QuestionQUESTION: I have 3 or 4 yr old John Deer L100 w/ a B/S OHV engine. I mowed for 2 hrs in VERY heavy grass, mower running fine but sometimes lugging down in heavy grass. Stopped for two hrs. Came back and mower won't start, backfires weakly now and then. Plug OK (2 months old)and firing, fuel fresh (drained 1/2 tank anyway in case some water got in). Valves working, though don't know if seating properly. Had recent pro repair which found bent push rod bcause a nut somewhere worked loose. Repairman said piston and cyliner not damaged. I can put my finger over the plug hole and turn engine over and my finger isn't pushed off by compression. This doesn't seem right. Ideas?
ANSWER: No it sounds out of time. Check for broken flywheel key. Or it will have to be opened up and checked. If there seems to be no or little compression the valves may not be closing all the way. A spring keeper may have come off. You say very heavy grass. Did you clean under the deck? Is the grass very heavy because it is long and being cut short. Are you mulching? If heavy you may have to discharge it away from the uncut grass. Take a look at these suggestions and see if it helps.
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QUESTION: Heavy grass in unused vacant patch next to my place that I mow periodically for owner. thick bermuda 10-12" high. I was discharging, not mulching. Can I see broken flywheel key without pulling flywheel, with just shroud and screen removed? There was no sudden impact, but could heavy load on mower deck break/deform key? Sorry, what do you mean by "opened up and checked? Removing head, etc?
Answer10" or 12" Bermuda grass is not "normal mowing". I am sure if you asked JD they would say hat they have different mowers for those conditions.
Heavy grass like you mention will cause the engine to stall. You would have to mow it down in several passes lowering the deck each time. Does the engine act the same when you mow under normal conditions? If so there is the answer.
A broken flywheel key can be seen by removing the blower housing and the flywheel nut and lifting the flywheel off. If you have to check the timing marks the engine would have to be removed and the sump taken off. Then you would inspect the flywheel gear mark and camshaft mark. They should align with each other. If they do then check for another bent push rod or broken valve, valve spring or slipped keeper.
A sheared or partially sheared flywheel key will cause an electrical miss because it changer the ignition timing. You would notice popping back through the carburetor. If electrical and not the key you would have to replace the ignition coils. Hope this helps.
