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Posts: 14
Reply with quote  #1 
My Predator keeps running after shutting off ignition.  It does it after it's hot, and will run for another 3 or 4 seconds after turning off the key.

Is this a symptom of running hot?   Or lean?
Or some other sort of issue Im not aware of?

Im thinking the carb needs cleaned as the (Im guessing) ethanol laced garbage they call fuel sat in the tank for a while this summer.   So if the pilot jet got a little varnished, I could see that causing it to run lean.  Lean = hot.   Hot = dieseling (aka run on)?

I searched and couldnt find anybody referencing any of those keywords, so didnt know if that was common.

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Posts: 945
Reply with quote  #2 
This has been known to happen with after market CDI as they have more capacitance and this may be just the drainging of the capacitor.
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Posts: 14
Reply with quote  #3 
Interesting.  I've never heard of that.  It could certainly be a possibility.

Googling the subject shows that it is also common with vehicles (non ATV or Predator specific) that are running hot.  It will do this as hot spots in the combustion chamber will cause detonation to continue to occur even w/out ignition.      It seems running lean is a common cause of that, although carbon buildup in the combustion chamber can cause it as well.
I think it's time for me to pull the carb and give it a good cleaning.   I have a feeling this ethanol crap gas has done a number on it.

Posts: 14
Reply with quote  #4 
Here's a little update.
I finally got around to pulling and opening up my carb. 
Shockingly, it was spotless inside.  When I say spotless, I literally mean I couldnt find a speck of dirt anywhere (except what looked like maybe a little crud in the accelerator pump?).
That worries me a bit, as I clearly cant blame a blocked idle jet or anything.
I did notice the original A/F adjuster plug is still in place, so this carb has never been adjusted.   I'll drill that out and at least have the option of adjusting it a little richer.

I have not put it back together yet (waiting for the rebuild to get here w/ new o-rings) , but once I do I'll post up if the same running conditions apply.  I decided to go ahead and soak the whole carb to get it good and clean.  Im also shortening the slide spring from the stock 4ish inches, and drilling out the vaccum ports on the slide.   And I'll check and adjust the valves before spring gets here.

If it does run the same, Im actually wondering if old/bad gas can cause something to run hot/lean?   Or if it just runs poorly?


Posts: 1,674
Reply with quote  #5 
Old cars on cheap gas used to do it.  It was called "Dieseling" or "engine run on".  Back in the 70's and early 80's theyd sometimes rune a few seconds after the key was turned off (they fixed the carbed vehicles in the late 70's by using a solenoid that speeded up the idle speed when the car was running and pretty much completely closed the throttle completely when the key was turned off).  However... I doubt that's your problem.  When they "ran on" they usually sounded like a can of marbles in the motor (gasoline makes lousy diesel and "explodes instead of expanding" when it ignites due to heat and pressure instead of spark). 
  I personally think its a CDI thing but if you want to test this, you could add a couple cups of the best gas you can find (most motorcycle shops sell racing gas) and see if the problem goes away.  If you still have it, then maybe check your idle speed and try swapping CDIs with someone. 

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