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I have inherited a Craftsman Lawn tractor and am trying to get it going. The engine seems to be having either timing or compression problems. A mouse had made a home behind the petrol tank and chewed through some wires. I fixed the wires and the electrics are now good. It has a new starter and spark plug just before I started working on it. A neighbor has checked the timing and believes it to be good but doesn’t have the knowledge to work out what is wrong. The engine spins freely with the spark plug out but not with it in. Videos below. Spark plug in: https://youtu.be/PiPghgo6POs https://youtu.be/Ao1thHr-tlU Spark plug out: https://youtu.be/AXOg6eJ4fJM https://youtu.be/3To7Y4Av2bo https://youtu.be/CnJLimYkA4M Thanks. Update (04/06/2018) So I had the mower running for a whole season but it got worse so I decided to strip it down and indeed the compression release spring was in pieces inside the engine case. I installed a new camshaft (changed out the oil gov and all seals rebuilt the engine and it started up first time with no compression or turnover issues at all. See Below: https://youtu.be/DKcggQdvAwc I then left it for about a month, went back and it started again first time. I let it run for a while and all was good. Then the next time I came to start it I forgot to turn the fuel cut off valve on and so it ran out of gas and stalled after a minute. I turned the valve on, and got it started but then it began to run rough and now won’t start at all. I thought it was still fuel starvation but checked the carb and was letting fuel through fine. Checked the spark plug and it works fine - did smell heavily of gas when i removed it. See vids below - any thoughts? Has the timing gone? https://youtu.be/q_WvfPjqkm4 https://youtu.be/gSHX2qpLcBk I stripped down the carb, all looks good. Spark plug working good and valve spacing is all good. Here is another video of it trying to start and the good spark plug. https://youtu.be/8hKMRK0e0QU
Ryan, I think I know what your problem is. On the larger riding mower engines, there is a compression release built into the engine. Basically it is there to hold the exhaust valve open when the engine is not running. Sometimes this device fails and the valve is left closed. The starter is not strong enough to overcome the compression caused by the closed valve. You may hear a partial turn of the engine and then it won’t turn over. So…what to do? Remove the air cleaner so you have full access to the air intake to the carburetor. Put on a leather glove and put it tight over the air intake on the carburetor and keep it there while someone else cranks the engine using the starter normally. The engine should turn over easily and will probably start. BE CAREFUL IN CASE IT BACKFIRES THROUGH THE CARBURETOR. It could burn you. What you are doing is, you are not allowing any air into the cylinder so there is none to compress! Therefore it will turn over right through the compression cycle without releasing the valve. Once you get it to turn over properly, let it take in some air and fuel. You should be able to get it to run.
Ryan, if indeed a new starter and battery fully charged and engine turns over slow with plug in and turns good with plug out, a big reason for this is a valve adjustment is required. Use the 1st and 2nd link below to see the fix, the 3rd link you can determine the spec. to know what to set the valves at.Good luck. I hope this helped you out, if so let me know by pressing the helpful button. https://www.youtube.com/watch?v=0cWoEk5G… https://www.youtube.com/watch?v=NjzX-PUj… http://www4.briggsandstratton.com/miscpd…
