Interesting belt problem.
 

Anyone have a belt lose 2 1/2 cogs before? I've never seen it before. they just ripped off a brand new gatorback belt. checked all the pulley's and installed the new belt and it did the same thing the original did. any ideas? :shock:

I'd eyeball all the pullies to check for alignment, spin them checking for wobble or grinding.

I've had a Gates belt toss a rib off before.

The Series 2 engine is notorious for killing plastic idler pulleys. VERY carefully check all of them.

went over the pulley's pretty carefully, I was starting to think maybe the idler pulley is alittle weak and it's backlashing?

Been there, done that. Ideler pulley disintegrated. Dang plastic.