I am looking at a parts bike for $200, and excited about getting a sound, high compression engine as part of the deal.
I know how to test when you have a battery and a starter, but what if the bike is disconnected from battery, starter?
Can you hand crank it and get an accurate compression reading (with a wrench at the rotor?).
Are there any tricks to get this info before you buy?
I would guess a roller starter would be your best bet.
Remember that cold compression is a bit of a crap shoot, normally compression is measured warm, so it may not give you much usable info.
Quote from: struckjm on November 04, 2020, 07:50:48 PM
I am looking at a parts bike for $200, and excited about getting a sound, high compression engine as part of the deal.
I know how to test when you have a battery and a starter, but what if the bike is disconnected from battery, starter?
Can you hand crank it and get an accurate compression reading (with a wrench at the rotor?).
Are there any tricks to get this info before you buy?
do a rolling test in in fourth or fifth gear. Roll and then let out clutch (as if you were push starting)
Did you end up buying a leakdown tester and compressor? If you did, Bring that over and perform a leakdown test
You don't need a relay or the wiring. If the starter motor is serviceable and in place just connect the negative of a 12v battery to a ground on the frame and flash the positive to the terminal post on the motor, the engine should spin.
The other option is to fasten together some pneumatic fittings and a gauge and allow some compressed air into each cylinder and see if it holds pressure. Complicated but not impossible.