HELP - 6x4 Backfiring and No Start

[afavia]

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.
 

[David G]

Your timing is off, remember there are two TDC's.

When did it run last?
 

[afavia]

I am starting to think the timing is off as well. However I can believe the cam gear has any problems as the valves are operating as intended. Yes, I rotated to TDC 2x and set gaps on valves each time. What else could be throwing the timing off? I checked TDC on the flywheel and confirmed with a screwdriver in the plug hole to verify that the flywheel was not off.
 

[David G]

I would "assume" that valve timing is good based on your compression numbers. I would leave the fuel side alone for now. If multiple cylinder are you sure plug wires are not crossed?
 

[Dan in Ohio]

Your gator started getting the steel cam gear starting with this engine and serial number in Feb of 1998, FD620D-ES11 – Beginning serial 152490 – John Deere Model 6×4 Gator, if you still have the plastic cam gear that is where I am putting my money.
 

[jd man wis]

I also would say that the key in the flywheel and crank are sheared and throwed the timing off that where I would check.
 

[gbs]

neighbor had the same problem with a 14 hp briggs, he said when he was trying to start it his mother who lives next door called to find out what all the shooting was about, found out it had sheared the flywheel key was his problem, unlike the point type ignition an electronic ignition will still fire with the key sheared.
 

[afavia]

I went to oreilys and rented two (2) jaw pullers, however the 1st one (5-ton) was too small for the flywheel, and the 2nd one (7-ton), the metal 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?
 

[K Effective]

Flywheel is just taper fit to the shaft. A pry bar can take up the small amount of thrust in the crankshaft, then tap on the crank end with a brass hammer, or I have seen an air hammer used. The flywheel should pop right off, as long as there is just a little space for the crank to move away from the seat. Try to get the pry force as close to the center as possible.

If you can clean the end of the crank really well, you might be able to see the keyway cut in it and compare to the keyway in the flywheel, but not always.
 

[afavia]

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?