# John Deere Lt 133



## linbef (Sep 10, 2011)

*John Deere Lt 133 doesn't start just backfires*

I have a John Deere LT 133 riding mower, and have put all new part on it, but now it won't start. All it does is backfires. 
Has new starter, fuel pump, lines, cleaned carburetor, valves, piston, has new gas, and oil. Any thoughts on this??
It has a Kohler engine 13hp.


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## jrrdw (Jun 26, 2010)

Flywheel key or intake valve. Is this a over head valve engine?


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## kbowley (Sep 23, 2009)

Hi, Your Kohler Command is a great engine that has no particular weaknesses. Your engine uses hydraulic valve lifters. This leads me to believe that this is an area to investigate. But the first thing to check is the spark plug, simply replace it to eliminate it as a possible cause. Next inspect the wire going between the coil and plug to ensure it is not worn, cracked or otherwise damaged. If it is you can use some electrical tape as a temporary fix until a replacement coil is installed.

There are a number of potential problems with hydraulic lifters. Frequently, the valve-train will rattle loudly on start-up due to oil draining from the lifters when the vehicle is parked. This is not considered significant provided the noise disappears within a couple of minutes, typically it usually only lasts a second or two. A rattle that does not go away can indicate a blocked oil feed or that one or more of the lifters has collapsed due to wear and is no longer opening its valve fully. The affected lifter should be replaced in the latter situation.

In certain circumstances, a lifter can "pump up" and create negative valve clearance so that its valve cannot close. Typically this occurs in the most upper rpm range of an engine, and limits the engine's performance. Lifter pump-up is serious, as there may be interference of the valve with the piston or, burned valves may result. In all cases it is important to follow the manufacturer's recommendations for oil viscosity and quality. I strongly recommend Mobil One 10w30 be used in your Command.


I would pull the valve cover and ensure both valves are closing properly.


Secondly, as jrrdw offered, is the flywheel key way. To check the key way and ensure it is intact, first remove the top cooling shroud. Next you will remove the flywheel ( I am assuming you have a flywheel puller if you have disassembled the engine as you stated) with a puller and triple check the wood-ruff key to ensure both the flywheel and crankshaft are properly aligned. Since the ignition timing is controlled by the position of the magnets within the flywheel, they must be in correct alignment for the engine to run.


Write back and let us know how you are progressing.


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## WoodCarva (May 22, 2016)

I have a similar problem.

So late last summer my boys was riding around on the mower and it started to back fire through the carb. All of a sudden a really loud backfire killed it, and that was the last we hear from the JD. Plenty of gas, oil, and spark. i tried to put starter fluid in but it just backfired. I pulled the plug and placed my finger over the hole. there seemed to be some presser at lease. plug should be gapped .040" which it is. the seat safety switch works fine. I do not know what to do now.


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## kbowley (Sep 23, 2009)

More likely than not is that your flywheel keyway sheared causing the timing to be incorrect. 

Remove the valve cover and inspect the valve operation as well as the pushrods (simply pull the pushrods straight out from the engine to check for any bends) and then inspect the valve guides to see if one has slipped outward and is preventing the valve from opening.

Next, remove the spark plug and insert a small diameter screwdriver into the hole and turn the engine over by hand until the piston has traveled to the top...with the piston at top dead center, check the alignment of the ignition coil with the magnets on the flywheel. The magnets should be nearly past the coil when the piston is at top dead center.

If the valves are the issue, purchase a complete replacement head (about 150.00) and swap it out.


If the flywheel key has sheared (more likely than a valve issue) than use a flywheel puller and ensure the all remnants of the old, sheared key has been removed from the slots on both the crankshaft and flywheel...you can use a small screwdriver to knock the old one out of the slot(s). Visit you local small engine shop and get a replacement key and, using caution, re-install the flywheel.

Kevin,
Kevins Small Engine Service,
South Berwick ME. 03908


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