The engine on my 17 year old Craftsman lawn tractor appears to have suffered some significant failure. It's a 15 HP single cylinder Kohler Command. It has performed reliably for all these years, the only repair was the replacement of a deteriorated breather hose 7 years ago. It has been properly maintained for its entire life.
Here's the recent evolution of the problems:
The engine fired up and ran fine the first mowing of the season (April). The following week, it started to crank but stopped turning after a very brief time (perhaps one rotation of the flywheel). I gave the battery a quick charge and it started up later that day. I then bought a new battery believing that was the problem. A week or two after installing the new battery, it exhibited the same starting problem. This time I noticed that if I held the key in "start" position, the flywheel continued to rotate very slowly and after about 5 seconds it would crank normally and fire right up. Once started, it ran normally with no other symptoms other than an unusual amount of oil smoke on startup. For the next few uses, it either started right up or would exhibit the slow, then normal cranking before firing up.
Last week I attempted to start it and this time the flywheel didn't move at all after a short (normal) rotation. I then made several attempts at starting by turning the key to "start" position then off. After about 6 or 8 tries, the engine cranked normally and then acted like it was starting but only made popping sounds (like backfires). At that point I noticed that there was fuel dripping from the muffler.
I then removed all of the covers, carburetor and valve cover. One thing I found was that (prior to removal) the carburetor throat was full of gas. I rotated the flywheel by hand and noted that the valves were opening and the springs and rest of valve gear appeared intact. It appeared that the flywheel/magneto magnets passed the coil/pickup shortly after the intake valve opened (as well as sometime after the compression stroke). I reassembled the engine and cleaned the carb and installed a new float/needle/pin.
It appeared that the carb was no longer overfilling and I attempted to start it. The engine cranked strong but nothing happened. I put a few drops of gas in the opening to the carb which then resulted in the popping and backfiring. To me it acts like it has somehow "jumped timing", but I'm not sure how that would have happened.
I'm seeking suggestions on what might have failed or what the next step in diagnosing it might be. I have only a moderate amount of mechanical experience and seeing as to how it's such an old mower/engine, I'm trying to weigh how much time/money/effort would be reasonable. (the mower deck works, but has begun to show some rust-through on the deck, so its lifetime is limited).
In addition to the timing question, this engine has a compression release mechanism and I wonder if it could have broken. It is also equipped with a fuel shutoff solenoid on the carb bowl.
Any info would be appreciated.
BTW - Engine has Rotella T-5 10W30 in it....
Here's the recent evolution of the problems:
The engine fired up and ran fine the first mowing of the season (April). The following week, it started to crank but stopped turning after a very brief time (perhaps one rotation of the flywheel). I gave the battery a quick charge and it started up later that day. I then bought a new battery believing that was the problem. A week or two after installing the new battery, it exhibited the same starting problem. This time I noticed that if I held the key in "start" position, the flywheel continued to rotate very slowly and after about 5 seconds it would crank normally and fire right up. Once started, it ran normally with no other symptoms other than an unusual amount of oil smoke on startup. For the next few uses, it either started right up or would exhibit the slow, then normal cranking before firing up.
Last week I attempted to start it and this time the flywheel didn't move at all after a short (normal) rotation. I then made several attempts at starting by turning the key to "start" position then off. After about 6 or 8 tries, the engine cranked normally and then acted like it was starting but only made popping sounds (like backfires). At that point I noticed that there was fuel dripping from the muffler.
I then removed all of the covers, carburetor and valve cover. One thing I found was that (prior to removal) the carburetor throat was full of gas. I rotated the flywheel by hand and noted that the valves were opening and the springs and rest of valve gear appeared intact. It appeared that the flywheel/magneto magnets passed the coil/pickup shortly after the intake valve opened (as well as sometime after the compression stroke). I reassembled the engine and cleaned the carb and installed a new float/needle/pin.
It appeared that the carb was no longer overfilling and I attempted to start it. The engine cranked strong but nothing happened. I put a few drops of gas in the opening to the carb which then resulted in the popping and backfiring. To me it acts like it has somehow "jumped timing", but I'm not sure how that would have happened.
I'm seeking suggestions on what might have failed or what the next step in diagnosing it might be. I have only a moderate amount of mechanical experience and seeing as to how it's such an old mower/engine, I'm trying to weigh how much time/money/effort would be reasonable. (the mower deck works, but has begun to show some rust-through on the deck, so its lifetime is limited).
In addition to the timing question, this engine has a compression release mechanism and I wonder if it could have broken. It is also equipped with a fuel shutoff solenoid on the carb bowl.
Any info would be appreciated.
BTW - Engine has Rotella T-5 10W30 in it....
