John Deere 14sb Backfiring

papagrandeMarch 28, 2008

John Deere 14SB mower backfires -- it was purchased "as is" although recently tuned up. Any ideas why it backfires?

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Timing sounds off.

    Bookmark   March 29, 2008 at 12:02AM
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Some people describe 'backfire' wrong, so could you describe a little more what you mean 'backfire' ?

    Bookmark   March 29, 2008 at 12:33AM
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Hi giventake,
It starts easily but sounds like it is running rough -- it belongs to my son in law, who just got a "good deal" on it. My brother suspects either a bent crankshaft, carburetor issues, or timing.

My knowledge of lawnmowers is based on ~30 year old technology. Although it sounds like a timing issue i have no idea how to adjust that in this newer model.

Is it a capacitor? is it a bent crankshaft? Is it a loose carburetor? dunno....

I appreciate your suggestions.

    Bookmark   March 29, 2008 at 12:44AM
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Lots of things could cause rough running, from a clogged air filter, to s clogged exhaust. Think of a engine as pump, and complicated :) anyways check all the basic deals air filter spark plug carb adjustment, dirty fuel/gas clogged gas filter, it gets involved, but guessing is silly. Do the prognosis with the basics of what makes a engine work properly.

    Bookmark   March 29, 2008 at 1:11AM
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Yep, that makes sense to check all the basics. Will do that. Also heard that a bent crankshaft could be the cause .... I'll check that last :)

    Bookmark   March 29, 2008 at 11:18AM
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If it is popping back through the carb, but starts easily- first I would do is replace the spark plug- then inspect the flywheel key. The rest of the ignition timing is done by the igniter which is the little rectangular piece w/ 1 terminal mounted on the side of the engine. That is provided the tune up guy didn't do something whacked with the armature air gap. You would think that if valve clearance/ sticking issues existed that it would be a hard starter.

    Bookmark   March 29, 2008 at 12:12PM
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Thanks tomplum -- great info. I'll have a look at those items today.

Glad i found this forum and I appreciate the advice from all.

    Bookmark   March 29, 2008 at 12:20PM
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lawnmowerdan(ne fla)

the choke is mostlikely stuck on-happens often on these-poor desighn-otherwise fine machine

    Bookmark   March 29, 2008 at 1:12PM
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Hi, I just saw this post. I don't know if my problem is identical, but its driving me crazy.

I have an older 14sb (green) It starts first pull runs fine for a few minutes (3-5) then dies down and almost out, slight backfires through carb.

I have done the following.

removed fuel tank, screen and cleaned. I have replaced fuel line and added filter. Replaced plug and air filter. I have rebuild the carb 2 times.

I have replaced the carb with one found on ebay.

I have changed the coil with one purchased on ebay. Unfortunately the wrong model coil. I tried to make it work and it hardly ran.

My question is .. what is this little square box on the side connected to the coil? I thought it was a condenser. All it says is Japan on it. Can this be the problem.

    Bookmark   May 29, 2008 at 5:47PM
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Hello. I am having the same problem as described here and hoped someone could offer a solution.

I've replaced the coil with a used on that seems to work and just bought a new carb and am still having the same problem. When I go to start, it takes at least six pulls to get it interested in starting. Then, it just barely chugs along but is not really started. In other words, there's no way I could engage the blade and mow anything with it ch-ch-chugging the way it does.

I have a new filter, clean & fresh fuel, and removed the air filter for the sake of troubleshooting...still nothing. Also, I have the 14sb model that does not have an igniter.

Any help would be greatly appreciated.

    Bookmark   April 26, 2009 at 5:03PM
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Maybe there are deposits on the valve stems that are holding things up. Try helping it along with a burst of carb spray every few seconds for a spell. I assume that you have verified the choke is closing on cold starts and opens back up again when you bring the control back.

    Bookmark   April 27, 2009 at 12:28AM
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I recently had this very same issue with the L130 with the OHV Kohler Engine. What I found was four loose shoulder bolts. I would suggest to anyone having this issue is: remove the valve covers, ensure that the connecting rods are straight and in the proper position, make any necessary corrections, and snug up the four outer most bolts that secure the rocker arms. (a dab of Loctite  or similar product is not a bad idea either)

    Bookmark   May 8, 2010 at 3:35PM
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backman01(nc pa)


    Bookmark   May 9, 2010 at 9:47PM
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My JD 334 starts fine and runs well until it gets a load (engaging the mower deck and relatively tall grass), then sputters and backfires. It did it raraley intilatty, now much more common under minor loads/work. Any suggestions?

    Bookmark   April 18, 2011 at 8:46AM
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