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Discussion Starter #1
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.
 

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When you say your oil is overfull what does that mean? Too much oil will bypass the rings and enter the top of the cylinder fouling things up
 

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Discussion Starter #3
The oil level is too high and thin. The plugs do not foul as the engine will not start. When starting attempt, backfiring occurs through intake and carb. If I pull the plugs after starting attempt, plugs are clean, but have fuel on them. Thanks Kbar for looking at this!
 

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I would check the ignition and valve timing. I had an engine that acted very much the same. The key on the crank holding the flywheel and magnet was slightly sheared. Stress that "slightly" May not have been sheared, just worn. Consider a .001 inch displacement at the key is magnified by the radius of the flywheel.

Please update us on what you eventually find as the solution.
 

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Could also be a bad spark plug wire.
 

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Discussion Starter #6
I rented a jaw puller for the flywheel and hope to get this removed tonight to check the woodriff key. I will also check the ignition coils and spark plug wires for cracking and loss. I will post updates tomorrow - thank you all for your thoughts on this issue.
 

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Know how to do a spark test?
 

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OP ... Verified he has spark ... #6 of first post. Now whether or not the spark is happening at the correct time of the piston stroke is TBD.
 

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Discussion Starter #9
I performed a spark test in (2) two different ways. I confirmed spark against the block with the plug, as well as using an in-line spark plug tool.
 

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To back fire through the carb, it must be firing with an intake valve open. Either timing is off, or valves not adjusted correct.
 

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Discussion Starter #11
I rented (2) two jaw pullers, however the 1st was too small, and the 2nd 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?
 

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When our 1800 Utility Vehicle does this it is always one of two things the battery or the solenoid that shuts off fuel at the carb. The first time I pulled my hair out similar to you.

I know what your thinking if the fuel is shut off it wouldn't backfire. So did I.

I know what your thinking it seems to spin over fine. Yep, just not quite fast enough so perhaps it could also be the starter, ground or loose cable. For me it has been the battery.
 
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I rented (2) two jaw pullers, however the 1st was too small, and the 2nd 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?
Are there threaded holes on the flywheel for a puller? A "crossbar" type puller you bolt to the bolt holes on the flywheel with a large center "pusher" bolt to "push" off the flywheel.
I would expect the bolt holes to be metric.
 

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Discussion Starter #14
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?
 

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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?
Thanks for posting back on your success getting the engine to run.

On page 29 of the doc Chuckv posted, it says to "remove the key" Your key is merely tight in the shaft. Did the flywheel slide easily back on the crank ? Perhaps there is enough movement to change the spark timing.
 

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I glad you have it running!
I was thinking valves too tight, a burnt intake valve/seat, or timing wrong. Maybe the carb to intake was leaking (sucking air) and making it too lean to run, but backfire???
 

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"Backfire" is not always a timing issue but it can be -- spark at the wrong time can ignite the mix prior to the intake valve closing and the engine will spit back through the carburetor. But a detonation noise can also occur when there is too high a mix of unburned fuel leaving the cylinder and igniting in the hot exhaust manifold, and while some describe this detonation as a backfire it really is a different set of circumstances.

Chuck
 
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