Well shes thrown a hissy fit yet again

All has beennfine since fitting a new motor a few months back but upon turning the lathe on it tripped the main breaker for the garage,after doing this a few times in a rowci admitted there was a problem.
I checked the motor brushes and gave them a quick clean, re fitted and the lathe ran in forwords fine
I stopped the lathe switched to reverse and when setting her off pop goes the breaker again

So I re set thinking ill just make do without reverse this time, only now it trips in forward or reverse!
Anyone have any ideas this time?