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John Deere 185 lawn tractor backfires


2ndgencamaro's Avatar
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Join Date: Dec 2008
Posts: 118
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12-07-08, 02:28 PM   #1  
John Deere 185 lawn tractor backfires

Greetings,

This is my first post. I have a JD185 lawn tractor that is around 20 years old. It runs fine and has good power - other than puffing some smoke when if first starts. The problem is when I go to shut it off the mower. After completing cutting my lawn, I typically disengage the blades, throttle back the engine and drive at a slower speed back to my garage. Around 80 to 90 percent of the times when I shut the mower off, I get a single, loud exhaust backfire a moment after the engine stops running. I cannot con myself into thinking this is no big deal and would like to correct the problem for next spring when the mower is once again needed.

Any ideas on where to start?

Whoops - it is a Kawasaki FC540V - BS00 engine

Steve

 
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30yearTech's Avatar
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Join Date: Oct 2006
Posts: 1,176
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12-07-08, 03:22 PM   #2  
Believe it or not, it's no big deal. Except of course for the mild coronary experienced by the big bang.

What happens is the muffler has gotten very hot from your mowing session. When you shut the engine off, the spark plugs are no longer getting any spark but the engine continues to spin and draw fuel into the cylinder and then out into the muffler. If enough unburned fuel collects in the muffler and it's hot enough to ignite the fuel you get the big bang. To reduce this possibility, try lowering the engine to an idle speed and run it like this for about a minute before you turn the key off. Hopefully this will allow the muffler to cool enough that you don't experience the after fire (bang). Another solution (one that is used on many newer engines) is an after fire solenoid valve installed on the carburetor, there may be one available for yours. These solenoids stop the flow of fuel through the carburetor, when the key is turned off. This pretty much eliminates the after fire.

 
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