Compression test- Need Suggestions

I finally got the lower miles engine into the nicer frame... I will post the pic when my friend emails it to me.

So the engine is all bolted in and hooked up the wiring harness. Do I have to hook up the exhaust pipes in order to do the compression test? The Haynes manual doesnt really cover doing the test this way.

Can I just hook the battery up to it without the pipes and crank the elec starter?

Thanks!

Post edited by: terps19, at: 2007/11/11 10:58

You dont need the pipes on for a compression test just hold the throttle wide open

Thanks Katjbus

I dont have the carbs on either- so I dont have to worry about holding the throttle open. Thanks for the info and I will post what happens later today!

I just hooked up a charged battery and all the lights came on... good sign. I hit the starter button once for a split second and I heard the engine crank. ANother good sign. Now I will do the compression test after dinner and see what is what!

I hooked up the engine and battery yesterday- lights come on and engine cranks. Carbs and exhaust are not mounted.

I tried to do a compression test with these steps:
1. Removed spark plugs one by one and put them in order they were taken out.
2. Hooked up the compression tester to the far left spark plug hole if sitting on bike using the 14 mm adapter- the threads on the 14 mm are longer than the rest as well. THe tester was bought at Advanced Auto Parts for $35 came with three adpaters (10, 12, 14 mm).
3. Engaged the clutch
4. Turned the key (lights come on) and hit the elec starter for about 3-4 seconds and release and repeat about 3 times.

There was no reading on the compression tester and I dont understand why. I tried it with the 14 mm adapter screwed in tight and once leaving about 1/2 of a turn until tightened and still no reading.

What am I doing wrong? The engine is connected to the hiring harness and bolted into the engine- carbs, exhaist, airbox/air filters not hooked up.

Thanks for any advice

What about the other cylinders?

does the guage bounce when you are cranking the engine? somtimes the schrader valve in the testers go bad or maybe there isnt one in it! Did you run the test on the other cylinders?If not you should that will tell you alot more. if you dont have any compresion it could be as simple as tight valves!?

All the other cylinders have no reading as well.
When I hit the elec starter it just sounds like something is spinning or turning.

Again the engine is only bolted to the frame and hooked to the wiring harness. Exhausts, carbs etc are all off the engine.

Any ideas?

me thinks its user error

Have you tried a finger compression test? Try blocking off one of the spark plug holes with your finger. That should tell you something...

Three things:

(1) The engine is not actually spinning, it's just the starter you hear.

(2) Your compression tester is not working.

(3) There are no pistons or rods inside the motor.

Personally, Id guess number one or two.

If it actually has compression, and you are spinning it with all the plugs removed, then you are going to hear the compression escaping through the plug holes, it's pretty hard to not hear it.

It is very well possible that the starter is spinning but the starter clutch may be slipping and not turning the motor over.

Take the right side round cover off and see if the timing advancer is rotating when you hit the starter button, or look down in the plug holes with a LED penlight and see if the pistons are moving.

Thanks steell...

I am pretty sure it is just the starter I hear as I dont hear anything escaping from the spark plug wells/holes. When I put my finger over one of the holes I can keep it there while I hit the elec starter.

I will take off the right side cover and see what is what. If the timing advancer is not rotating then what would be the next step testing the starter clutch? If it is rotating then I am guessing I am doing the test wrong.

The starter cover is off and the clutch cable is not connected.

Thanks for the suggestions. I sure hope somethig works!