Worn Out Compression Rings | Surf’s Up, Oil Level’s Down

By Jerry Smith, Photography by Motorcyclist Archives

Q: I have a 1978 Kawasaki KZ650 that I got in trade for a surfboard. The bike didn’t run when I brought it home, but after some cleaning, tinkering, and rebuilding, I got it started. I removed the stock airbox and put on pod filters; I haven’t rejetted the carbs yet. I rode it about 30 miles to break it in and get a feel for how it ran. When I got back I noticed the engine was very low on oil. On further examination I found it was leaking badly out of the crankcase vent, where I attached about 8 inches of hose capped with a filter. I didn’t think that much oil could come out of the crankcase like that. What’s happening?
Rory C. Byrd
Via e-mail

A: Is it too late to get your surfboard back? Your KZ’s engine probably needs a top-end teardown. Best guess is the compression rings are worn out or gummed up and stuck in their grooves. Either way, the pressure in the cylinders is blowing past the rings down into the crankcase and pressurizing it, forcing oil out of the breather. If the bike smokes when you back off the throttle, the oil-control rings are probably shot, too. Even if they’re okay, install the new ones that come in the rebuild kit with the compression rings.


Q: My son is the second owner of a 1981 Honda CB750C with 20,000 miles on it. It seems to stop, go, and handle just fine, but the centerstand contacts level pavement on the right leg and left-side foot tang; the left leg does not touch pavement. The result is a wobbly bike when on the stand. There is no apparent crash damage. How can we determine what the problem is? How can we check the frame for straightness?
Rik Davis
Perrysburg, OH

A: The problem with the centerstand is probably just that—a problem with the centerstand. If the frame were bent badly you’d notice it when you ride the bike. Examine the weld between the tang and the stand for cracks, and compare your stand to another from the same model to see if the tang is bent.

By Jerry Smith
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