I have a Schumacher Mi5 with a 13.5T and will want to race other classes, what do you guys do to change motor classes? Change ESC and motor, re-solder motor, or use some sort of motor to ESC connector for a quick change? I have looked for some good connectors but have not found many, any recommendations?

I would just keep an iron hot in your pits like the old days of hard-wiring batteries and change the motor by un/re-soldering the wires for the best connection. If you're less worried about "best", you can put bullet plugs in between the ESC and motor like on many RTR's.

what would be much easier is to keep the motor the same and just run different profiles on your esc. run a spec blinky class with the timing on the motor cranked to what's safe and then change the esc to a mod profile with boost/turbo and turn down the timing on the can (maybe gear down). unless the guys in mod are really good, you should keep up pretty close to them without all the soldering.

I would make a clamp on the motor (fan mount?) with a small piece of carbon to hold the ESC.

In that way by unscrewing the motor and taking out the servo plug you take out the whole power system.

With the 2nd motor and ESC you can do the same.

Our local track now has a 21.5t and 13.5t fixed timing TC class. I'm planning on finding a spur size that would work for both, as it's the spur change and re-tweaking the car that takes more time than just soldering the motor. I'll have to change ESC settings as well, which I'll do via the hobbywing wifi module as it allows saving different profiles.

The guys at our club are running the same 13.5T motor in both stock and Mod... when running Mod, some will add a little boost to get more top end on the straights, and many 13.5T drivers are beating drivers with 6.5T motors... mostly because they are making up the difference on the infield.

Constantly changing motors between classes will get old really fast. Even changing a transponder between two cars got to be too much in the end for me. I'd just but a second car if I was serious about running a second class.