# Tecumseh 12 hp (ovxl120) help



## goatah (Oct 30, 2006)

Hi. I am a newb to this forum, and to fixing small engines, and was wondering if you guys would point me in the right direction. I have the above engine in an older riding mower which recently quit running. I pulled the rocker cover to find that the exhaust valve pushrod was no longer in its seat on the rocker arm. When I turn the crank by hand, the intake valve pushrod seems to work properly, but the exhaust pushrod doesn't even move. Bad lifter??? Where do I start? Thanks in advance.


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## 30yearTech (Sep 14, 2006)

Possibly just stuck. Make sure piston is at top dead center on the compression stroke and with a long puch lightly tap on the lifter to see if it will move and free up. Very important that you are on the compression stroke so cam lobe is away from the lifter, otherwise you may damage camshaft.


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## goatah (Oct 30, 2006)

The pushrod seems to be in too far to even reach its seat. I can grab it and move it in and out. Also, the exhaust valve moves when i manually compress the spring, but it doesn't come out as far as the intake valve. Maybe the exhaust valve is also stuck?


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## 30yearTech (Sep 14, 2006)

Ok, then perhaps the valve lash on the exhaust is just too loose and allowed the push rod to fall off the rocker arm assy., hold the pushrod down against the lifter and pull the starter rope or crank over the engine and see if the push rod moves in your hand. If it does, then reinstall and set the valve clearance on both valve and then check the operation of the valves.

Note: Turning the engine over will be easier with the spark plug removed, and will also need to be removed to set the valves as you will probably need to turn engine by hand to get to TDC.


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## goatah (Oct 30, 2006)

I can turn the engine over by hand pretty easily even with the spark plug still in place. So, I originally thought it was a stuck exhaust valve. Also, If the lifter was stuck, wouldn't the pushrod be stuck extended? Instead it is dropped in. I didn't pay much for this mower, and don't want to take it to a shop. Besides, I'm always up for a challenge, but I think I am in over my head. Any help is greatly appreciated!


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## 30yearTech (Sep 14, 2006)

Well I don't really know if the lifter is stuck. The valve spring is what pushes the rocker arm back and pushes down on the push rod and then the lifter. If the push rod fell off then the lifter would not go back down on its own it needs a little push. If it has been sitting for awhile it may just be stuck and need a little nudge to start working again. The valves on these solid lifter engines need periodic adjustments, they tend to get loose over a period of time, if they get loose enough then the push rod can fall off of the rock arm. If a valve gets stuck open that will also allow the push rod to fall off of the rocker arm. If it looks like one valve is in much further then the other then there could be a problem with the valve.


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## goatah (Oct 30, 2006)

30yeartech,

Thanks for the info! I'll do some messing around with it tonight to see if I can figure this thing out.


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## big ed (Jul 29, 2006)

i have seen this situation before and your engine may have swallowed a screw from your carb butterfly or some foreign matter you said the exhaust is not closing the same asthe intake which leads me to belive something may still be in between the valve and seat which would cause the pushrod to drop due to much clearence just a thought good luck


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## markymark63 (Apr 24, 2015)

*Exhaust Push Rod*

I am having the exact problem on my 12.5 hp Tech. Rocker arm fell off exhaust rod. Push not moving when I rotate the crank shaft. Let me know if you figure it out. I have a service manual for the engine but I am stumped.


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## 30yearTech (Sep 14, 2006)

If the push rod is not moving when the engine is rotated, then it could either have a stuck lifter, or the camshaft is damaged.


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## markymark63 (Apr 24, 2015)

Yea I was looking at a service manual, I think the spring connected to the cam broke or came loose.


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## markymark63 (Apr 24, 2015)

I figured that much out. I would appreciate any useful information.


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## markymark63 (Apr 24, 2015)

30yearTech said:


> If the push rod is not moving when the engine is rotated, then it could either have a stuck lifter, or the camshaft is damaged.


I figured that much out. Thanks for the no help.


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## Sir Thomas (Dec 7, 2013)

The only thing I can suggest is to break the whole thing down and rebuild, checking clearances, binding, spring strength. Clean and lubricate the whole assembly. It's probably got some build up that is restricting free movement of the rods. If one goes bad then the other will follow. Lot of work but I think it will be worth it.


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## markymark63 (Apr 24, 2015)

Yea I think I could rebuild it but I don't have the tools and I don't want to buy the tools because I was trying to sell it anyway.


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## Sir Thomas (Dec 7, 2013)

markymark63 said:


> Yea I think I could rebuild it but I don't have the tools and I don't want to buy the tools because I was trying to sell it anyway.


If you know what tools you need, check your local Auto Parts Store (Advance Auto, Auto Zone or NAPA). Most of them have Loaner tools. You pay for them. Use them and if you want to keep them, you don't take them back but if you don't want to keep them you do, and you'll get your money back.


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## markymark63 (Apr 24, 2015)

*Videos*

Anybody know of any how to videos on repairing a camshaft on a overhead valve. I have looked on youtube but can't find exactly what I need.


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## nbpt100 (Jun 1, 2015)

It may not exist. But take another look on You Tube on the Donnyboy73 channel. He has some of the better small engine videos and a wide selection. 
Otherwise you may have to make your own video.


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## markymark63 (Apr 24, 2015)

*Back fires*

Tecumseh 12.5hp - I adjusted the lifters, rebuilt the carburetor and all it does is back fires when I turn it over. Anybody got any ideas?


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## geogrubb (Jul 28, 2006)

markymark63 said:


> Tecumseh 12.5hp - I adjusted the lifters, rebuilt the carburetor and all it does is back fires when I turn it over. Anybody got any ideas?


Sounds like a sheared flywheel key, remove the flywheel and check that the key is not sheared, you must remove the flywheel because it can shear below the area that you can see. Have a good one. Geo


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## markymark63 (Apr 24, 2015)

I don't think it is the flywheel key. I tried turning the flywheel by hand while holding the crankshaft pulley. Could it be a stuck valve?


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## 30yearTech (Sep 14, 2006)

markymark63 said:


> I don't think it is the flywheel key. * I tried turning the flywheel by hand while holding the crankshaft pulley. *


What exactly did you determine with this test?? If you were expecting the flywheel to spin on the crankshaft if the key was sheared....you would be wrong. The ignition timing could be off and the flywheel would still be tight on the crankshaft. 

You might want to double check the valve lash as insufficient clearances could also cause a backfire.


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## markymark63 (Apr 24, 2015)

I have sheared pins before because I didn't tighten the flywheel nut enough. Believe me, I got the sucker tight, but I will check again. Thanx


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## 30yearTech (Sep 14, 2006)

Also make sure the spark plug gap is correct.


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