Need help with compression problem...

Ok, I picked up a 78 KZ650 Custom last night for free. Here's the story behind it.

I'm the 3rd owner. The guy that I got the bike from said that it had a couple of problems. He believes that something is wrong with the starter. It spins just fine but it seems to not engage. He said that he started it one day and it fired right up with the first kick. Problem was it seemed to have a compression problem to him. He stored it hoping to rebuild the bike one day but he is now 50 and has lost total interest. Now it is in my hands....

Bike is in excellent shape..... this is my first street bike but I own a couple of dirt bikes that I have been riding for years.

I pulled all 4 plugs to do a cold compression test....I know, not the best but here's what I have found. For some reason I cant get a reading on any of the cylinders. I know the compression tester is good due to I tried it on one of my dirt bikes. Also, should this bike be real easy to kick over? Im used to the compression of a 2-stroke 250. I dont know if Im missing something on the test.....

All 4 plugs looked to be burning real clean upon removal..... no oil deposits or anything. Any help or suggestions would be greatly appreciated.

del

With all the plugs out, yeah it's going to be real easy to kick over!

So plug your finger over a hole and kick, is it trying to push your finger off?

Welcome to KZr FreeKZ650.

Not a KZ650 cheap, but FREE? (are you seeing this BadKaw?...lol!)
Lucky you!

If you're pulling the clutch lever in while trying to kick the bike over, that might be where your prob is.
If you look on the back of the clutch lever perch you'll see a plug with two wires running from it, this is the clutch "safety switch". It prevents the bike from starting if it's in gear when you push the starter button.
If you hold the clutch lever in while trying to kick start the bike however, (IIRC) it disengauges the inner kick start mechanism from it's associated gearing and won't turn the engine over = no compression reading since the crankshaft isn't turning and moving the pistons in the cylinders.

And as JMKZHI stated, compression readings should be done with the throttle held wide open to get the best results.

I think the fact he owns two dirt bikes and this is his first street bike is the key.
He is used to primary drive kickstarters found on dirtbikes, those you can kickstart while holding the clutch in.

Sounds like 4R wins this one

To answer the next (unasked) question, the bike must be moving (not just the motor running)to shift into anything other than 1st or neutral

Well.....you guys hit that one on the head. Yep, used to dirtbikes. Don't hold the clutch lever, wow, you get compression.

So..... 130,130,128,70 next question..

I now know there is a need for a top end rebuild. Where is the best place to purchase a top end kit for this bike?

FreeKZ650 wrote:

...compression...130,130,128,70...need for a top end rebuild....

Maybe not - would first check valve clearances, especially the low cylinder.

A FREE KZ650! Wow, you must be living right! Take Patton's advice and check the valve clearances before you start pulling anything apart or buying top end parts. If the valve clearances are ok, do a leakdown test to see where the compression is leaking. These engines are really tough and don't need a lot of work if they are maintained reasonably well. What is the mileage on your bike? My '77 KZ650 Custom has over 45k miles and has never had the head pulled or any other serious work done yet (I'm the original owner, so I know its history). Good luck and keep asking questions on this site. Oh, and post pics, we love pics. Ed

Post edited by: 650ed, at: 2007/09/21 18:07

The bike has 39K on it. What do I need to do to check valve clearance? I want to make sure I do this right. I have alot of plans for this bike so I dont want to start with hacking something....

First thing to do is get a "factory manual", I have a factory and a Clymers manual. They are invaluable for sure! Plenty on ebay. P.S. Free 650 in excellant shape? Will you pick my next set of lottery tickets!? :woohoo:

Post edited by: Bluemeanie, at: 2007/09/21 18:28

Hmmmm..... so am I to assume that I did good with a free KZ650? Everyone keeps mentioning the fact that it was free. I'll pick your lottery ticket for you... I want half if you win

Check out the "Filebase" section of this site (under the KZ Information menu). Lots of good "How To" docs in there that you may find useful, including this one on how to build and use a leakdown tester: tinyurl.com/2747cu

Post edited by: Skyman, at: 2007/09/21 18:36