91 marathon moves one time the next nothing

[merrittjosh]

I have a 91 Ezgp Marathon 36v series cart. I recently stripped the shaft on stock motor ( 22 inch tires backseat added and hilly) I replaced the motor with a D& D
Model 170-002-0001 high torque motor and a 500 amp Chinese knock off controller. When I press the gas pedal it may move and second later it will not move. I’ve done every test I can find and think it’s the pot but I’m not sure
It tested at 6200 ohms and I’ve read that anything over 5800 is bad but I also read somewhere that 6200 was ok and it’s the only thing that hasn’t been replaced since I got the cart last year.
Bought new resistor and it tests good in neutral but not in forward it drops about 6v
If you check voltage on f&r in f it reads pack voltage at A it will read 13-14 volt on b . Any help in the right direction would be greatly appreciated!