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Deere lawn tractor L120 threw a rod


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06-07-10, 12:39 PM   #1  
Deere lawn tractor L120 threw a rod

John Deere L120 lawn tractor with a 20 HP B&S Intek 406777-0139 E1 code 010521G

I started mowing, then after a minute I heard something metalic snap. It wasn't loud but I did hear it.
The machine was still running fine until a minute later it lost significant power and was about to die.
I disengaged the PTO and it kept running but just at a high idle when in the full throttle position,
and popping alot. Pulled the spark plugs and # 1 cylinder plug was wet from gas, #2 was dry. Ended up I threw a rod on#2 ?????
(low on oil and I forgot to check it)
Replaced the one broken rod after cleaning up the crank. and new head gaskets for both cylinders. Started it up and it runs exactly the same, sputters, lots of blowback through the carb. #1 plug still get wet, only a fast idle, getting spark thru both new plugs. Adjusted the valves to .05 and compression reads 155#@#1---160#@#2
Engine only has 140 hrs. on it so I left the old rings on. Did not remove the valves. Cleaned the carb. but only lightly, it seemed pretty clean.
Any help will be appreciated.

 
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06-08-10, 12:56 AM   #2  
Sounds like a carb problem to me. Does applying partial choke help?


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06-08-10, 02:35 AM   #3  
No it doesn't. The choke works as it should for the cold start but once it warms up, applying the choke makes it run worse like one would expect. During my cleaning of the carb. I didn't have that special reverse torx socket needed to seperate the unit so part of it didn't get cleaned. I'll get a socket & redo it.

 
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06-08-10, 10:52 AM   #4  
you meant .005 on the valves I hope?

 
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06-08-10, 01:39 PM   #5  
you meant .005 on the valves I hope?

Yes

 
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06-12-10, 10:30 AM   #6  
Got the carb. apart, let it soak in parts cleaner for a day, followed by choke spray and compressed air. Reinstalled it and it's running the same. Lousy. Don't know which way to go. Thinking maybe a new carb. or pulling the head on the one cylinder and checking the intake valve & guide. But it has great compression? Any ideas?
Thanks

 
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06-13-10, 12:10 AM   #7  
Do both valves open and close the same amount on both cylinders? I have seen cam shafts go bad on these from low oil levels. This would cause your problem. You can tell by seeing which valve barely opens (if a lobe on the cam is wiped, that valve will not open far).


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06-14-10, 10:01 AM   #8  
Cheese, I don't know weather this is significant or not. I measured the distance the valves moved off their seats, here are the results:

#1 cylinder: intake 10/32"-----exhaust 17/32"
#2 cylinder: intake 6/32"-----exhaust 11/32"

As you can see, there is about 1/8" difference between the two cylinders. This is also noticable in the the valve lash adjustment screw. It has about 1/8" more thread exposed above the lock nut on #2. I double checked the valve lash before any measurements were taken.
Does all of this mean anything?

 
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06-15-10, 01:07 AM   #9  
Yes, it means either the valves are misadjusted, or the cam is worn.


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06-29-10, 11:57 AM   #10  
Well I think I found the problem



All bent to he_ _.



But this has revealed another problem





It doesn't leak as the crack doesn't go all the way through but it is on the flywheel side of the engine....as are both cylinders.... does this mean trash the engine or do I pay the $132.00 Deere wants for a cam, install it, and hope for the best?

Thanks for your help!

 
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07-06-10, 12:00 AM   #11  
I'd be inclined to put a cam in it if it were mine. You can probably pick one up much cheaper on ebay.


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07-06-10, 03:31 AM   #12  
Posted By: cheese You can probably pick one up much cheaper on ebay.
I'd do that in an instant if I knew what to search for other than the JD part #.
When I went to purchase the rod, all briggs manuals (for this engine & date) say you had to buy a new crank and 2 rods. So I go to deere and they tell me I have to use deere parts and they sell me the single rod. It was made by briggs, in their box, but deere's part#.
Anyway, I've looked up the cam and sure enough it's a deere part #



The on-line manual from the various small engine suppliers all show one part#. I've downloaded the parts manual from Briggs site and it say because of the date of my engine I have to get a new short block.
So you can see my confusion. I'm forced to use deere at twice the price of course.

 
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07-06-10, 04:25 AM   #13  
engine No. 9

I have a Kawasaki engine in my yard right now that runs great, sitting in a frozen john deere tractor. I don't see anything wrong with your cam, it will make a great convo piece. Part out the engine to help pay for a new one. Don't buy the new cam, I don't think it will work. But it looks like some people here think it will.

 
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07-06-10, 07:27 AM   #14  
I wonder if Briggs knows that the cam failure is due to a problem with the block which they fixed in 03 and that's why they direct you to a shortblock if the cam has failed in a pre-03 engine?
I have a friend who bought a Deere but don't remember how long ago and he had the engine replaced under warranty or recall not long after buying it.

 
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07-08-10, 01:26 AM   #15  
I believe this cam is bent because the engine threw a rod, and the remains of the rod came around and smacked the stew out of it before the engine came to rest.

790562 is the part number for the cam... it should be around $85.


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07-08-10, 04:57 PM   #16  
Posted By: cheese I believe this cam is bent because the engine threw a rod, and the remains of the rod came around and smacked the stew out of it before the engine came to rest.

790562 is the part number for the cam... it should be around $85.
Except on the IPL briggs gives that part number for the cam only for engines made after code date 03something and say shortblock if code date is prior

 
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