KZ 550 LTD Blown rings?

Hey all, working on a friends bike for him. Hes got an 1980 KZ 550 LTD. Since he got it, it's been burning oil, about a quart every two weeks (he rides a lot) and last night it died on him. The symptoms are: hard to start without giving extra throttle, when I do get it going it has VERY little power, can barely get up to 10 mph in first gear. I assume its blown rings, I'm about to go out and to a compression test but I don't have the service manual.

Does anyone know off hand what the PSI should be? I assume around 50-70 like most other bikes of the same age.

Where do I buy new rings? I looked on ebay buy they are very expensive ($50+ per set, I need 4). Are they just wore down, do I need to replace the pistons as well?

I have done a top end rebuild before on a 440, but now I have twice the cylinders.

Thanks for all your help! If I do have to do a top end rebuild I'll be sure to take PLENTY of pictures and document as best as I can for others to check out.

Courtesy of KZr Member loudhvx

General
home.comcast.net/~loudgpz/GPZweb/index.html#home

Service manuals
home.comcast.net/~loudgpz/GPZweb/Mnls/Mnls.html


Good Fortune!

It needs to be much higher than that. Below is a link to a (crummy IMHO) Clymer KZ550 manual. It will download using Internet Explorer, but Firefox gets confused when downloading it. On Page 11 is says normal compression is 130 - 160 PSI but the engine may start with as little as 100 PSI. The genuine Kawasaki Service Manual for the KZ650 shows the bottom service limit for the KZ650 is 114 PSI with less than 14 PSI difference between cylinders. I would suspect the KZ550 spec is somewhat similar. Compression should be checked with the engine fully warmed up, all spark plugs out, and the throttle open all the way. Ed

www.theotherstyle.info/manuals/bikes&atv...0%5b1979-1985%5d.pdf

Thanks for the fast replies! I didn't know the bike had to be warm, makes sense since the cylinders will expand when it's warm. I did a cold compression, so these results are not exactly "correct" but it's a start.

Cyl1: 135 psi
Cyl2: 125 psi
Cyl3: 120 psi
Cyl4: 140 psi

I also took a picture of the spark plugs because I know they are good for referencing engine problems.


EDIT: More info.
The plugs are about 1000 miles old. I'm going to do a warm compression test soon, but my other buddy needs help fixing his truck exhaust first. Thanks again!

As Patton mentioned, there are at least 3 manuals for that motor linked in my signature. The A and C models' motors are the same, both use A motors, actually.

Cylinder 1 seems to be different.

You should check valve clearances, but read the valve train warning first (in my sig), and check the valve timing diagrams on that page too.

That may help the starting/running issue, but unfortunately, probably won't help the oil issue.

Okay, so I went and did a proper compression test. It was hot out today, around 100, so I let the bike run for 5 minutes to get warm. With the throttle fully open I was getting 145-150 PSI on every cylinder. So this makes me think I do not need to replace the rings.

Now I'm thinking it's going to be a coil issue. Could it be the coils are going bad and when the bike gets warm they get hot and get too much/little resistance? The bike is hard to start, really hard now, and it seems like it's only firing on one or two cylinders.

What I'm going to do tomorrow is check the ohms on each coil, see if they are correct and then pull the plugs out and make sure I'm getting a good spark. Any other suggestions?