Yamaha mountain sled specialist Tom Hartman works with modified Yamaha mountain sleds on a daily basis. He tells his customers to replace the very durable yet very hard OEM 8DN drive belt with a Dayco Ultimax 3 instead (#138-4432-U3).
The stock 8DN belt is very durable, but being so hard there is a fair amount of slipping, which creates heat and a loss of acceleration. This Dayco belt is a softer compound so there is less slipping and less heat, and it is slightly longer, making it easier to get a full ratio shift out (allows you to get the drive belt ride height in the secondary to the top of the sheaves while maintaining proper deflection.)
Hartman also echos the recommendations to properly break-in every brand-new drive belt for 30-40 â€œeasyâ€ miles where the belt isn’t subjected to excessive loads that will create excessive heat. Therefore, break in your new drive belts at a convenient time and place – before you’re way out in the backcountry and need it to work right NOW!
Hartman also suggests periodic cleaning of the drive belts – wash it in hot water and soap, a grease-cutter like 409 or Simple Green. Use a brush (not too stiff or aggressively) to scrub the belt sides clean (grip surfaces). Let dry overnight. This will keep the belt grip surfaces clean and there will be less slip and more grip (assuming the clutch sheaves are cleaned as well). This means less slip, less heat, more acceleration and the belts will last longer – much longer.