Low Compression?!

Greetings All,

Ok, I recently acquired a KZ440 '82 with about 3,000 original owner miles. The thing is cherry but dusty. I have a Clymer Manual and have purchased all of the tools listed for a Full Tune-up. While going through the tune-up, i checked piston compression (cold engine) after adjusting the valve clearance (first time ever carrying out such a procedure). What I found was disturbing... ~30 psi!!! I went through the forum's posts and tried putting 1/4 tablespoon of oil into the spark plug holes, then remeasuring compression. No change. Which leads me to believe it is the valve clearances. My understanding of valve clearances leads me to believe that the valves are not fully closing.

I AM a novice wrencher, and that was my first time going through valve-tappet clearance adjustments, but I know that I left a gap between the tappets and the valve/head. Any advice or hunches? This afternoon I'll be checking the valve clearances again, just to make sure there is still a gap.
Thanks!

In addition, I've fouled two sets of plugs and they looked black and wet. Couldn't distinguish between oil or gas smells at the time, but will definately do a full sniff comparison with a can of oil and the gas tank.

When you did the compression test, you did hold the throttle wide open, right?

I don't think the motor would even run with only 30 psi of compression.

I think a leak-down test is in order. This will tell you where you are loosing compression--intake valves, exhaust valves, or past the pistons.

There is a document in the filebase that describes how to do this, and how to build your own tester.

It can be found here .

Post edited by: Skyman, at: 2007/05/01 17:31

with compression that low and with mileage that low i would suspect that a valve or valves are stuck open, probably from some old goo in the engine. i would start by pulling the tappet caps and seeing if you have a crap load of clearance = valve stuck, or none at all = clearance too tight.

steell wrote:

When you did the compression test, you did hold the throttle wide open, right?

I don't think the motor would even run with only 30 psi of compression.

Throttle was wide open. Made sure of it.


The strange thing is the motor does run while the thing is choked, but even half-way off choke it dies. A complicating factor with that situation may be the addition of new emgo pod filters and haven't gotten to adjusting the idle mixture/idle speed, and hadn't considered rejetting the carbs until today.

flht1997 wrote:

with compression that low and with mileage that low i would suspect that a valve or valves are stuck open, probably from some old goo in the engine. i would start by pulling the tappet caps and seeing if you have a crap load of clearance = valve stuck, or none at all = clearance too tight.

Now that you mention it, I did not have this problem before I used some SeaFoam in the gas tank. Perhaps the sea foam mobilized some gunk from the carbs and got stuck in the intake valve?

I'll take off the top of the engine and get a better look at the camshaft/valves tonight.

perhaps some stuck rings also?
also it seems unlikely that an engine would run with 30psi of compression, are you sure you have an accurate compression tester?

flht1997 wrote:

are you sure you have an accurate compression tester?

Ha. Well, no...in my professional scientific opinion. I have not calibrated this compression tester and I picked it up for $40 from NAPA. I followed t he directions in the box and in the clymer manual. ::shugs::

that was supposed to be : : shrugs : :

flht1997 wrote:

perhaps some stuck rings also?

So the crankcase breather puffs quite a bit when I have it running with the choke full-on. I took a good look at the oil level and its above the top-mark.

so I feel

1. Either the rings are bad/stuck and engine compression is being lost to the crankcase

or

2. having too much oil is hard on the engine...which somehow results in puffing?

OK , Dont go crazy here ........

I dont know all that much about 440s but I KNOW BIKES.

If you have to much oil in it ,change it .

If you just put new air filters on the bike , take them OFF,you dont need them to test anything .

Gas tank in your way take it off.

Old gas in the bike ? dump it ,rinse it out and put in 1/2 a tank of fresh,when you are ready to run it .

THEN , check your valves ,leave them loose for this , you dont want to go for a ride now , your just trying to find out whats going on inside without taking it apart.