Could someone please explain the correct way of performing a compression test on a 92 evo and what numbers I should look for. The bike is stock minus exhaust and a jet kit. I've never done it before and get ripped off way too much by the dealers. Reason this has to be done, go figure. Please help or provide me with a link explaining. Thanks

 

 

The utube video is great but they are testing on a cold parts bike.
Will give you the step by step .
1) Get a good quality screw in type of comp. gauge .
2) Run the engine to operating temp.
3) Remove both spark plugs and ground the sparkplug wires to the chassis.
4) Completely open the choke and lock the throttle to wide open.
5) Ensure the comp. tester orings are ok. and screw the tester into the front cylinder spark plug hole.
6) With a fully charged battery , roll the engine over until you see the max. pressure reading on the gauge. Record this reading.
7) Do the same with the rear cylinder .
8) Compare the readings , if you find a varience of more than 10lbs.psi.
come back and we will go furthur through the process.

 

Will an automotive tester work just the same? I know autozone rents certain tools and I would rather do that than buy one . Thanks for the info.

 

Can I just ask why you choke the engine then go full throttle? And just to be sure, I do this before screwing the tester in?

 

He didn't tell you to close the choke, he told you to fully open the choke.
You don't want any restriction of air flow in the intake while doing this test.
Remove the air filter as well.
Yes, an automotive compression tester is what you use to do this test.
You want one that screws into the spark plug hole and has a good o-ring seal on it so the pressure doesn't bleed off. If all you can get is one of the testers that is held tightly into the spark plug hole by hand, get a pal to help you out so that the person holding the tester into the hole is making sure it is held in it firmly...this is to prevent leaks just like would happen if the o-ring on a screw in tester was not sealing.

 

Helps air move into the cylinders. You don't choke it, you make sure the choke is open. As long as the choke and throttle are open while you are cranking.

 

1.Remove the spark-plugs.
2.Ground both leads, this helps prevent damage to the coil.
3.Install compression testing gauge.
4.Hold the throttle fully open (for CV carb models, hold the slide up as well).
5.Turn the motor over until the gauge settles at the highest reading. This usualy takes a few revolutions and I take note of how many it takes for each cylinder in case one takes a lot longer to reach max psi.

If you get a low reading on one or both cylinders you can try adding a little bit of oil into the cylinder via the spark plug hole. Recheck after adding the oil. If the psi went up it would indicate worn rings.
In the event 1 cylinder 10 or more pounds higher/lower than the other, you may have either burnt seat, valve or posibly ring/cylinder issue.

Compression test vidio.


Rent a screw in tester from Autozone-etc., you get the money back when you return it. I check mine every 20K and I'm due..thanks for the reminder.

Ds

 

ok thanks guys. I should probably turn the gas off as well right?

 

Yep!!
John