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'* and installed the new belt and it did the same thing the original did. any ideas?

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

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