Blowby Causes?

I ride a KZ550 and recently experienced a bout of blowby. Now, I know blowby is caused by bad rings or poor ring seating. Are there any other causes? What should I be prepared for when I start the engine rebuild? Are there other things that could cause blowby?

To give a little background: I was 3/4 of the way through a long ride when the bike lost some power going up a hill. I looked down and there was a huge amount of white smoke coming from the engine case breather. I pulled over, called a friend and trucked it home. Since then I've checked compression in all 4 cylinders (plugs out, strong battery) and from left to right it's 30, 100, 90, 120. Cylinder 1 is super low. I'm assuming that's the cylinder with bad rings.. correct?

On a side note... is there anything I can do while I have the engine torn apart to increase compression in 2 and 3?

Thanks for the help yah'all!

How long since your last valve adjustment?

Good question. I checked valve spacing a month ago and made some adjustments. The spacing is in spec now. However, I haven't seen the seats... thats probably the cause for the lower compression in cylinder 2 and 3 huh?

Had this myself recently, likely a rings problem. Hopefully you have not junked the cylinder too. Sleeve could be pressed out and replaced or bored out oversize.

Light hone and new rings - if the piston /bore is within spec, plus valve grind in and clearances would improve your compression on all..

kzrider.com/forum/2-engine/599063-thar-s...lows-tyrell-s-gpz550