Mower motor issue

[deadeye]

So yesterday I'm mowing my sons yard (he lives about 4 long blocks from me) and the mower lost major power and almost choked out until I turned off the blades.  I though something may be in the belt etc but everything was free.  Started mower and same thing when I tried to engage the blades.  I drove it home and starting looking for the problem.  Discovered that one cylinder was not firing. Got spark, swapped plugs (they are old), sprayed starting fluid in cylinder, swapped coils, same problem.  I could leave one plug wire off and it seemed to run ok after putting in new plugs but still one cylinder was not working.  Removed valve cover to discover a bent push rod laying there.  Problem now is there are two rocker arms and only one push rod???  I guess it went through the oil drain hole and lodged in the crankcase some place.  I apparently was this way when I drove home and all while working on it. No noise or signs of issues with a metal rod in the crankcase.  The rod was bent because the valve guide has moved out of the cylinder a bit preventing the valve from opening fully thus the bent rod.  I reseated the valve guides and order new push rods.  Now the big question..... what to do about the missing push rod.  It looks like major work to pull the motor on this mower (must remove deck and electric blade clutch etc) then remove the crankcase and hope no pieces fall out because they are built as a unit.  My feeling is that I have been running it this way and nothing came crashing out the sides yet so maybe I will just take a chance that the push rod found a good home somewhere and hop for the best.  Picture shows the one bent push rod.  What do you think A. Rip it all apart and remove the way word push rod or
B. Put in new rods and cross your fingers for a while. 

[mike89]

was the other push rod even in there???  did ya buy it used I guess???

[deadeye]

I bought it new from Sears 11 years ago. It's a ZTR 7500 (zero turn).  I was thinking the same thing but the plug looks about the same as the other one so it must have been firing.  Really odd for sure.  Runs and sounds normal with the plug wire off (then again there are not push rods either).  I didn't try to run the blades after changing plugs. 

[Rebel SS]

Wow! Is that funky, or what?! If yer pretty sure it's hopefully laying flat in the pan, I'd leave it. Wouldn't have damaged the oil sump pump or laying crossed up on that, is it? Then maybe....

[dew2]

What a delema! Do it right or hope for the best.Is the lifter working? Think I' go the short route seein the engine is older and I'd guess lots a hours.install,turn by hand plugs removed an listen close,then if OK fire it up.Or maybe use a cheap scope to view in the CCase?

[Rebel SS]

If ya have a flex scope,  first thing I'd do is give the crank case a kaepernoscopy.

[deadeye]

I got the new push rods yesterday (I ordered two sets in case there was an issue with the other cylinder).  Checked the other cylinder and had to adjust the exhaust valve clearance.  Put in new rods and was somewhat surprised that they were that far out of adjustment, probably 1/8 inch.  Also, while adjusting I noticed the rocker arm would rotate to the point it almost didn't hit the valve stem.  Turns out the bolts that the rocker arms pivot on were backed out a bit which probably was the original problem.  After tightening these bolts, I had to again adjust the valve clearance which basically set the adjustment screws back to where they were.  Fired it up and drove around for a while.  Lots of pep and power.  Runs like a new motor.  I just hope the way word push rod stays where it is for the next 10 years. 

[deadeye]

So far so good.  Mowed my lawn and my son's without a hitch.  Of course the lost push rod is always in the back of my mind when I hit a bump....

[LPS]

 

[deadeye]

Well, it lasted just about a year before I had the same issue.  The valve guide backs out from the cylinder head and eventually makes contact with the rocker arm causing the push rod to bend.  I planned to disassemble the valve springs reseat the guide and peen around the edge to help keep it in place.  I went to a local "old guy in old shop that has been there for almost 40 years" to see if he had the parts and any guidance.  He said he tried using a punch to wedge the guide in place but it was not successful as after a while it failed again the same way.  He suggested replacing the head.  While looking a various old motors to determine which head (of course they cannot be the same), we found a box with two heads he had removed from a motor that blew up.  I bought it for $25.  I also bought the 4 gaskets that are needed.  Removed the head and replaced it.  So far everything's been running fine.  I hope that's the end of this story.   

[LPS]

Hey good for you DE.  Good luck. 

[Rebel SS]

Good deal! I like the way you do things!