Intake valves staying open. 1984 ZN1300

Bike would turn over but not start. The intake valves are staying open. I checked the valve clearance and it was below min spec (-.003mm). I put .10mm smaller shims in across the board and they are still -.003mm. I thought someone had botched a valve job at first but now I'm not so sure. Is there a common intake valve issue with these engines?

Hi Ian,

Welcome to KZ1300.COM.

I don't entirely understand the problem. You had less than 3 thousandths of a mm. You replaced the shims with ones that are 100 thousandths smaller and you still have the same clearance?

Bill

I suppose that if the first clearance was actually 0, the shim was still touching the cam when the cam was pointed directly away from the shim, a valve, that wasn't on it's seat, would move up when the shim was changed.

Yes, .10mm smaller shims didn't change the measurable gap. (My feeler gauges have .003mm minimum.) All of the exhaust valves were with-in spec. Thinking on it, the only thing that makes sense is a cam timing issue. There seems to be good tension on the cam chain though.

After thinking this through more thoroughly I think someone must have been into the engine at some point. The only thing I can think of that would cause the valves to remain open on all 6 cylinders and the valve clearances to be immeasurably small is incorrect valves (too long) or improperly ground seats. If it were just a couple cylinders I could think of several catastrophic reasons for a valve to remain open but the likely hood of something occurring to all 6 intake valves is pretty small.

Now it will be a game of chasing stupid. Think of dumb things someone may have done and check it as I dig deeper into the head. First stop will be pulling the cam and buckets out to make sure no one put something on the underside of the bucket.

Hi Ian,

I was thinking the same thing: The only two options that would present as you describe are a too long valve or a too deep a valve seat.

I don't believe these engines use buckets. The cam pushes directly against the shim.

One way to check to see if there is no clearance is to rotate the cam away from the valve and try to turn the valve lifter with your finger if there is any clearance the shim and valve lifter will spin.

Good Luck
Bill