Before I installed the 25 tooth front pulley , I would pull the front wheel off the ground on a regular basis . The Belt never complained a bit and I've got almost 50,000 miles on it now. That larger front pulley makes 5th gear seem like "Over-drive"
but that was the end of the wheelies
.
You understand that when the swing-arm is completely parallel with the ground --- that is when the belt is tightest . As the shocks come close to bottoming out the swing arm is above center and the belt starts getting looser again ...
Hay , have you got extra long shocks on your bike ?
If so : you should know to adjust your belt when the swing arm is level and the length between the front pulley and the back pulley is at its longest.
You might be surprised to know the same problem occurs with chain drive too . That is why long travel dirt bikes have spring loaded chain tension arms on the bottom side of the chains.
Let us know how it works out for ya .
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The only time I adjust my belt is when I've had things apart putting a new tire on , then its good till the tire goes bald (8-10K-miles) ! You'll never get that kind of performance with a chain !