750 kawi can't get it to run on 2 cylinders

[maxsimoneau]

Hi, I bought a blown kawasaki 750 small pin motor. I rebuilt it with an used oem crank and brand new top end, milled head, small cylinder/case porting and lightweight flywheel.

Put that bitch in my ski and i can only get it to run on the PTO cylinder..

- has 180 psi compression on both holes.
- fuel is getting in both cylinder.
- reedvalves are OK.
- makes good spark with both spark plug wire.

Even when I pour gas in the MAG cylinder there is no explosion at all. But plug is sparking, compression is good , and it is getting air.

I thought maybe the timing is way off ?
Maybe it makes the spark when the MAG piston is going at BDC instead at TDC ? So gas is not igniting because there is no compression in the cylinder when the spark is produced?

I tried another complete ebox. Same problem.
Tried another stator . Same problem.
Tried interchanging the pickup coil wires( the blue and green ) but still wont run on the MAG cylinder.

BTW i made a deutsch connector to connect the stator and ebox because the connectors were chopped.

Crank seal Does not seem to leak.

What do you guys think ?
Last thing that needs to be checked is if the flywheel slipped on the crank, but need to pull the motor to check that. And it would be strange that it slipped enough to make the mag cylinder not ignite but the pto cylinder still ignite.

Do someone have an idea of what could cause this ? Could I missmatch a wire from the stator to the ebox while doing my deutsch connector? I put the green with green
Red with red
Black with blac etc..
Only wire that is not same color is purple in the stator to yellow in the ebox...

Thanks

 

[DylanS]

I’d suspect weak spark that isn’t jumping the gap under compression. You could also try a timing light to see what degree you’re firing at.
Someone more familiar with the kawi 750 would need to chime in on the ebox wiring

 

[kswiatk]

Buy an spark gap tester. Check that both plugs fire more than a half inch. Single carb or dual carb?

 

[maxsimoneau]

Thanks for the inputs.
It is a single carb sbn 46

 

[Scorn800]

Sounds like a bad coil to me. Compression is blowing weak spark out

 

[maxsimoneau]

Sounds like a bad coil to me. Compression is blowing weak spark out

I tried another complete other ebox with the coil and cdi

 

[WFO Speedracer]

What happens when you swap spark plug wires from one cylinder to the other ?

 

[Scorn800]

I tried another complete other ebox with the coil and cdi

Your stator could be going than, do you have a extra stator to swap out

 

[sturat]

Stator. Weak spark under load and 750 stators, when failing, will work for about 10-20 minutes, heat up, and then quit. They are the main weak point of that system.

cdi's typically when they fail, that's it. They don't *start* to go out, they just stop working Entirely. Usually one spark on hitting the start button and then none after that.

 

[Scorn800]

I've used 750 electrics for years and it's usually a coil or stator going bad when you run 1 on cylinder
What kind of light weight flywheel are you using?
Does it have 2 lobes or 4?

 

[SUPERJET-113]

Yeah, the early years 92-94' 750 stators were especially bad for "heat soak".

 

[maxsimoneau]

What happens when you swap spark plug wires from one cylinder to the other ?

No change at all. Motor will just run on the PTO cylinder even if I interchange spark plug wires.

I've used 750 electrics for years and it's usually a coil or stator going bad when you run 1 on cylinder
What kind of light weight flywheel are you using?
Does it have 2 lobes or 4?

It is a stock lightened flywheel. 2 lobes I think ?

 

[WFO Speedracer]

Have you tried an different spark plug in the front cylinder, Yeah , yeah I know , trust me I know, but I have seen NKG plugs be bad before right out of the box, by swapping the spark plug leads you have basically eliminated most of the rest of the ignition as a failure point.

 

[maxsimoneau]

Have you tried an different spark plug in the front cylinder, Yeah , yeah I know , trust me I know, but I have seen NKG plugs be bad before right out of the box, by swapping the spark plug leads you have basically eliminated most of the rest of the ignition as a failure point.

Yes . Tried 2 new spark plugs ahah
Will remove motor this week to check the flywheel.

 

[maxsimoneau]

Pulled the motor.
Unfortunatly , flywheel was on the right place on the crank with the key..
Also, the crank seal does not seems to be leaking...

 

[WFO Speedracer]

What are the engine and electronics out of, are they mismatched, I do recall that the ZXI electronics are different from everything else, if any of that stuff is from a ZXI you have to have the whole setup to make it work

 

[maxsimoneau]

What are the engine and electronics out of, are they mismatched, I do recall that the ZXI electronics are different from everything else, if any of that stuff is from a ZXI you have to have the whole setup to make it work

will try to verify that. flywheel/stator came with the motor (small pin) , and the ebox I bought one from ebay and I believe it is from a bigpin .

Try a different Flywheel.

The Flywheel Magnets could be bad even if they look okay.

That one Lobe looks damaged...

View attachment 426903

Just bought another flywheel to try .

 

[maxsimoneau]

Problem solved.
It was the flywheel.

Thanks everyone

 

[WFO Speedracer]

Thanks for confirming so many people never post the resolution to the problem.

 

[sturat]

Thanks for confirming so many people never post the resolution to the problem.

Oh licorice off. Usually when you swap out 2 different stators you would be looking at the flywheel too since you're in there.