Intro and Compression question

Hey all!
Picked up a real nice 1977 KZ400 today!

Wasn't running for previous owner, his mechanic suggested rebuilding the carbs.

The bike has 6200 miles and with some fresh gas, and a set of plugs, 20 minutes on the charger, it fired right up. Bike is all stock. Air box and all.

First impression, carbs need to be cleaned for sure. Seems really rich, doesn't want to idle off choke, etc. That part I am pretty comfortable with. Carb inlet rubbers are a bit cracked, right side worse than left. He bought one replacement which I need to install yet.

Also noticed the right side pipe has a couple holes on the bottom, well tears would be more accurate. Almost looks like a big backfire ripped a couple holes or something! A bummer for sure. Rest of the bike is rust free and super clean!

Pulled plugs, did compression check (throttle wide open, both plugs out) and that's when it got a little more interesting:

Left side 165 psi
Right side 153 psi (not sure it matters but this is the side with holes in exhaust)

Now this is probably pretty basic to you guys, and maybe has to do with the valves? The compression difference I mean. See, the rest of the bikes in my garage are all 2 stroke Kawasaki's! So this valve thing is a bit new to me :laugh:

The bike sat for at least the last 7 months. If that helps at all. Any advice would be greatly appreciated. Sorry for the long first post.

Thanks!

Welcome aboard! You can check valves, etc. but I wouldn't let those compression numbers worry me at all if I were you (in fact you may want to brag about them ). They are actually great numbers, especially for a 36 year old bike! If you take a look at Table 21 on Page 114 of the Kawasaki Service Manual in the link below, you will notice that "Standard" compression is 142 - 156 psi. The service limit is a mere 107 psi with no more than 14 psi difference between cylinders. So your current compression is really great as it is every bit as high (and then some) as standard and the psi difference between cylinders is within spec. Ed

home.online.no/~ivbekkel/Workshop%20manu...al%20P.101-p.136.pdf

That's good news Ed! Looking at parts prices now, exhaust seems a bit on the high end just like with the Kawi Triple 2 strokes...not quite as bad though so its a refreshing change!

May go with a 2 into 1 pipe setup (found a rust spot/ weak spot on the right side pipe too ) depending on what I can find...

Thanks again!