Did you actually need a wider crank? I built a Micargi Rover, and the crank arms cleared the motor with no problems.
You can probably just screw yours back together. I think you'll need a special tool for tightening the lock ring.
Is the crank you're using a 3 piece, with square tapers on the crank arms? If so you might be able to buy a sealed bottom bracket for about $10 and never have to worry about maintenance.