1978 KZ650 SR Compression Question

Hi I just got a new to me 1978 KZ650sr. The bike had sat for a while when it was sold the first time. The new owner had tried do get it running but couldn't. So I bought the bike as a project. Mileage is fairly low the odometer shows 16000Km Carbs are very gummed up and need cleaning and are off the engine.

First thing I did when I got it home was pull all of the plugs and run a compression test. The results I got are 1:125 2:120 3:117 4:136 I then put a some oil into the cylinder and ran the test again. This time I got 1:130 2:135 3:130 4:150. Both tests were done on a cold engine

From what I have read these values are on the low side and all 4 should be within 10% of each other #4 breaks that rule. I don't have a lot of experience with these engines so are these values close enough to the low side of spec to worry about. I'm going to check the valve lash tomorrow to see if I that's part of the problem.

I want to do what is required to make this bike reliable but don't but am on a budget too.

Any advice would be greatly appreciated. If this has been covered before sorry please send me the link. I looked but couldn't find it.

Thanks

Put some penetrating fluid in the cylinders and let it set until you have everything else done. If it has been sitting for a long time the rings may be stuck and that should free them.

Check/adjust the valves also, compression should have jumped up a bunch when you did a wet check.

Welcome to KZr gargoyle.

Something isn't quite right here.
As steell pointed out, the dry and wet readings you're getting are barely showing any diff at all.:huh:

Are you performing the compression test with the throttle cranked all the way open?
You'd be amazed at how much of a diff that will make in your bikes compression readings.

I think once you put some easy miles on her the compression will go up. My engine had similar compression to yours, and by the time I could check it again, a few thousand miles later, all were above 150. Oh, I had also adjusted the valves between the readings too.

Thanks for the welcome! This place is so cool.

I did the tests with the carbs off of the engine. They are going to be cleaned.

I'm going to try the penetrating oil. Any suggestions as to which type? I've also heard the diesel works. any ever tried it?

I also just noticed an oil stain across the front of the engine at the head gasket (see picture). Looks like the head gotta come off

Welcome.

That oil stain doesn't look too bad to me. I can't really see it though.

I agree that those compression numbers aren't to be worried about at the moment.
Clean those carbs and do a tune up on her, and see how well she runs.

Add your bike info and location to your signature line in your signature, found in the profile area.
Helps others when answering your questions.

Also post up a picture of the bike. We love to see them.

Hey rstnick

Here's a picture of her with the tank and seat just set in place. Can't show her naked :blush:

You can see the oil stain better from this angle.

Noticed your in Ontario. If your in the southern end do you know a good place to get parts like valve shims and such.

gargoyle wrote:

...going to try the penetrating oil. Any suggestions as to which type? I've also heard the diesel works...noticed an oil stain across the front of the engine at the head gasket (see picture). Looks like the head gotta come off.... /quote]

As to penetrating oil, PJBlaster would be good. Have heard good things about a similar "Kroil" but never used it. Some folks use ATF. Allow to soak for several days. And keep adding supplementary doses so it stays good and wet inside the combustion chamber.

As to the oil leak onto cylinder fins, it's often caused by a leaking exhaust gasket, especially where an old already crushed gasket is re-installed instead of a brand-new gasket. Or some make-shift gasket is fitted, or gasket is missing. Or the nuts might be loose that hold the exhaust clamp in place. (Don't over-torque via Godzilla method and risk snapping off the stud.)

Click here for > Z1E Exhaust Gasket

Good Luck!

Z1enterprises or others in the links section should have some of the stuff your looking for.
Z1E been used by lots of members here, and I've never seen an unsatisfied customer. If it's not on their website, call them as some things are not listed on the site.
I'm don't know of a place in Southern Ontario that would have them.
I had my valve clearances done by a shop in Newmarket. I should have done it myself to have saved some money at the time. Live and learn.

Check out the link in my signature, Southern ON KZR Chapter.
Hope to have a bunch of KZs in Paris June 14th. at the CVMG Swap Meet.

gargoyle wrote:

Any advice would be greatly appreciated.

Tune it up and ride it. Thoose comp readings are better than a lot of old bikes buzzing down the road.

gargoyle wrote:

I also just noticed an oil stain across the front of the engine at the head gasket (see picture). Looks like the head gotta come off

My 750 twin has always seeped oil along the front of the head gasket for as long as it lived, including after both rebuilds with new head gaskets. The gasket width is thinnest there, the cam drive chain is always spinning oil against it, and I have never been able to stop the seepage.

I roll up a section of paper towel real tight and press it into the fins against the leak to sop the oil. At least that keeps if from running down and along the fins.

Patton wrote:

Have heard good things about a similar "Kroil" but never used it.

I (and many other shooters) use it a lot for cleaning gun barrels. I think it penetrates into gaps down to about a micron, so it gets under and loosens most anything that isn't "flame burned" onto steel. For rings rusted to a cylinder, it is probably pretty good but they may still need persuasion.