KT745 Bent Push Rod

[Frozen001]

Hi All,

Sorry for the long post but I thought I should give a full history. I have a KT745-3001 26HP engine on a 2013 cub cadet tractor. Late last summer it got invaded by mice and the chewed up the engine wiring on the ignition coils. So, I ended up replacing both coils and the engine wiring harness, and I ended up changing the starter since it has a lot of slop in it. I replace them with aftermarket ones, and after re-assembly all seemed good. I winterized it and stored it over the winter.

Now fast forward to this year and this spring I have been trouble shooting an issue where the engine seems to be out of timing, I.E. when turning over it will suddenly seem to want to go backwards, and then seem to back fire through the carb. So I pulled to covers off and sure enough the keyway was sheared. I replaced the key and re-assembled. Engine fired right. I mowed my lawn and it seemed to run a little rough by the time I finished. I shut it off and cleaned it up prior to putting it away, and when I went to start it the same issue I had before seemed to be back. I disassembled, but the key look fine and everything seemed OK. looking things over I discovered the starter shaft was bent, so I figured that was at least part of the issue, so I again purchased a new starter. I had noticed the valve covers were leaking a little so I decided to pull them off and while I was at it I checked the valve clearances. All of them were a bit off (too much clearance) so I adjusted them, and changed the oil and new filter. Reassembled and started it I should great and started with no issues. Started to mow my lawn and about 200ft into it I heard some lout knocking and it began to run rough. Pulled it into the garage and shut it off. Let to cool and tried to start again, and it knocked and banged, but it also had that same out of timing symptom. So disassembled again. Key looked good, pulled valve cover off and the left cylinder (look form the front/carb side) ended up having a bent upper push rod, and the lower push rod had popped off the rocker. I believe this may have happened because of my adjustment and not tightening the locking screw properly (first time I have adjusted rods), but not 100% sure on that.

So now to my questions:

1) can I just replace them bent push rod or am I looking at a more extensive repair. The motor spins free right now (plugs removed)
2) Any thoughts on the cause of this (other than my not tightening the set screw correctly.
3) Any thoughts on the out of time/backfire symptoms?

Thanks a bunch ahead of time!

 

[ILENGINE]

I think I would replace the push rods, readjust the valves correctly, but while the plugs are still out and before reinstalling the valves covers just roll the engine over by hand a few complete revolutions to make sure nothing is binding. If the valves are binding you will see the push rods flex or even bend.

 

[Frozen001]

Thanks, new push rods are on order, should be here this week. I can push the valves in by hand so hopefully nothing else is damaged.

 

[hlw49]

How did you adjust the valves. Piston on each cylinder a top dead center on the compression stroke. I turn them about a 1/4 inch past TDC and adjust them at .004 to .006.

 

[Frozen001]

What you described is how I adjusted them. Seems to fall in line what the service manual as well. I used 0.005 for the adjustment, I tightened them until I just felt friction with the feeler guage.

 

[hlw49]

Got to have done something wrong for a push rod to fall out and to bend one. Adjusted the valves on the wrong stroke?

 

[Frozen001]

Got to have done something wrong for a push rod to fall out and to bend one. Adjusted the valves on the wrong stroke?

I believe the issue stemmed from not tightening the set screw correctly. When I adjusted them both tappets were very free… about the only thing I could have done wrong is maybe on TDC of the exhaust stroke rather than the compression, but the keyway lined up like the service manual called out (keyway pointing to the cylinder you are adjusting)

 

[hlw49]

This is what the service manual for this engine says. Never did it this way just found TDC on each cylinder and adjusted it this way.

. Rotate crankshaft to establish TDC on compression stroke for cylinder 1. Check for: a. Compression will be felt through spark plug hole. b. Keyway of crankshaft will be aligned with cylinder 1. c. No rocker arm/push rod movement if crankshaft is rotated slightly back and forth. If they are moving, rotate crankshaft 1 full revolution. 2. Insert a 0.127 mm (0.005 in.) feeler gauge between end of 1 valve and rocker arm. Turn adjuster until a slight drag is felt. Hold in this position and tighten setscrew securely. Torque setscrew to 7.9 N·m (70 in. lb.). After tightening recheck adjustment. Proper valve clearance is 0.101/0.152 mm (0.004/0.006 in.). 3. Repeat procedure for other valve on side 1. 4. Viewed from PTO end, rotate crankshaft 270° (3/4 turn) counterclockwise and align crankshaft keyway with cylinder 2, which now puts cylinder at TDC on compression stroke. 5. Repeat steps 3-4 for setting valve clearance on side 2. 6. Rotate crankshaft to check for free operation of valve train. Check for clearance between valve spring coils at full lift, or bending of push rod(s) can occur. Minimum allowable clearance is 0.25 mm (0.010 in.). Check Assembly Rotate crankshaft a minimum of 2 revolutions to check longblock assembly and overall proper operation.