[Mastiff]

belts for blades and tranny have pedal/arm release features that will release tension allowing motor to spin and that will slowly engage/disengage drive and blade components preventing wheelie. I.C.E. was 5000 r.p.m. Electric is 4000. R.P.M. and it is a series wound.

You can NEVER, NEVER remove the load from a Series wound Electric motor.

If your running the Series wound motor and you let the load off of the motor it will spin up to 10,000+RPM and literally Arc and explode.
This will happen even with a controller.

You simply can not run a Series wound motor without a load on it.

I would look on Ebay for a cheap Altrax 48volt golf-cart controller, just to be safe and take better care of the batteries and motor.