I am looking at a motor to buy, and i want to do a compression test on it. Can you do a compression test with no transmission on the motor. And if Yes. how?

 

Yes you can. All you need is the engine to turn over (crank).
Either you can eliminate fuel, or spark.

 

yes you can, manually crank it over by hand, but it's not as accurate as a leakdown test

 

As long as the motor is still in the engine bay and/or can be cranked, you don't need a tranny attached to it. You may have to mess with the neutral safety switch, as there would be no tranny hooked up, but I'm not sure.