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After 23 years of trying, I finally managed to run a mower into the heavy bronze water shut off at my curb. The mower (and I) lost. The blade shattered the bronze water valve cover, the engine stopped cold, the air filter blew off and after I restarted, the engine ran erratically, very loud and bogged down with even a little bit of grass to cut.

The engine model is a B&S 09P602-0137-F1. DOM 06/01/2020 Ser # 2006011148371.

I pulled the flywheel and the key was a little deformed, so I replaced it. Not a lot, but it did have a crease in it. Replaced the blade too, while I was at it. Put it back together and it runs, but it is very loud and runs way too fast. Lots of vibration translated to the handle--not pleasant. I manually adjusted the engine speed using the linkage and even though I can slow the RPMs down to about where it should be, it's still shaky and too loud at that speed. Something's still wrong for sure.

What should I look at next?

Thanks--

Check for bent crankshaft.

Thank you! Was afraid of that.

If it is in fact a bent crankshaft, find the high point of the bend shaft with the mower on its side (oil dipstick side down) and use a good sledge hammer to straighten it out. Some people hate this but I have never had a problem. Note that you will never get it perfect with this method, but you can get it good enough so that it won't noticeably vibrate.

Definitely bent. I've managed to get it back *close* to straight again. Running much smoother now (duh).

But it's still running at high RPM. I can adjust that by bending the linkage, but that seems like a cheat. Something else must be responsible for the high idle.

What would be likely suspect(s) for that?

artemjemmy said:

If it is in fact a bent crankshaft, find the high point of the bend shaft with the mower on its side (oil dipstick side down) and use a good sledge hammer to straighten it out. Some people hate this but I have never had a problem. Note that you will never get it perfect with this method, but you can get it good enough so that it won't noticeably vibrate.

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Miraculously, I had an length of heavy pipe that fit right over it. Whaled on it a bit and it came 'round.

Probably something got jammed or disconnected when the air filter blew off. Which I've never heard of.

Richard Milhous said:

...when the air filter blew off. Which I've never heard of.

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Not a good sign

artemjemmy said:

If it is in fact a bent crankshaft, find the high point of the bend shaft with the mower on its side (oil dipstick side down) and use a good sledge hammer to straighten it out. Some people hate this but I have never had a problem. Note that you will never get it perfect with this method, but you can get it good enough so that it won't noticeably vibrate.

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And will deform the bearing material and kill the lower seal. Hope you meant remove the crank from the block first.....

slomo said:

And will deform the bearing material and kill the lower seal. Hope you meant remove the crank from the block first.....

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Have you ever actually done this? I have never had a problem bending crankshafts with a sledgehammer. OP just did it and his mower is fine! Lol!

Never used a sledge to beat on a crank that was still in the block. Never entered my common sense box of tricks.

So are you saying a sledge will not hurt the metallic bearing and seal areas around the crank? Aluminum block and a rubber seal? LOL LOL

I take off blade and slide o piece of heavy pipe about 2 feet long that just fits over crank shaft,turn mower on side ,turn crank to high bend is up then hit pipe sharply with heavy hammer until crank is straight

nicdar said:

I take off blade and slide o piece of heavy pipe about 2 feet long that just fits over crank shaft,turn mower on side ,turn crank to high bend is up then hit pipe sharply with heavy hammer until crank is straight

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I bet if you hit the crank directly you'd have problems. Or if the crank was bent really bad and required repeated pounding. I've got one that leaks a bit at the bottom seal; pretty sure the crank has been straightened because when I got it the blade was broken. Not just bent, had a chunk bit off.

Using a pipe to give you say 20x leverage reduces the lateral impact load on the crank by 95%.

EDIT: Actually it's more complicated than that. What's the distance between the top and bottom crank bearings? Between the bottom bearing and the bottom end of the crank?

Richard Milhous said:

EDIT: Actually it's more complicated than that. What's the distance between the top and bottom crank bearings? Between the bottom bearing and the bottom end of the crank?

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No need to calculate. Guy is playing with dynamite.

slomo said:

No need to calculate. Guy is playing with dynamite.

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Have a beer or few. Calculating is fun! So is dynamite.

I turn the mower on it's side and put a very thick piece of angle bar between the base of the crankshaft (i.e. at the lower seal) and my concrete driveway and wail away. This angle bar absorbs the blows so the engine housing and seal don't have to. Have had very good success this way.

slomo said:

No need to calculate. Guy is playing with dynamite.

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You must be one of those same people who think using starting fluid will shear the flywheel key, right? Or that using a hammer and prybar to break a flywheel loose will destroy a crankshaft?

artemjemmy said:

You must be one of those same people who think using starting fluid will shear the flywheel key, right? Or that using a hammer and prybar to break a flywheel loose will destroy a crankshaft?

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Don't forget I think Slick 50 is THE best oil treatment on the market. Better than what you use.

Richard Milhous said:

Have a beer or few. Calculating is fun! So is dynamite.

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Bent then straightened cranks sometimes break. It's not too big a deal if there is just a pulley on the end of that crank,but a double ended sharp blade ,turning at high rpm,just a foot or two from your ankles!??
Replacement engines can be less expensive than a trip to the emergency room.