HELP - 6x4 Backfiring and No Start

I purchased a 1998 JD 6x4 with Kawasaki FD620D Liquid Cooled engine that will not start and only backfires through the carb when starting attempt.

I have completed the following:
1. Compression tests show 175/180
2. Flywheel rotated to TDC on each cylinder and valves adjusted to 0.010
2a. I made sure of TDC with a screwdriver in the spark hole.
3. All push rods and rockers checked and confirmed ok.
4. Valves and rockers operate as should with starter motor, cam gear must be ok.
5. Spraying starting fluid in carb or directly in intake only can achieve a backfire through carb / intake
6. Spark / Fire tested and successful at each plug. Verified against block and with spark plug tool.
7. Fuel verified and confirmed at carb. Electric Fuel Pump.

Next Steps I am planning:
1. I ordered new spark plugs (NGK BMR2A)
2. I ordered a new carb
3. I will clean out the spark arrestor and muffler.
4. Planning on pulling the flywheel and checking woodriff key.

I am honestly stumped on this. I have good air, fuel and spark. I have tried with choke, air filter removed, carb covered with hand, spray, etc. Also, the oil is overfull and thin but clean and correctly colored. Possible fuel in gas tank from starting attempt too many times without firing?

Any help would be appreciated.

Do you know any history on this problem with that kawasaki?

It sounds like your timing is too early and the intake valve(s) is still open.

Valve clearance should be more like .004 than .010, but I don't think that is all your problem. While it is not uncommon for a valve guide to move and hold a valve open, I am thinking yours is a 2 cyl and it is not common for both sides to fail at the same time.

I am thinking this is a similar engine to the Lawn and garden versions in which it was common for the camshaft to shuck its gear teeth at about 600 hours. You may have to take the cover off and confirm that you do have an intact gear on the camshaft. (I remember just 3 teeth off a Briggs engine cam almost drove me nuts one time.)

I am also thinking that Most of those water cooled engines used a spark 'controller' and it was mounted low one side of the engine. I have had to swap in a known-good controller to eliminate it as the problem.

Thank you T.R.K.

1. If the cam gear is the issue, would the starter still operate the valves and have movement when starting is applied? Both sets of valves, rockers and push rods seem to operate fine with using the starter.

2. For the Spark Controller, do you mean the CDI or Ignitor? Like this: https://www.ebay.com/i/224174558101?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=224174558101&targetid=1098102009964&device=c&mktype=pla&googleloc=9019011&poi=&campaignid=11774045932&mkgroupid=117378450867&rlsatarget=pla-1098102009964&abcId=9300473&merchantid=6296724&gclid=Cj0KCQiArvX_BRCyARIsAKsnTxOeYLf8YGHpfKkXD16iCGJn6ObhTMgzrs0f_ObgPcosgf6bZpAkpaEaAoOiEALw_wcB

3. Is there anyway to test this component?

Hi, You are correct on the .010 valve clearance. Check the spark arrestor screen on the end of the tail pipe before checking the flywheel key.

Sorry about the valve clearance. Most if my experience is on the air-cooled Kawasaki engines. And I don't have any experience at all on the Mules.

We had a Wheel Horse with same engine in the shop that had somewhat similar symptoms. It would kinda run but backfired through the carb and had zero power. Ended up being what Kawasaki calls the "ignitor" which replaces points in the ignition system and controls timing.

I rented (2) two jaw pullers, however the 1st one (5 ton) was too small, and the 2nd one (7 ton) was too think to fit behind the flywheel and the block. Anyone have a trick to get the flywheel off without using a hammer and pry bar?

If the flywheel is not already drilled and tapped for a puller you will need to do it, that is the proper way to do it. I hope you didn't screw it up trying to use a 2-jaw!

I just googled it with your specific engine, and they don't mention using puller holes, but that would still be my preferred method. They show some good procedures and some bad ones, you will have to sort through them!

I was able to remove the flywheel with a harmonic puller. To my surprise the woodriff key is actually a part of the crank and not seperate? I cleaned everything up and took the opp. to replace the plugs and again re-seal the carb with new gaskets and gasket sealer. It fired up! I have no idea what I did to correct this issue, as nothing else was really improved or changed?