Checking engine compression

[alph]

All right, I went to check my engine compression and I’m getting some way wrong numbers!  There is no way that my engine can be running with numbers like 45# in one cylinder and 90# in the other!  So I must be doing it wrong! 

What I’m doing is removing all six spark plugs, and cranking over engine until the gauge stops going up.  What I’ve found out is that I’m supposed to leave in the spark plugs?  Warm the engine to running temp, then remove ONE spark plug, test that cylinder, then re install it, go to next?  With throttle wide open?  So, is that right?

Thanks
Al.

[DeathWishBikerDude]

I would never remove or install spark plugs from an aluminum engine when warm.
You'll want the engine cold,plugs removed and coil disconnected.
Crank the motor to get a reading.

[PatrickDoss]

I would suspect a bad guage.  You're right about the engine wouldn't run with 45.  It should run with 90, but that's still way low.

[alph]

I checked the service manual and it says to warm the engine to normal operating temp, stop engine, remove spark plug caps, remove one spark plug at a time and test the compression of that cylinder!  I’m just wondering if anyone else has tried to test their compression and has gotten the same results as I have with all plugs out and a cold engine. 

Tomorrow I’ll be testing my compression in the manner of the service manual, I’ll post my results then.  Hopefully they’ll be closer to the 170 # mark!

[Madmike]

.. they want the throttle wide open as well, ...

If one cylinder is reading way off then I would suspect that cylinder, there is nothing wrong with releasing the pressure off the tester and taking another reading on it to see if the result is repeated.  You may have a bad schrader valve in your tester and need to replace that as it could be sticking - get more at any tire shop or an automotive supply.

If all cylinders are low I would be looking to borrow a compression tester from somewhere to see the results with a different setup before I wrote off the engine. 

If just one or two cylinders are low then you can follow the procedure s in the manual to help identify the probable source of the problem - rings or valves.  Again if you doubt your results see if they repeat before ripping and tearing.

Why are you checking your compression??  Just to establish a baseline - or do you suspect that there is a problem??

[R J]

I'll ask the dumb question.

What problem are you having to suggest you do a compression test?

In 242,000 + miles, I have only pulled 2 compression tests, less than 2# loss between the 2 tests on the cylinders.  Was a waste of my time and riding time.....

[alph]

Why are you checking your compression??  Just to establish a baseline - or do you suspect that there is a problem??

it's like this, went for a ride with a friend and asked him if there was any white smoke coming out of my exhaust, he said a little, so i want to know if it's a cylinder ring or valve or antifreeze leaking into a cylinder.  if it's small now, i'd like to know what to watch for.

[Patrick]

wrong, but, I would doubt its with your engine.. I know the BOOK says to leave the sparklers in on the cylinders not being tested,,but,, thats just plain wrong..[There are a few mistakes in that book and that may be one of them].. You should run the engine just a bit, remove all sparklers, open throttle and test away.. All compression gauges are not created equal and will read differently,,but,, not like yours is reading.. It sounds to me like you may be using a hand-held gauge and it may not be fitting correctly and is leaking[around the plug hole].. Try and borrow a screw-in style gauge.. When testing watch the initial reading and the last [should only take about 5 or 6 cycles].. The important thing is that all cylinders should be within about 10# of each other.. Try this again and let us know what happens..

[DeathWishBikerDude]

I wouldn't waste my time with a compression test.
My valk since new,has always smoked when cold,sometimes white,other times black.
Once warmed up,the smoke is gone.
The valk motor is bulletproof,I beat the hell out of mine daily.

[XXTi]

Since I just got my bike, I adjusted the valves, did a compression check and replaced the plugs (13,700 miles).

I know it was probably unnecessary, but I wanted to get a baseline to compare to future readings.  FYI, all my valves were just a bit loose.  The plugs were really OK, but I replaced them anyway.

I did the compression test per the manual.  Warm engine, one hole at a time, etc.  The first time I checked it I only got 90 PSI and just about freaked out.  Then I remembered to open the throttle and everything was fine.  All the cylinders were within a few PSI of each other and my guage read about 165 PSI.  I know the book says 170, but I attribute the difference to gauge error.

I hope this helps.

[Ricky-D]

The main result from a compression test on the motor is a comparison of the cylinders.

The total compression is arbitrary depending on your process and gauge and any other variables.

As long as you are consistent in how you perform the testing the results should be credible.

[Patrick]

STUFF happens.. I checked the compression on the first bike[ both were '98s] just for the heck of it one fine day after riding it for almost 2 years and #6 was low no matter what I did.. Honda was of no use/help what-so-ever,, you know,, they don't make defective products and I did something to ruin that cylinder.. Now the engine ran great even with that low cylinder.. Upon tear-down I found that the piston land was damaged pinching the rings,, it looked as though it may have been dropped while or prior to assembly and some one decided to stuff it in the hole anyway..It took months but Honda then gave me a piston and one set of rings for that piston,, they are such a wonderful bunch of folks to deal with.. So that was the bike I decided to play around  with and I got another one for normal riding..