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I have a Kawasaki FC420V in a John Deere LX182 that won't start. After 4 or 5 cranking attempts it will ignite the fuel in the muffler with a loud bang. I have replaced the coil, ignition module, spark plug, flywheel/crank key. I also checked the valve lash and compression. Compression was 80+ PSI. Spark tester shows spark. Using ether makes little difference. This happened a few times in the past and I was able to restart by boosting with a car battery, but this time it doesn't help. Sounds like it some kind of timing issue. Does anyone have an idea what to try next.

Harold Wilson

Hi. This is a bit of a hunch, but I had a similar problem with one of my Kawasaki engines. How fast is it turning over? It could just be a bad battery or worn starter drawing too hard and not spinning fast enough. If the battery is far enough gone even jumping it won't send enough "juice" to the starter to spin the engine fast enough to fire.

It's always seemed to turn over slowly to me but hasn't changed recently. Guess I'll pull the starter and see. There is a test in the manual for the starter but you need a way to measure the free spinning starter RPM's.

I'd try to jump it directly from a good battery to the terminals first, eliminating your mower battery, and see if that works.

I tried substituting my tractor battery with no success. Then I remembered this is a metric engine. I pulled the flywheel and mic'd the key. The original key mic's 0.197". The replacement from the hardware store mic's at 0.187". Checking the other measurements the key looks to be a 5 X 6.5 x 15.7 mm key. Guess I'll order a metric key. I don't find my exact model listed its a FC420V-AS10. I find listings for AS09 & AS12 and they are both the same key.

I attached a photo of the old key. Is 0.010" difference enough to get the timing off enough to not start?

Do a leakdown test of each cyclinder. Compression seems a little low. Might not be firing under compression very good

I picked up an OEM flywheel key at the John Deere dealer today and installed it. Still doesn't start. Today with ether I could get a couple backfires from the carb which it hasn't done before. Took the fuel hose loose and the pump puts out plenty of volume. Also checked the carb bowl, it has fuel in it. Looked at the spark plug and it wasn't wet like I would expect.

I did try my homemade leak down tester (air tee'd into a compression tester) earlier. At 40 PSI I could only detect leakage by the rings. I think I need to re-do the compression test with adding oil thru the spark plug hole.

May have to put on hold a few days, It's supposed to be dry here & I need to do some gardening and mowing. I don't use this one to mow anymore, just to pull a trailer and a sprayer.

Never liked using either I preffer to use caarb cleaner, much easier on the engine & does not diesel in a mower engine.
So give a shot of fluid down the plug hole & crank the engine.
Engine fires = valves are sealing & timing is good.
do the same down the carb throat.
Engine does not fire, valve timing is bad
engine does fire , = fuel problem.

You never told us why it stopped running in the first place and this is important cause you may have skipped or broken a tooth on the cam shaft.

It didn't stop on it's own. I shut it off. Then when I went to restart it a few min later it wouldn't restart. This actually happened a couple times before when I had a weak battery in it, then when I towed it back to the shop it restarted with a boost. This last time it has a new battery and also will not restart with a boost.

I'll try shooting carb cleaner into the spark plug hole tomorrow.

I shot some carb cleaner into the spark plug hole, replaced the spark plug & cranked. What I got was a loud bang & blaze from the muffler. Did this a second time with the same results. I then put a shot of carb cleaner into the carb throat. I got 2 or 3 mild backfires thru the carb. Tried it a second time and got a laud bang & fire from the muffler & then 2 or 3 backfires thru the carb.

Whip the rocker cover off.
You have a stuck valve, burned valve or the valve timing is off.
verify the valve timing by putting a stick in the spark plug hole and rotating the engine 2 full revolutions

Took off the rocker cover, Spinning the engine over both valves appear to move up and down about the same amount.

At top dead center the flywheel magnet is about centered on the second leg of the coil.

At top dead center both valves appear to be seated, there's lash in the rocker arms.
Exhaust valve starts to open about 3/8 rotation, full open 3/4 rotation, closed about 1 full rotation.
Intake valve starts to open about 1 1/8 rotation, full open about 1 3/8 rotation, close about 1 3/4 rotations.

Decided to recheck compression, 105 PSI (must have not gotten it tight first time last week).
Added about 50 PSI air thru the compression tester with piston at TDC on compression stroke. Can hear a very slight leak in the crankcase and exhaust valve, none in the intake.

It seems to me that the valves are not adjusted correctly.........

Harold41 said:

Took off the rocker cover, Spinning the engine over both valves appear to move up and down about the same amount.

At top dead center the flywheel magnet is about centered on the second leg of the coil.

At top dead center both valves appear to be seated, there's lash in the rocker arms.
Exhaust valve starts to open about 3/8 rotation, full open 3/4 rotation, closed about 1 full rotation.
Intake valve starts to open about 1 1/8 rotation, full open about 1 3/8 rotation, close about 1 3/4 rotations.

Decided to recheck compression, 105 PSI (must have not gotten it tight first time last week).
Added about 50 PSI air thru the compression tester with piston at TDC on compression stroke. Can hear a very slight leak in the crankcase and exhaust valve, none in the intake.

Click to expand...

We need you to translate that to piston positions.
Exhaust should open around bottom of the stroke and remain open till just past top of the stroke.
Just before the exhaust valve closes the inlet should open and remain open till the piston gets almost to the bottom then close.
On the following up stroke the inlet should open a tiny amount ( decompression ) and this can be anywhere from about 1/2 way up to almost all the way up then close again.
The inlet valve should be closed before the magnet is between the legs of the coil.
DEpending upon the chip the actual firing can be anywhere from magnets between the legs or magnet just passing the 2nd leg.

The exhaust starts to open before the bottom of the stroke and closes at the top of the stroke.
The intake starts to open after the top of the stroke and closes well past the bottom of the stroke(about midway in the upstroke).
Decompression opens the exhaust valve a tiny amount immediately after the intake valve closes.
The intake valve is closed before the magnet gets to the coil.

I checked the valve lash a few days ago. Intake was OK, the exhaust required a very minor adjustment.