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Discussion Starter #1
Hello I am new to this forum and looking for some assistance. I have a 2010 HPX with a Kawasaki vtwin engine. The machine starts fine and runs great until gas is applied then it spits and sputters and sometimes it will take off. Other times it seems to be running on only 1 cylinder. Here is a list of items I have done. Gator has 1743 hrs

Fuel pump flow test
Changed fuel filter
Changed oil made sure it was not overfull
Drained gas tank then added 93 octane
Checked valve clearance. In spec
Cleaned carb. Carb looked very good for most part but did have a lot of carbon. Main jets were 57 air adjustment screws set at 2 1/2 turns each. I am slightly above sea level.
Removed plugs. A lot of carbon put new plugs in BPR2ES
Spark arrestor removed.
Ran engine with out air intake -no change
Replaced one coil - my thought was it was loosing a cylinder. I could not find a test for this in the service manual. -no changed swapped the other two coils no change

Here are my questions
1. Has anyone had a igniter moduale failure on these? This is the first item before the coils on the wire diagram
2. My carbon problems, has anyone adjusted the carb to lean it out a little with the two adjustment screws on top? How about a hotter spark plug?
3. A thought I had was the exhaust is plugged robbing power but that may not explain the mis fire.
4. On my carb the parts manual shows two pilot jets on outside of either carb. Mine did not have those. Are there different carbs for different gas machines?

Thanks for any help.
 

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Discussion Starter #2
A follow up here. I disconnected the fuel shut off solenoid in the carb and the machine seemed to run better but still had a slight mis under exceleration. (93 octaine). When I hooked the solenoid back up the engine would idle but misses completely throughout exceleration. I tested the wiring and it has 12v at solenoid when key is turned. I also tested the solenoid according to the service manual and it tests good. This machine had its fuel shutoff solenoid replaced (170$) about 400 hrs ago.

When the 93 ran out I filled up with 87. With the solenoid disconnected as before the machine runs very poorly again does not idle well and misses under exceleration. Connect the solenoid and idles perfect but misses under exceleratiin again.

Does octane make that much difference in these motors? States 91 on valve cover but book states 87.

Any help diagnosing would be appreciated.
 

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I'm not that familiar with this machine, but I'll throw these out there in the event they are relevant to your machine.

1. Did you check the spark plug wires by measuring the resistance in each one (ohms)? Also check to make certain the wire insulation is sound and not shorting along it's path. Sometimes it helps to test this at night, so the sparks are easier to see.
2. Did you do a compression check? Report finding if so.
3. Did you check float level to make certain it isn't too high, float sticking, saturated with fuel, etc? Could also have a leaking needle/seat.
4. Did you actually take the carb apart and verify all passages are clear/clean without obstructions?

Do you have a spark tester or a timing light? I've used both to see if the miss is fuel or electrical related. The strobe action of the light will be obvious when there is no spark.
 

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Personally I would drain the 87 octane ( presumably with ethanol) and refill with 91 octane (without ethanol) also add a fuel additive such as SeaFoam or Mechanic in a Bottle with the fresh fuel.

You may have introduced some bad gas in the system when you added the 87 octane ?

FFIW I never run any ethanol in my Gator or outdoor equipment.
 

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Discussion Starter #6
Update here. Sorry it took me so long to update this thread. I ordered new carb gasket kit which included intake gaskets and carb gaskets and the plastic spacer plate. I also replaced all gaskets in the carb and the jets in carb but saved the old ones as they looked fine (37.5 pilot and 75 main). I set the idle mixture screws at 2 turns out at first then checked the plugs after few hours then turned the rear out another 1/2 turn and the front out 1/4 turn. Then I adjusted the idle again.

The gasket material was very dried and I am assuming it was sucking air in at some point making the engine stumble. It has been running great now for about 70hrs. Still is cold blooded upon startup however, the choke helps this but nobody uses it for some reason.
 

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Thanks for reporting back what you found.

Hope it continues to run well for you!
 

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Discussion Starter #8
The HPX is now up to 1900 hrs and still running well. What I have found is that the Kawasaki engine seems to be very finicky with any slight air leaks in the intake gasket area. These are sometimes hard to spot as in a dried gasket. I have a 04 Kawasaki FE400 single cylinder engine in a utility cart that has the same stumble as this gator did. Hopefully the same repair will fix that one as well.
 

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Thanks for the follow up after several months of use.

It's important to close these threads like you did with long term results. There are too many threads in this forum where the OP asks for help only never to be heard from again. The quality of post detail and follow up will help others for years to come, assuming they take the time to search.

It's also a good idea to check flange flatness (gasket surface) and adjust if needed before reassembly.

Hope your success continues.
 

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Discussion Starter #11 (Edited)
Well at 2321 hrs now and back to a misfire under load only when hot. The miss is very random like a bad spark plug and then it clears itself up. Can not figure out which cyl is doing it because it misses then clears itself up when the throttle is either applied or let off. Things I have done recently.
  • Changed oil and filter with new fuel filter
  • New fuel pump as the old one was pumping air bubbles some times. I could see them in the filter. Ran it for about 2 hrs after that and this problem developed.
  • Changed the plugs with new ones BPR2es.
  • Coil test primary resistance is .2 secondary resistance on both and primary 11910 on the rear and 12300 on the front. FSM states 12000 primary and .2 secondary
  • Compression is 185 WOT on the rear and 190WOT on the front cyl which is similar to my last readings a few years ago.
  • Checked the fuel shut off solenoid for 12 volts and I can hear it moving when the key is turned.
  • Pulled line going into the tank and checked screen for clogs
  • Replaced line from tank to pump when fuel pump was changed as it had a nick in it.
  • Sprayed carb cleaner around the gaskets that were leaking last time to see if the throttle changes at all and it did not. Checked all bolts for tightness
  • Changed air filter and checked air flow is clear
  • Checked battery voltage 12.6 at rest
  • Changed negative battery cable as has slight wear cables tight. Cleaned contacts
  • Checked ignition switch and swapped it with a different one
The gator did only have a little use over the winter with stabil added to gas. About 4 months on one tank.

Any advise on diagnostics is welcome.
 

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Inspect plug wires and boots for possible burn through or other potential leak paths for the spark to jump. Its also best practice to use dielectric grease inside the boot. Sometimes testing under darkness, spark leaks can be seen.

Fresh fuel is also advisable to rule out it as a possible cause.
 
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Discussion Starter #13
Added fresh fuel and checked spark plug wires for arching in the dark this morning. One thing to note is the back spark plug is more lean than front spark plug so I richened up the carb slightly on the rear to try to keep them similar. Did not seem to change anything. There is not any fuel deposits on the plugs. The skip is not always there which makes it hard to figure out. One thing I did notice is going up a hill with about 1/4 to 1/3 throttle it skips for maybe 5 seconds or so then clears up if the throttle is moved. Also I can replicate the skip if I hold the brake and give it 1/4 to 1/3 throttle in high range. Possible the gaskets have failed again?
 

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Vacuum leaks are always a possibility.

Carb adjustment. The adjustment screw is typically for low speed or idle and the high speed is controlled by a jet and air bleed of fixed size. Not certain if the idle mixture screw is having much impact on AF ratios at the higher rpms. Then again I’m talking generalities and lack knowledge on this specific carb.

Adding fresh fuel to contaminated doesn’t really do anything. Best to drain tank of all fuel and then add fresh. Maybe this is what you implied.

I’ve used inductive timing lights to pin point ignition issues by correlating misfires to a break in light pulses. Testing each cylinder could at least pin point the suspect cylinder. Of course an oscilloscope would be a better tool but sometimes your limited to the tools at hand.
 
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