81 kz1000 low compression

I have a 1981 KZ1000 which has sat for a few years that I just purchased. The bike is really lazy in the lower RPMs. I automatically though low compression because of that, plus the way it starts. Starts way low in the rpm range and takes a little while to rev up and idle. I did the compression check and from left to right compression is 100, 80, 30, 100. When doing the oil test on the one with 30 it only goes up to about 60. Does this mean it's a valve? The bike has sat for 2 years so is a sticky valve a possibility? Previous owner guarantees that it had no loss of power when parked and that anything wrong with it happened during storage. Any suggestions on what to do to diagnose this problem? Thanks.

you probably have stuck rings, you can try to put some marvel oil in the cyls and let it sit, but I think you will still wind up replacing the rings

tyhoppy wrote:

I have a 1981 KZ1000 which has sat for a few years that I just purchased. The bike is really lazy in the lower RPMs. I automatically though low compression because of that, plus the way it starts. Starts way low in the rpm range and takes a little while to rev up and idle. I did the compression check and from left to right compression is 100, 80, 30, 100. When doing the oil test on the one with 30 it only goes up to about 60. Does this mean it's a valve? The bike has sat for 2 years so is a sticky valve a possibility? Previous owner guarantees that it had no loss of power when parked and that anything wrong with it happened during storage. Any suggestions on what to do to diagnose this problem? Thanks.

If not already done, would check valve clearances and adjust as necessary by re-shimming to factory specs. Then perform compression test again (holding throttle wide open during testing).

Good Luck!

When doing the oil test on the one with 30 it only goes up to about 60.

Having done a "bunch" of compression tests, the above says it's not rings.

I assume you did the test with oil on the other cylinders and they all showed about the same increase? I hope so, because they are all real low.

A leakdown test is a much better way of diagnosing the problem, but you still need to check/adjust the valves before doing anything else.

You did have the throttle wide open during the test, right? It makes a huge difference.

Yes throttle was wide open. what's the easiest way of taking the valve cover off... doesn't look like enough room between the frame and the cams. Also, anyone know the specs that the clearances should be? I ordered a manual but it's not here yet. Thanks.

tyhoppy wrote:

Yes throttle was wide open. what's the easiest way of taking the valve cover off... doesn't look like enough room between the frame and the cams. Also, anyone know the specs that the clearances should be? I ordered a manual but it's not here yet. Thanks.

.002 - .004 inch (.05 - .10 mm)

Remove fuel tank and all sparkplug caps and all valve cover bolts. Gently manuever and wiggle valve cover between the frame and engine. It's a snug fit, but should pull free without having to loosen any other parts.

Good Luck!

tyhoppy wrote:

I have a 1981 KZ1000 which has sat for a few years that I just purchased. The bike is really lazy in the lower RPMs. I automatically though low compression because of that, plus the way it starts. Starts way low in the rpm range and takes a little while to rev up and idle. I did the compression check and from left to right compression is 100, 80, 30, 100. When doing the oil test on the one with 30 it only goes up to about 60. Does this mean it's a valve? The bike has sat for 2 years so is a sticky valve a possibility?

I wonder if it's possible fuel could have seeped down and into the intake and gummed up some of the valve seats? If it sat that long, the gas would have turned to varnish like glue.

Patton wrote:

tyhoppy wrote:

Yes throttle was wide open. what's the easiest way of taking the valve cover off... doesn't look like enough room between the frame and the cams. Also, anyone know the specs that the clearances should be? I ordered a manual but it's not here yet. Thanks.

.002 - .004 inch (.05 - .10 mm)

Remove fuel tank and all sparkplug caps and all valve cover bolts. Gently manuever and wiggle valve cover between the frame and engine. It's a snug fit, but should pull free without having to loosen any other parts.

Good Luck!

You can also buy some more space by removing the coil on the side you want to pull the cover out on.

So both the intake and exhaust valve clearances should be .002 - .oo4 inch?

tyhoppy wrote:

So both the intake and exhaust valve clearances should be .002 - .oo4 inch?

Yes. All the same.

Personally,I would keep that shim gap on the higher side.(.004)

The term quote: previous owner said unquote is one of the silliest things that any new owner can use. The previous owner is likely the WORST source of info on a bike that you could use.

Your valves either lack clearance or the top end needs rebuilding. I can't imagine this bike running much at all with two cylinder down that far (80/30) but I would definitely adjust valve clearances before yanking the top end. A sticky or bent valve is a possibility. Even though the rings MAY be OK based on your oil compression check, I would consider removing the pistons and measuring the cylinder bores (get a manual) and piston diameter and checking to see if the clearance was within spec. If so, hone and install new rings while you go through the cylinder head.