lawn mower accident & symptoms

phrog(VT)April 25, 2010

Fairly new (last year's) Honda self-propelled mower hit a paint can lid, which wrapped itself around one end of the blade and stopped the mower dead.

Had to pry the lid off the blade, and it seems to cut OK. The main problem now is the engine revvs when it's idling, not a lot but as if you were tapping the gas pedal of car slightly. The fast/slow cycle is about a second or two each. I don't think it happens when I'm actually mowing.

What would cause the sudden onset of this after what happened? Thanks.

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The rpm cycling up and down is called hunting. Our mower did this when the carb got partially clogged with varnish from the gasoline. This happened gradually, over 4 or 5 years of use. I was able to get it cleared up by adding carb clean-out solvent to the gas tank. I don't know how or why the sudden stoppage you describe could cause this problem.

    Bookmark   April 25, 2010 at 11:51PM
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It's possible that you have damaged the flywheel key and timing is off.

    Bookmark   April 26, 2010 at 8:25AM
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Orangedotfever, if that's what happened, is it a necessary repair? Expensive?

    Bookmark   April 26, 2010 at 10:00AM
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It should be checked and the key replaced while you're in there. Remove the flywheel and check the key that keeps the flywheel from spinning on the crankshaft. It's all labor as a new key should be less than $1.

    Bookmark   April 26, 2010 at 11:22AM
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I would say IF your flywheel key is, in fact, damaged, it's a needed repair because the flywheel is going to continue to be in the wrong position, thus throwing off your mower's timing, and it's likely going to fail completely at some point, thus leaving you with a dead mower.

As for the cost of a repair: almost always expensive if the shop does it for you, almost always inexpensive if you do it yourself. It all comes down to whether you actually have a flywheel key problem, and if you're willing and able to fix it yourself. On your ability to fix it yourself, it's like almost any mower repair: not complicated if you have tools and patience and attention to to detail, can read and follow directions and diagrams, aren't afraid of screwing something up, etc. The worst that can happen is usually that you end up having to take the thing to the shop, which is no worse position to be in than if you'd just done that to begin with.

If your mower is still cutting grass OK, I'd certainly try to live with it as-is until the fall, when the repair backlog will be substantially less (a lot of shops now are backed-up over a month on mower repairs).

    Bookmark   April 26, 2010 at 11:25AM
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One more question: is this a repair that I could trust to a good but non-Honda mower repair place, or should I bring it back to the dealer?

Difference is 5 minute drive vs 2 hours, and local probably would cost a lot less.

    Bookmark   April 27, 2010 at 8:04AM
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Any mechanic can do it. Taking the time to properly torque the flywheel is another topic.

Your accident certainly could have partially sheered the key, but in my experience, this doesn't cause an engine to surge at low speed. And you say at high speed it works fine (mowing). It will manifest itself as hard starting, kicking back when pulling, and a miss at high speed.

I don't suspect the key just yet, even though something DID happen.

    Bookmark   April 27, 2010 at 11:21AM
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Any decent mechanic can do the diagnosis and repair. Save your time and money and go with the local shop.

    Bookmark   April 28, 2010 at 3:33AM
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Is it possible you had some sluge in the bottom of the carburetor float bown and when you tipped and jostled the deck around you got that crud in the idle or main jet? Might just need to clean out your carburetor.

    Bookmark   April 28, 2010 at 8:44PM
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I really don't suspect the key is the problem but since you hit something with the blade it's a good thing to check and cheap to fix if you do it yourself. Surging is usually a fuel issue.

    Bookmark   April 29, 2010 at 12:45AM
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