cold compression test
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Joined: Dec 2007
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From: Knoxville, Tn
Compression Test
Why not just pull the plug wires off the plugs and hit the starter...You will have to mount a compression gauge in one of the spark plug holes anyway if you are going to test for compression.
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Joined: Sep 2010
Posts: 14,744
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From: Phoenix '53, '88, '09 Big Twins
You can do that with points, you can try that with an electronic ignition- and you may get away with it or not.
you can run the motor if the plugs ( removed), are grounded to the motor, so that the circuit is complete- that way the field in the coils may collapse completely
OP, compression checks need be done when the motor is at operating temperature so that all the parts have expanded- this will give better or accurate numbers.
Mike
Last edited by mkguitar; Oct 27, 2014 at 04:52 PM.
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Joined: Sep 2007
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cold compression test
Because the ignition system will blow !
You can do that with points, you can try that with an electronic ignition- and you may get away with it or not.
you can run the motor if the plugs ( removed), are grounded to the motor, so that the circuit is complete- that way the field in the coils may collapse completely
OP, compression checks need be done when the motor is at operating temperature so that all the parts have expanded- this will give better or accurate numbers.
Mike
You can do that with points, you can try that with an electronic ignition- and you may get away with it or not.
you can run the motor if the plugs ( removed), are grounded to the motor, so that the circuit is complete- that way the field in the coils may collapse completely
OP, compression checks need be done when the motor is at operating temperature so that all the parts have expanded- this will give better or accurate numbers.
Mike
Connect solenoid terminal and positive battery connection at starter.
For anyone wanting to know
a cold compression test is performed (I learned this from a very good Harley mechanic.)
1) remove air cleaner;
2) open throttle full;
3) remove plugs and insert compression testor into either cylinder;
4) make a connection between the solenoid terminal and the positive battery cable connection post at starter. (I use remote starter. If not, can cross these connections using electrician type INSULATED wire.
Engine will rotate and let it rotate a few 2-3, 3- 4 times - whatever, until compression tester dial stops jumping/moving up and holds a steady measurement. Then, do same on other cylinder.
Reading for a TC88 should be b/n 150-180 lbs (I think thats it for TC96 and all Harleys but really, Im not sure - maybe someone else knows). Anyway, the readings should be between 150lbs to 180 lbs w/ each cylinder reading w/in 10 lbs of the other = good.
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