View Full Version : compression test on engine that is not in frame....

06-25-2014, 6:22 PM
I was wondering if you can perform a compression test that is not connected to the frame or anything electrical?

want to see if the motor (shovelhead) needs rebuilding or not before i put it together.

06-25-2014, 11:37 PM
Yes you can, helps if its bolted down.
Easier to do a BDC leakdown.

06-26-2014, 8:07 AM
Leakdown is wise, but if the engine is out of the frame and condition is unknown it would be far wiser to do the leakdown AND pull the heads and cam cover to inspect.

"There is never time to do it right, but there is always time to do it over."

It ain't rocket surgery and is a shitload less work than stuffing an engine, finding it's fucked, then pulling the engine for repair.

06-26-2014, 2:27 PM
I always pull the top end to know what I have, aint gunna hurt to check them rods. I pull the valves and look at them also or atleast toss some carb clean or starting fluid gas on top of the valves and blow air through the ports to see if you have leaks
good guides will have suction when u put ya finger over the top and pull the valve. lapem kibble whites and check the springs if it don't look to bad

07-19-2014, 10:51 AM
Yes you can, helps if its bolted down.

That's exactly what I did with mine. Engine ran when I bought the bike, and I pulled it to work on the frame. Built an engine stand to make storing the engine easy. Decided to to a compression test just for kicks, so I hooked up the battery to the starter through the starter solenoid switch, then triggered the solenoid using a 12v power source. Worked like a charm. Engine is an inline 4, which may shake a bit less when spinning; in my case, the engine was just in a stand, but not actually 'bolted down'.