no compression in # 2,3

i recently bought a '82 kz550 ltd that didn't run but did the previous year. after many many wasted hours of trial and error I discovered cylinders 2 and 3 have absolutely no compression. i checked the timing which is spot on, checked the clearance in all the valves which all were within limits, and even tore the head off to inspect for holed pistons, damaged rings or burnt/bent valves but nothing seems to be wrong. the only thing i noticed that wasnt right is the worm drive for the tach doesnt make contact with the cam drive, but that shouldnt affect the compression. ive had the top end taken apart so many times now it just makes me want to abandon the whole project and look for another bike. at least i know everything else is in great working order on the bike, but does anyone have any suggestions, or has anyone experienced a similar problem? thanks for any consideration into the matter, ive already learned a wealth of information from this site and the users so far...

The KZ1000 that I just did a topend on had the same problem, with lots of head scratching. 2 and 3 had no compression 1 and 4 had some....

turns out the head was warped, you might be able to machine back to specs but I had to get a new (used) one.

YMMV

oh... and have a machinist check for you, mine looked fine with the crappy level/straight edge that I had...

Post edited by: Beepy, at: 2007/06/28 14:54

When you had the head off, did you check to see if the valves were seated, fill exh. and intake port with solvent and see where it leaked out? Did you check valve clearances, did you have the valves out or if some carbon in the exh. ports flaked off and when the valve was open will cause it also

did you pull the cyls, what kind of shape are the rings in?

if the motor is back together id say check valves again,if they are close run compression test.if 2 and 3 show low copression put a little oil down cylnders and see if they come up ,if they do check your rings if not check your valves.when you have head off of bike fill exhuast ports full of solvent or water,the take an airhose and blow around face of valve and seat if you see bubbles in port theres your problem then repeat process on intake side;)

it's both amazing and frustrating that such a small valve leak could cause so many problems.... needless to say that was the culprit... thanks for the help guys

no problem glad you got it fixed:)