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.

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.

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?

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.

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!

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.

30yeartech,

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

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