the other ratios as well. I bought a 14t. and the gizmo to correct your speedo since it's driven off the countershaft but after getting over 120 MPG decided to just leave well enough alone.

Installing a 150cc kit supposedly gives you enough power to pull fourth gear to redline but honestly I spent enough time and money building XR/CRF-50's for backyard adult pit bike racing (there's a stupid expensive one in the garage as I write this that I'll never get any money back out of) and nowadays all I want to do is just ride 'em.

Doing something about the wind drag would really help--and that's where you guys come in. Starting with a bike that already gets fantastic gas mileage puts you way ahead of the game. It's cheap enough that you wouldn't mind cutting it up especially once enough of them get into the used bike market and their prices drop.

Last edited by woodsrat; 11-05-2013 at 07:38 PM..
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