Rear diff pulley wrecked after 1st run on Mi4LP

[stnorm]

Ive just built my Mi4lp and was really looking forward to seeing how she went. Alas after a couple of mins it felt like i had no rear wheel drive and after inspection the belt had melted both fences off the diff pulley and fell off. New diff pulley and fences ordered but any ideas why this might have happened. im using a Norsram rure 10.5t motor with a 21t pinion onto the stock spur gear powered by bionic's 4000mah, 40c lipos. Im new to belt drive cars so could it be the belt tension that is at fault? The rear belt has about 3mm up/down play in it. Should I take the shims out of the diff pulley to allow more free play? Any advice would be much appreaciated

[DCM]

erm, belt sounds a little tight, but did you bed the diff in, did you check fot slippage after a couple of laps??

[stnorm]

I wasnt going flat out with it but what do you mean by bed the diff in sir? Car is crazy fast, even at 50% throttle.

[bigred5765]

or u may have had the pulley tensioner set differently to each other

[MattW]

Only thing I can think of is if you had the pully the wrong way round so that the belt didn't line up correctly.

We can usually go for a number of meetings without touching the diff - and I haven't even killed a diff pully - in a number of years!! One of the pullies that I am still using on one oy my diffs is actually a number of years old.

[stnorm]

think I realise what i did. Dont think I snapped one of the fences on properly and it must have partially come off the pulley. have double and triple checked the new one and all seems ok now. Cheers for advice everyone