Melex 512E has no power

[deadeye1]

I have a 1982 Melex 512E. I have replaced the batt, upgraded the cables to
4 gauge welding cable with all new copper lugs crimped & soldered. Replaced
the solenoid. Removed and disassembled the motor cleaned with compressed
air and checked the brushes, they look fine. My Wife and Myself and the dog
go for rides and the cart lacks power on a small grade. My speed seems to be
ok I just need more power.

My friend has a 1996 ez-go with new batt. his cables look like crap. Him, his
Wife and 2 other people can ride that cart almost anywhere they want to go
with no lack of power. My buddy weights about 280# and his wife 170#.

Any suggestion on what I need to do next to get this cart to go.

These are 36 volt carts. Thanks for any help