Belts Breaking and High RPMS

[rummel]

Hey need some advice or pointers on what to do. We currently have a 90cc drr with a chriss grissom head and cylinder liquid cooled. We usually run mx but now were trying a little ice racing in alaska and were only going to be stationed there for six more months so i dont want to spend alot of money setting the bike up for flat track racing. Last year we broke at least one belt at every race and he has the stage 6 rpm gauge the bike was running over 12000rpm and im assuming thats why we were breaking belts because we have never broken a belt running mx. Any ideas on how to town down the rpms so that we dont break a belt at a reasonable price.

[Rich243]

We were breaking belts a couple years ago when we started getting the rpms up higher and it was an alignment problem. If the front and rear sheaves are out of alignment even slightly, it generates heat....the more rpms the more heat and belts break. Once we fixed the alignment problem, the belts were fine.

Good luck!!

[rummel]

how do you effectively measure the belt to make sure its aligned right. I know that i removed all the gears and parts that were used for the electric start and just cut my own spacer to put between the variator and case. im sure that has something to do with it cause i didnt use a micrometer and just winged it. hey what can i say im military we improvise haha

[Rich243]

I would call one of the Drr dealers and see if they can give you the exact spec. I was missing a very thin spacer and it was causing the belt breaks. Those sheaves have to be aligned just right to run the higher rpms.

[EthansDad]

I think the simple and cheap answer is add more gearing (taller). the higher rpms run the belt up higher on the variator and that can cause excessive wear. since you've gone from mx to flat track, you might try dropping the rear sprocket a few teeth. that WILL lower the rpms on top end AND lower the belt travel, and hopefully give you more top end speed.

I'm not a flat track guy, but if I was setting up our mx bikes to run flat track for 6 months, that's what I'd do.

-EA

[selbygirl]

sometimes you can look at the variator or rear pully for wear marks, after a burnt belt or use a dry arase marker .and mark both sides of the variator with the marker . and run it a few feet to see if you belt travels true.. and most hardware stores sells spacers and washers .. but most likely its your gearing change your sprockets to a higher gear, thats like flooring the gas in 1st gear for a long time. that will make for a lot of heat,,plus with the cold weather up ther going from a hard stiff belt at the start