1981 KZ750 Will not start after gasket change

Hello all,

I replaced the gaskets in my 81 KZ750 because of a slight oil leak, and after reassembly, it will not start (it started and ran amazingly beforehand).
I have checked and checked everything I can think of and whats in the manual (coil wiring, spark, compression, fuel in carbs, battery). It is cranking and air in going through the engine, but nothing happens. I am in need of help!

We might be able to narrow the possibilities a bit if we knew which gaskets were replaced (what was disassembled and generally messed with).

Start with the easy and obvious stuff--

Is the handlebar kill switch set to ON?
Is the battery fully charged (>13.5vdc)?
Is there a safety switch on the clutch lever and/or side stand? If so, insure that it/they operate properly.
Are the spark plug wires going to the correct plugs?
Does each plug make a big, fat blue spark?
Is full voltage reaching the coils?
Is fuel reaching the carbs?
If the carbs sat for more than 3 or 4 weeks with fuel in them, they likely need a thorough cleaning.


If the easy stuff checks out (I'm sure someone will chime in with something I've forgotten), then on to the more challenging possibilities.

Is cylinder pressure up to spec?
Are valve clearances to spec?
Is cam timing to spec?

Getting an engine to fire only requires some compression, a relatively close air/fuel ratio and a well-timed spark. If any one of these is missing or grossly out of spec, there will be no love....

If you dismantled the timing advancer, you may have assembled it backwards.

If you did, it will backfire when you try and start it.

I replaced the all the gaskets. The timing was done spec to the manual.
Battery is charged
Kill switch is on
No safety switch
Spark plug wires all correct (and they all have a blue spark when i test them)
The spark plugs were wet with fuel when I pulled them out and fuel is getting to the carbs
Carbs only sat for 3 days
Cam timing is correct
And I did not take apart the timing advancer

Voltage with coils, valve clearance and Cylinder pressure- Have not checked. When I push the starter button, it rotates and everything seems to be working, but just not firing.

Choke lever is being applied?

yes, the choke lever is up

1) Check compression

2) Check spark plugs to verify spark

3) are spark plugs wet with fuel or dry?

4) Is the fuel tank petcock working? Some have to be in prime position to get fuel to start.


When you say:

I replaced the all the gaskets.

Do you mean you tore the engine all the way down to the crank and split the cases?

Or did you just do the top end?

Just the top end.
The fuel petcock is working and flowing.
Spark plugs are wet, and each one has a blue spark.

Compression- How do I check this?


Thank you all for the help in troubleshooting so far!

jordan23 wrote: Just the top end.
The fuel petcock is working and flowing.
Spark plugs are wet, and each one has a blue spark.

Compression- How do I check this?


Thank you all for the help in troubleshooting so far!

You can get a cheap compression gauge for maybe $12. Pep Boys used to rent them out.

You screw it into the spark plug hole, open the throttle and spin the starter.

I would also re check the valve timing.

Do you have a factory service manual?

I do have the service manual. I will pick up a gauge tomorrow and check it out, we shall see then. I checked the timing over and over for correctness.