There are a couple of things you can look for to see what condition the engine is in.

With the glow plug in the engine, slowly turn the crank to top dead center while listening at the exhaust port. If you can hear alot of air leaking between the piston and sleeve, it's not a good sign. When you turn the flywheel over a few times (about 2-3 seconds per revolution), you should hear a nice popping sound from the exhaust. If you hear air leaking during the upstroke, the engine is clapped (d.o.a. - keep your $150 AU).

Bring the piston to the bottom of the cylinder and remove the head. Inspect the sidewalls of the sleeve for scratches and tell tale signs of blow by (compression leak between piston and sleeve will leave a dark line on the side of the cylinder - typically from mixing and matching used pistons and sleeves). If they will not let you do this, keep your money - they are hiding something.

Watch it run at temp for a tank (with load on it) through the entire rpm range. Verify that it can maintain a low idle for at least 5-10 seconds.


Good luck