In 1997 pro circuit put a 14 tooth counter sprocket the the rm250 while the PC cr, kx, and yz all had a 13, why did they do that? however i dont know the rear sprocket size for 97. and in 1999 the RM250 modified by PC got 14/52 gearing, why? whats with the 14 tooth counter sprocket ? is there an advantage?

maybe the 14T complimented that bikes torque curve. Tim Ferry used a 3 speed transmission in early 2000's

Has something to do with chain binding or torque and it's effect the suspension. You can still get the same gear ratio or very close. You might have to modify the chain guide with the larger rear sprocket. I think MXA did an article on this a few years back.

Personally I always thought that they did it because RM's always had a light crank and a small flywheel, which tends to make the rear tire spin out of control when there's a lack of traction.  A bigger front sprocket (or smaller rear) will make it easier to control, today we would just add a flywheel weight (or do both!).

I don't know about it's effect on the rear suspension, so that's totally possible too.

Smaller front sprockets wear chains faster, especially when geometry angles come to play. They obviously feel that the angles on RM's benifit from larger sprockets. I personally have found sometimes running a different sprocket combo for the same ratio makes it possible for the rear wheel to be in the position desired in the swing arm keeping your wheelbase where you want it to be. I run a 14-48 gear ratio on my RM for off road and 14-52 for moto and it SEEMS to unload the suspension better on square edge chop(not so harsh feeling). It could be a mindscrew or the real deal, I dont know.

wow, theres a lot of possiblities as to why. ...

SMarquez, on 31 August 2012 - 03:27 PM, said:

do you still have the article?

bigdaddykane93, on 08 September 2012 - 08:30 AM, said:

No, I don't. I was just trying to recall something from a few years back. It was something that started in Supercross and MXA checked it out. You can go to the Renthal site and they should have a gear ratio chart to show how it works, then you can try it out and see if it affects suspension action.

Edited by SMarquez, 09 September 2012 - 08:54 AM.