Craftsman/B&S Mower Died, Won't Restart

farmboy1(5)July 8, 2013

I have an older Craftsman Mower with a B&S engine, model # 917-387400.

I was cutting the grass yesterday with it on a 90 degree day. the grass was pretty thick, so periodically, when the mower started to chug, I'd lift it up and the cut grass would blow out from under the body and it would speed up again.

At one point, it started to chug, and I lifted it up, and it just died quickly even though I had lifted it up. No smoke, flame, oil spitting or anything exciting. It wouldn't restart.

Checking it out, I noticed that I could spin the blade pretty easily by hand, and removing the spark plug I confirmed with my finger over the hole that there was no compression. I used a wooden dowel to confirm that the piston was going up and down.

Before I tear into it (I'm used to car and motorcycle engines), I'm wondering if there's something simple I should check, a "compression lock" or something else?

I'd rather fix this if it's cheap/easy enough as most all the mowers I see for sale are the self-propelled variety, which I don't want.

Thanks guys!

vince

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bill_kapaun

Check the compression again.
Possibly, if you had a valve that didn't have enough clearance, it could expand with the heat and not seal.

    Bookmark   July 8, 2013 at 6:50PM
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farmboy1(5)

Thanks, Bill.

The first time I checked the compression was this morning, and then I checked it again this afternoon, and still no compression. The blade turns equally easy with my finger or a spark plug in the hole, or with nothing in the hole. The piston does go up and down.

Any suggestions are appreciated.

Thanks,

vince

    Bookmark   July 8, 2013 at 10:23PM
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bluemower

from your comments, the piston is working, but there is no compression. According to the sears site, this is a 12H802.

One possibility is the intake valve is stuck open. The valve stem is exposed to the incoming fuel air mixture. When ethanol fuel is used, a film of fuel residue may build up on the valve stem and eventually the valve seizes in the valve guide.

If this is the case, the valve should be removed so that the valve guide and the valve stem can be cleaned. This job is easy if you have the proper tools and knowledge.

Some shops will attempt to clean this by spraying carburetor cleaner on the exposed valve stem. This type repair may work for a while, but most likely the problem will recur. The full time use of fuel stabilizer is a good preventative measure. Do not keep old fuel in the fuel tank.

    Bookmark   July 8, 2013 at 11:04PM
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bill_kapaun

Obviously, you have a mechanical issue.
Anything from a stuck valve to the engine being completely worn out.
I'd remove the head and look for a valve stuck open.
Look for other obvious problems such as a broken piston or one that is "sloppy" in the bore.

When's the last time the cooling fins were cleaned?

    Bookmark   July 8, 2013 at 11:20PM
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