I picked up a JD STX38 black deck with a Kohler Command 13, CV13S, it's a single cylinder OHV. The mower only needed a few cosmetic things so I finished it off and had it looking great and went to take a victory lap around the yard when all hell broke loose. It sounded like it had slung a rod but it was still running and still seemed to have ample compression. I shut it down quickly. Expecting the worst, I decided to open it up before I scrapped it just in case it wasn't as bad as it sounded, which was real bad. I took off the valve cover and everything seemed in order, no obvious damage. I removed the head cover and after some inspection I noticed something odd, a shallow indention in the piston head, it did not go through, just an indention. I looked at the head cover and saw a small piece of metal imbedded into the head cover. I removed it and saw that it had stamped a flathead screw intention into the head cover. I could make out a few threads in the now almost flat piece of metal that allowed me to identify it as a very small screw, or at least what once was.
To open the crankcase I would have had to remove the engine from the mower so I decided to wait in case that was not necessary. I put it all back together to see what it would do. I went ahead and cleaned the carb while it was off. The carb was working good before but I figured a cleaning wouldn't hurt. As I was cleaning it I discovered that one of the two choke plate screws were missing. Obviously I knew right where that other one was.
I put everything back together and double checked it all. I have good spark, good fuel delivery, the carb float is working properly, I dropped the bowl and checked that the float was shutting off the fuel and allowing it to run when the float is dropped. With the head cover back on I checked to see that the valves were opening and closing properly. I had checked the valves for damage since the screw obviously passed through the intake valve but saw no obvious damage. The valves are non adjustable hydraulic. I did not mix up the intake and exhaust rods.
When I try to start the engine now it spits fuel out of the air cleaner and when I close the choke it backfires. It will not turn over. Any suggestions?
That is not as uncommon as you think, I've seen it at least a dozen times in the last 40 years. As to your problem, two things I would check. One, check the intake valve again and make sure that it is sealing properly. Two, check the flywheel key and make sure it is not partially sheared.
Good call, now that you mention it I've had flywheel out of time and that is how this engine is sounding. I have already pulled the head cover off again to recheck the valves and I'm pretty sure they are good. I checked the rods, they look straight and undamaged. I'll pull the flywheel and check that out tomorrow.
#4
ILENGINE
Being a command engine with the hydraulic lifters. It could of over extended one of the lifters after you removed the head, and now it just needs to compress so the valves will close properly.
This is my first experience with hydraulic lifters, if that is the problem, how will I know? What do I need to do, if anything, to compress them. When the head cover is off the valves are completely closed. I can spray cleaner on the back side of them and it will not leak out, so they are closed pretty tight. I don't know if that means anything toward what you are saying or not.
