Need some tech help please. Both bikes Identical,...Reconfigured airboxes, 102 main jets, drilled needle seats, 19/27 sprokets, still running stock exhaust's. Here's the question....after removing the roller weights from bike 1 and step-drilling to remove 25% of weight from the rollers we have noticable gain in RPM's but seem to have lost bottom end. No other changes to tranny have been made. Clutches,clutch springs and torque spring all still stock. What did we miss?

 

My best guess is by lightening the rollers it has thrown you engagement timing off somehow. Why was you lightening hte rollers if it was ingageing right before that? I think you had ask me before what is inside that exhaust. I really was not sure so I took one and cut it. Inside you will findthe exhaust comes out of a cone smaller than the chamber but it does get big. Right after the cone about 1/2 inch is a solid plate. The exhaust is forced to turn and go back behind the first cone. There it goes into a silencer and runs under the solid plate and hits another solid plate. It travels up this solid plate until to reachs another silencer and goes thru it. Then it runs out the tail pipe that looks like a silencer thru a spark arrestor screen and out. It is made very similiar to a car muffler beleave it or not. we gutted that pipe and put it on but the gains was not as much as I thought they would be. A flat roller will have you pulling your hair out. Make sure they are good.

 

Was hoping you would be one of the first to answer Tommy. We have noticed a slight " LUL " or hesitation in the RPM range with tyhe stock rollers and after reading several post where others had either removed or used lighter rollers to let the RPM's reach higher before engaging the clutch we thought we would give it a try. Lined up going off a flagged hole shot start, the lighter roller 90 is showing a definitely stronger torque....or put this way, the front end rises dramatically more...., than the other 90 but loses almost a bike lenght within the first 5 feet and needs nearly 100 ft before it can make that 5 feet up. Should we be thinking stronger torque spring on rear pullys or maybe lighter clutch springs. As for exhaust, thank you for info, am assuming that you researched the DS 90 pipe and it would not benefit us to alter ours since your researched found very little increase in the power band.

If possible would like to speak to you 1 to 1.....will PM e-mail address.