New Problem

Pulled the plugs and it looks like it is running lean with the plugs showing off white instead of brown. Ran a compression check and it has between 60 on the low side and 90 on the high side. Guess I am going to pull the head to look and see. If it was the rings it seems like it would smoke and be fouling the plugs. It had set up since 85 without running except for a short trip up the street and back ever several years. I wonder if the low comression could have anything to do with it running lean. Wg said the carbs ran fine on his test bike which I'm sure has good compression.

Before you go any farther, check the valve lash.

Of course, I don't have a clue what model of KZ we are talking about (since you didn't say), but it applies to all of them.

Post edited by: steell, at: 2007/08/23 23:20

I checked it when I first started working to put it back in shape but I need to get a metric set and spend some time with the book to get it right. The first time I did it everything looked ok but now I'm second guessing everything. I can't believe how good it runs with such low compression. I think it might be scary with good comp. Or not.

are you sure the guage is good?

Could you add the year, model and location to your signature to give folks an idea of what bike you've got.

Could you add the year, model and location to your signature to give folks an idea of what bike you've got.

76 kz900 a4
wiregeorge 28 mm
vance and hines four into one
k&n filters
dyna-s ing.
accel coils and wires

Post edited by: Handcannon, at: 2007/08/24 08:46

I assume so since it is brand new but who knows for sure. I guess I should check it.

How did you measure compression? Hold throttle wide open when cranking? Lots of folks forget to do this and the compression readings will be bogus.

... warm engine
... remove spark plugs
... insert gauge tip or screw in gauge tip
... crank engine over a few times to pump up gauge

If the bike runs decently, it is hard to believe compression is down in the 60s. Next thing to do is check valve clearances using a set of metric feeler gauges... makes shim selection easier. If you don't have a manual, I have a "how-to" on our website that has pics.

Use a leak-down tester.
It is much more precise and easy to use.
I test every engine this way. I can usually tell if the compression loss is from intake valve, exhaust valve or rings.

sorry. Duplicate entry

Post edited by: FloridaBiker, at: 2007/08/25 15:54

sorry. Duplicate entry

Post edited by: FloridaBiker, at: 2007/08/25 15:54