John Deere with Kawasaki FC420V

Trying to help my 80 year old uncle get his John Deere mower running again.
It has a Kawasaki FC420V engine.
It had a new coil two years ago.
No spark this Spring and we determined the ignitor was bad.
Ordered a new OEM igniter / module.
My uncle installed and he said it ran great for 1/2 hour or
less and he shut it off, and was never able to get it
started again.
It now "pops" in the carburetor and flames are visible in the
carb intake (with air cleaner off).
Spark at plug appears to be good.
New spark plug was tried.
Flywheel key looks good.
It has 118 psi compression, so it can't be an intake valve
"hung up".
Ideas appreciated!
Tom

Google: "K&T Parts House Kawasaki Engine Repair Manuals" , click on FC420V 4 down, download at bottom left of screen, see troubleshooting section page 8.




























Google: Kawasaki mower engine repair manuals, click on " K & T PARTS HOUSE REPAIR MANUALS", click on FC420V 4 down, download at bottom left of screen, see troubleshooting section page 8.

Thanks! Manual downloaded, and will start "looking"!

Went thru the manual last night and nothing really "popped out" at
me regarding what may be the problem with this mower popping
and spitting fire out the carb intake, and not starting.
At $70 a whack for a new igniter / module I hesitate to have
my uncle buy another one just to try it.
I did an ohm test on the original module and got the same readings
when test leads were "swapped", and therefore was determined bad.
New module / igniter has different readings.
My ohm meter is "auto sensing" and isn't coming up with the
spec readings. The manual did mention to use the Kawasaki approved
test meter or you may get the wrong readings :-(
I'd find it hard to believe the valve timing could have jumped.
I'm still open to ideas. Thanks, Tom

Ok so Lets think this through. Gas fires in the cylinder. Fire should only be there. What stops the fire from entering or exiting the cylinder? Valves that are timed correctly so they open and close at the correct time so burning gas does not go into the intake manifold or exhaust manifold when it is not supposed to. So if fire is in the intake manifold either some one has places a spark plug in there or the valve is not closing at the correct time or completely. So what could cause this? Timing off, in correct valve lash. So I would check the valve lash and the shear pin. Not just look at it but remove it and inspect.

If it is truly an electronic module it cannot be trouble shot? The manual tells you how? Next , isn't 118 lbs compression a little low? Taken hot or cold, with carb butterfly open? Just comments. Valve timing doesn't jump , it changes slowly as lash changes. As cam contour turns round it picks up the lifter/valve later due to the increased lash (clearance).

Blaz & Motorman,
Thanks for your replies. I believe the manual said 70 psi was
minimum compression for these engines, if so, I would think
118 would be great. Agreed that it would be hard for gear driven valve timing
to change. I can't picture what could have happened to the valve
lash to cause the intake valve to be open at TDC on compression
stroke and still have good compression.
My uncle was a mechanic a good deal of his 80 years, but I did
question him about the flywheel key, and he said he checked it
and it was "clean as a whistle". Next visit there I'll see if I can
convince him to pull the flywheel so I can see.
I will check the valve lash. It seem to crank over good, so I think
the exhaust lash with the compression release is working okay.
I'm guessing it's the igniter module, but hopefully the flywheel key!
Thanks for your help. Will try to report back if we find the problem!

QUOTE=BlazNT;231676]Ok so Lets think this through. Gas fires in the cylinder. Fire should only be there. What stops the fire from entering or exiting the cylinder? Valves that are timed correctly so they open and close at the correct time so burning gas does not go into the intake manifold or exhaust manifold when it is not supposed to. So if fire is in the intake manifold either some one has places a spark plug in there or the valve is not closing at the correct time or completely. So what could cause this? Timing off, in correct valve lash. So I would check the valve lash and the shear pin. Not just look at it but remove it and inspect.[/QUOTE]

A sticking exhaiust valve can cause blow back out the carb.
Pull off the rocker covers , check the heights of the valves, they all should be the same,
Watch the operation of the valves.
These engines tend to bend pushrods.

Thanks for your reply. I can't visualize how a sticking
exhaust valve can cause blowback thru the carb, but
will check the valve operation anyway.
Thanks!

bertsmobile1 said:

A sticking exhaiust valve can cause blow back out the carb.
Pull off the rocker covers , check the heights of the valves, they all should be the same,
Watch the operation of the valves.
These engines tend to bend pushrods.

Click to expand...

Because when the inlet opens there is still pressure inside the cylinder.