only new belts ive broken are aftermarket belts i didnt put through a break in cycle. all belts should go through a break in cycle before wide open running.
Is the driven sheave actually moving. Some kawa's had a problem where the secondary was not opening and causing the belt to cock sideways, may need to run without the cover on and watch. Any burnt rubber smell?
since you have not answered some of the ??. since your first belt blew, you may have a roller out of place, causing this. take the primary off and inspect and regrease it. install a new yami belt.
since you have not answered some of the ??. since your first belt blew, you may have a roller out of place, causing this. take the primary off and inspect and regrease it. install a new yami belt.