# bent crankshaft on push mower



## loweac (Jun 15, 2010)

I was hoping to some advice here.

We have a, I think Torro, push mower that now has a bent crankshaft. WE took it in to repair because it would not start. The place fix it, put a pull string, carborator cleaning, etc. and charged us over $100. 

We try to start it, and it would not start. Took it back and now they say the crankshaft is bent and can not be repaired. At this time they do not believe us that we never got it started, so could not have run over anything to break it.

The only thing I think could have done it was the blade was loose when we tried to start it. I think it caught a few times but vibrated and stopped. Husband tighten blade and it would not start. Is it possible to bend crankshaft with loose blade or did they not see it the first time it was repaired?


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## indypower (Apr 8, 2009)

They missed it. Probably not looking, either. The only way a crankshaft gets bent is by hitting something (rock, stump, ect.) with the engine running.


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## macart52 (Jun 5, 2010)

Indy is right on here. I used to get customers in with the same problem and I did have a straightener but I never used it, as it is a very dangerous way to fix a mower. Here's the deal...when anything is bent (especially metal) there is a breakdown in the metal causing stress. Now if that (In your case) crankshaft is bent back, then there is a weak spot in the metal. So that being said, the shaft was bent once and now we are bending the shaft again, back to straight. Now you have a very dangerous mower. With the blade spinning approx 3000 rpm, or more, suppose it breaks off? Where will it go? My guess it will probably take one or both of someone's feet off or even death!
If I were you I would junk that mower and buy another one. Now when and if you buy the next one.....Make sure it has a short shaft. You can tell this by looking at the blade under the mower. The blade will be close to the bottom of the engine = short shaft. Now by having this type of shaft, you will hardly ever bend it no matter what.

Hope this helps and good luck.

ol mac


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## 30yearTech (Sep 14, 2006)

macart52 said:


> If I were you I would junk that mower and buy another one. Now when and if you buy the next one.....Make sure it has a short shaft. You can tell this by looking at the blade under the mower. The blade will be close to the bottom of the engine = short shaft. Now by having this type of shaft, you will hardly ever bend it no matter what.
> 
> Hope this helps and good luck.
> 
> ol mac


I have seen short shaft's bent too. You won't find a self propel mower with a short crankshaft either, so unless you like to push your out of luck there.

That's not the point of his post anyway. The repair shop charged over $100.00 to repair a mower that already had a bent shaft, and still won't run. Now they are telling them it's unrepairable, and blaming them for the bent shaft.


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## geogrubb (Jul 28, 2006)

Let us start at the beginning, somewhere during this transaction we have a loose blade, when did it get loose, before or after it went to the repair shop the first time. If the engine was tilted to remove the blade to be sharpened and it was tilted with the carb down oil could have saturated the air filter and it will not start so try removing the air filter. Remove the sparkplug or at least the plug wire, tilt the mower on its side (carb side up), now turn the blade and mark several locations under the deck as you turn the blade, if both ends of the blade pass the marks at the exact same spot the crank is not bent. Post back with your findings and someone will get you going. Have a good one. Geo


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## phillipmc (Jan 27, 2008)

Also you could try removing the spark plug and temp disable the engine break (normally the handle you have to depress at the mower grip) tilt the mower the proper way and slowly turn the blade with the engine watching the center bolt for any wobble. There should be if any at all very little wobble. This will tell you if the shaft is indeed bent or not.


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## loweac (Jun 15, 2010)

The saga continues. Apparently there is evidence that the lawnmower hit something as the blade in nicked and the pull cord has signs. I plan to go to the shop tomorrow to look at this.

I just can not figure out when this happened, before we took it in the first time or between the two visits. They do not believe us that we never used it, which is sad because we have been good customers for the last 6 years. I only thing I could figure is either our lawnmower was mixed up with another, the repair guy ran over something, or some how someone got it out of our garage and used it in the two weeks we had it.

The last one might have happened as we have a renter on the property. But she has never used any of our equipments, even though offered, and we keep the garage closed when not home. I asked her but she said she never touched it.


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## light mechanic (Jul 18, 2008)

I have straighten bent shafts for years and learned from a real old fellow at the time when I was young, have never had one give a bit of problems, short or long shaft will bend and will come back to "0" in a few pulls, as a matter of fact I have two that I am doing for a local mower shop, when a customer pays $700.00 for a John Deere with all the trimmings they will pay well to get a shaft fixed, if you have a dial indicator put it on the shaft and will tell you all you need to know, always change the flywheel key also, Light Mechanic


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## Bob DiGiacomo (Jan 15, 2009)

light mechanic said:


> I have straighten bent shafts for years and learned from a real old fellow at the time when I was young, have never had one give a bit of problems, short or long shaft will bend and will come back to "0" in a few pulls,
> 
> I heard there was no way to fix a bent crankshaft, so what is the process to fixing one? Just Curious Thanks


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## 30yearTech (Sep 14, 2006)

Bob DiGiacomo said:


> I heard there was no way to fix a bent crankshaft, so what is the process to fixing one? Just Curious Thanks


You *CAN'T* fix a bent shaft, *PERIOD*!

You can straighten one, but you run the risk of the crankshaft failing while in use. You can never tell whether or not the shaft is going to fail.

Crankshafts are cast and when they get bent, they actually twist and there are microscopic fractures created. You will create more fractures, when you bend it straight. 

If you run the engine with a crankshaft that has been damaged in this way, there is the possibility that it can break off while in use. THERE IS NO WAY TO TELL if this will happen, it may never happen, but if it does, do you want to be responsible for the possible consequences of this type of repair?

Let your conscious be your guide.


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## Bob DiGiacomo (Jan 15, 2009)

Thanks that is kind of along the lines of what I thought.


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## light mechanic (Jul 18, 2008)

the motor is held on a flate plate of iron, there is two metal strips that run on each side of the crank, one hold the crank in place near the base and the other is on the outer edge of the crank, with a fine tread bolt it is pulled up then released to check if it was pulled enough, I know that you have some valid points but if you consider that all metal is cast, the crank is cast then machined it is really soft put a file on its edge on the lower end of the crank, rub it across there a few times you will see that is not like say 4140 and when they bend it is really not a lot, looking or woried about libality there are many way you can get caught in that don't have to see much television to see the lawyer commerical, if you do anything to take people's money they can get you some way, I do it to help people not hurt them, I do know the differance, Light Mechanic


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## 30yearTech (Sep 14, 2006)

light mechanic said:


> the motor is held on a flate plate of iron, there is two metal strips that run on each side of the crank, one hold the crank in place near the base and the other is on the outer edge of the crank, with a fine tread bolt it is pulled up then released to check if it was pulled enough, I know that you have some valid points but if you consider that all metal is cast, the crank is cast then machined it is really soft put a file on its edge on the lower end of the crank, rub it across there a few times you will see that is not like say 4140 and when they bend it is really not a lot, looking or woried about libality there are many way you can get caught in that don't have to see much television to see the lawyer commerical, if you do anything to take people's money they can get you some way, I do it to help people not hurt them, I do know the differance, Light Mechanic


I am sure that you are not straightening any shafts with the intention of hurting anyone. I also think that it's rare to have one break. 

I had one break on me, and fortunately there was enough shaft attached to the blade that it did not come out from under the deck. It did make quite a gash on one of the tires, (and scared the s*** out of me) but otherwise caused no real damage. 

The real issue is you simply cannot tell if a shaft that has been straightened will break or not. It's a chance I am not willing to take. When a crankshaft gets bent, it's torqued and gets twisted, it's not simply bent to the side. When you straighten a shaft however, it is simply bent to the side to get it straight again. The metal fractures and fatigues. This can lead to possible failure. 

If you think saving a few bucks straightening a crankshaft rather then replacing it is worth the risk, then it's your call. Odds are it won't break....but what if it does???????


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## light mechanic (Jul 18, 2008)

30yearTech, you right it could break but like happen to you they should not come out from under there, bet you did almost do it in you draws, probably did not forget that sound soon and you know that of the people that own on and cutting in the junk rather than they yard usually can't afford more that the cheap mower they bought and usually can't replace them, they are so appreciative for help, we can be had by anyone these days, I just do what is right and the rest will take care of it self, I had a Lawnmower shop years ago, sold the small plastic bushing on the steering arms on the old snapper rear engine rider to a fellow, the one with the looped handle, iron seat, his grandaughter was cutting in a ditch and it fell over on here, here come the lawers, the sale was .50 cents, now I am going to court, turned out that he did not put the washer or the cotter pin, so I do know about that side also as I am sure that you do, I also size up the customer before I do anything, we really work on these machines to help people not only for the money, mechanics are good people, you take care and have a great weekend, Light Mechanic


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## light mechanic (Jul 18, 2008)

30yearTech, your going to like this, I straighten two bend shafts today, one a snapper self propelled and a John Deere, both the same frame style, John Deere had the castor wheels in the front, the deere deck is much heavier than the snapper, sure not as good as the snapper used to be, quality has went down as the price goes up, Light Mechanic


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## 30yearTech (Sep 14, 2006)

light mechanic said:


> 30yearTech, your going to like this, I straighten two bend shafts today, one a snapper self propelled and a John Deere, both the same frame style, John Deere had the castor wheels in the front, the deere deck is much heavier than the snapper, sure not as good as the snapper used to be, quality has went down as the price goes up, Light Mechanic


You know my thoughts about bent crankshafts!

And we all know yours... Best of Luck with that!


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## macart52 (Jun 5, 2010)

Well the only thing I can say here is, when I was a kid we had an old....(New at the time) Rotary (The brand) mower. I was mowing the lawn when it quit. I got it fired back up and it was running rough. So I reached down and reved it up way past the governor. Thank God my foot was on top of the deck. The blade broke off, right through the steel deck, just below my foot, like it was butter and stuck approx. 20' away into the side of the henhouse, just missing my mom's head, as she was using a sickle cutting the weeds. So that learned me at a young age what a mower can do. That being said, in my shop, there was never a crank straightened. I had a couple of customers that wanted a bent crank fixed, so I fixed them by installing a new crank. I'm 100% with 30 yr tech. As he said WHAT IF?????
Another story. Man was mowing his lawn in the city one afternoon. All of a sudden the mower quit. As he was trying to start it back up, he heard his neighbors wife screaming. He rushed over to see what was the matter and her husband layed dead in they're yard and bleeding like a stuck pig from his head. Well it turned out that's why the mower quit. The blade come off and killed him. Now raises the question and I always wondered this, when I had my shop. Was the crank straightened? We'll never know!

Mac


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## LowRider (Dec 23, 2008)

did they not start the mower when you got it to show you that it was working? this is like getting a car fixed and not being able to drive it home. next time get them to start it up before you take it home, it keeps everyone honest.


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