650 compression

Hi, Im new here, my names Dan, live in omaha ne. I have about 48000 on a 77 kz650c.I borrowed a compression gauge from the auto parts store and did a compression check on my bike last night. Came up with the following results by first checking my warm engine dry and then adding a little oil to the cylinder-wet/dry:#1;90#/140#. #2;90#/135# #3;90#/150# #4;90#/165#.
These results would indicate some worn rings,although the engine does not seem to be using oil.
I guess I have 2 Questions: Would this amount of wear merit a top end job? And,if all other factors such as timing. valve clearance,and points gap are correct, would it be worth the effort to attempt to sync the carbs with the compression as it is Thanks for your help,
Dan

I misread your post at first. Looks like the rings are wearing. 90 PSI is too low. I wouldn't think that a carb sync would be too affected but I'd do one after the top end breaks in.

BTW, welcome aboard, Dan. You have a lot of company on here from Omaha.

Dan, more questions than answers... 90 psi is barely enough to support life. but is commom in bikes where extended sitting has allowed rings to stick or fuel to slick rings. adding oil will improve these as well as sealing moderatly tight/burnt valves. as a cheep old fart, I would check valve clearances and unless in regualar use, run a tank of gas thru before launching into top -end, especially since std rings may be nla. G

The readings don't really mean much if the bike is running ok and not smoking. I would do a full tune-up (points, plugs, condensers), lube the points cam so it moves freely, check the carb holders, check the valve clearances, synch the carbs (this is REAL EASY!), and check float levels using the tube method. If it still wasn't running well, I would remove and clean the carbs. 48,000 miles isn't really that many miles if the bike has been reasonably maintained. All the stuff I just mentioned will need to be done even if you do a ring job, so why not do the easy stuff first and establish a baseline? You may find that the bike runs great. Ed

Since the two 90 cylinders did not change with added oil, I would wager they have valve problems. Either too little clearance or they just are not sealing well.

when you did the compression test the first time did you have the throttle open all the way if you didn't try it again and i'm sure the numbers will come up als did you kick it or use the electric starter because that can make a differance as well . i would not be to freaked out if the bike is running well, one other thing why did you do a compression test in the first place are you having a problem or just out of curiosity.

The bike is really cold blooded,that is hard to start when cold, and also there is a hesitation when I get on the throttle. I found that my push throttle cable was bad, that might be a big part of the problem. I rode the bike last summer, and went through 3 sets of plugs in about 1200 miles. Plugs appeared to be carboned up, but when I cleaned them it didnt help. Found no continuity through the bad plugs. The bike has 4 into ones, and P.O. had carbs rebuilt by local shop. I replaced intake boots and went through valves this winter, brought all valve clearances up to spec.
I performed the compression test using the kickstarter Right now I cant think of anything else, except that the bike was given to me about a year ago, by a fellow that couldnt start it and his brother was wanted it out of his garage. New plugs and away I went. Still trying to sort it out.
Thanks,
Dan

Whoops! compression test was done with electric start.

As the other guys said, check everything else first. These bikes can be cold blooded but run fine when warmed up. What jets, pilots, are you running? Also consider doing the Wired George Coil Mod . Welcome to KZRider!!