(I also posted this in my new member reply-to post so I apologize in advance if I violated any forum protocols.)
I have an LT1018 that has given great service for the past few years. In fact, we really rely on it for fall clean up here in New England because our property has old growth oaks and maples that throw a whole bunch of leaves when the weather turns cold.
The mower began starting hard late last year so I looked on the web and found that Briggs & Stratton 18.5 HP ELS 500 (Mine is a Model 31Q777; Type 0305; Trim E1) engines have valves that go out of adjustment. I initially thought the battery was heading south, but then found out that the hard cranking was a symptom of the valves being out of adjustment. Once I reset the valves, it turned over and started like a champ.
This summer the mower was running well with no problems at all. I finished mowing and put it away one afternoon and all seemed OK but when I tried to start it a few days later, the engine turned over fast but would not start. I checked the troubleshooting section of the owners manual and found that one likely issue was the magneto air gap being out of adjustment. I reset that, checked the plug for fouling and all seemed well but the machine would still not start. I then replaced the magneto and checked the gap again but nothing. I then checked the seat safety switch (dead man's switch) for continuity and found it to be fully functional.
My next step was to check the carb solenoid and the black wire under the magneto to see if I have spark.
Back again!
I checked the gap and then for spark. I have a good healthy flash across the gap.
I disconnected and checked the carb solenoid. It seems to be working as designed.
I then opened up the rocker cover and found the top hex nut had loosened allowing the valve to go out of adjustment. I reset the valves and checked for compression. The engine huffs and puffs as it is supposed to. I even rested a Phillips screw driver against the piston top while hand-turning the motor to make sure where top dead center was and to verify I didn't have a broken crank (far fetched since there was never any "bang" while the motor ran.)
Once the valve lash was set correctly I primed the carb with a couple of spoon-fulls of gas and turned it over. I did manage to get a couple of puffs and pops but the motor still would not start. Am I missing something here?
I'm starting to think I have a timing problem but before I go any further down this path I thought I'd see if anyone on the forum has experienced the symptoms I'm seeing. Can anybody offer a suggestion or two please? Any timing or tuning wizards out there who can help?
It's me again. I found a thread on another forum that matched the symptoms I was experiencing. That thread suggested removing the cylinder head to see whether a valve seat had come loose. I removed the head and, sure enough, one of the valve seats was displaced and hanging a valve open (see attached images.) I cleaned up the piston top to check for damage and found none. I did, however, find three head bolts (top left corner when facing the engine front) that were well below the specified torque so I'm guessing there was some kind of event that worked them loose. I'm now ordering a replacement head and gasket set to repair the motor.
