# vibration in push mower?



## kmincey (Jul 14, 2008)

Ok brand new mower bought it in may it's a troy built 21in cut with briggs engine. engine code (126t02-0675-b2)
I accendently ran over a rock with it and it has a little vibration in it now. I got a new blade HOPING it was the cause but the vibration is still there. I tried turning the blade looking for uneven turning but didnt see any thing. Is there a easyer way of telling if the crankshaft is bent?


----------



## dawgpile (Apr 28, 2008)

I'd consider replacing the blade holder also, which I'm making the assumption this has some form of.

Regarding the crank, the best way to check it is to measure the 'runout' with a dial indicator held against it while turning it. I realize you probably don't have that setup but a local shop should be able to do this test for you quite reasonably. However, unless you hit a really big rock, chances of the crank itself being bent are probably pretty small. Usually, other internal components will fail before the crank gets bent.

Keep in mind that one of the other things that intentionally happens when you hit something is the flywheel key will partially or fully shear. Since you indicated you can restart it, it is at most, only partially sheared. I would replace it without question, to be sure this is OK.

Let us know what you find out....


----------



## light mechanic (Jul 18, 2008)

I would say that if you changed the blade and it still has viberation it is the crankshaft bent, remove the spark plug wire, or even remove the plug, so you don't get an accident start, with your new blade on there turn the engine and see if the blade when turned 180 degrees is at the same spot on a fixed spot under the deck, if it does not come to the same height it is bent, I have a homemade crankshaft straightner just finished doing one today, it ran but was out 25 thousands, third pull I get it to 0, charge 30 to do that kind of job, let us know what you end up with, good luck, light mechanic


----------



## kmincey (Jul 14, 2008)

Thanks for the help dawgpile and lightmechanic,Sorry it took so long to wright back vaction and stuff. But any ways I took the fly wheel off and the key was alittle messed up. So I put in a new one and now it runs like it should. I don,t feel the vibration any more so the crank should be fine


----------



## light mechanic (Jul 18, 2008)

glad for you, that what you called hitting it just right, I went by a Lawnmower shop this Friday there was a young fellow that had a new push mower, first time he used it and hit something in the grass, the fellow at the shop told him, cost less to throw it away than to fix a $ 250.00 dollar mower, the young man did not get up set just looked disapointed, he had on a Army uniform, said to the owner of the shop if he did not mind that I would straighten the shaft for free and the shop gave him a new blade at no cost, I brought it back there for him to pick up Saturday, they said he was so happy, so glad to be able to help, light mechanic


----------



## newz7151 (Oct 15, 2006)

*********


----------



## ldj1002 (Oct 13, 2007)

newz,
I have straightened many, many crankshaft in the past 55 years and know of many others that have and never saw or heard of one braking. Those cranks are made of soft material.


----------



## wheelerman (Jul 19, 2007)

Straightening a crank is not a problem untill someone is injured.Then it's a huge problem that will cost you everything.just don't do it.


----------



## ldj1002 (Oct 13, 2007)

I think that small bolt holding the blade on that has threads cut in it is much more likely to fail causing a blade to go flying through the air than a straightened crankshaft. I think that at least those bolts should be rolled, not cut threads. But, what do I know?


----------



## 30yearTech (Sep 14, 2006)

ldj1002 said:


> But, what do I know?


?????



ldj1002 said:


> think that small bolt holding the blade on that has threads cut in it is much more likely to fail causing a blade to go flying through the air than a straightened crankshaft. I think that at least those bolts should be rolled, not cut threads.


Blade bolts are Grade 8 bolts and much harder then the shaft they are screwed into. Crankshafts are soft, and when they are bent they actually twist, developing microscopic cracks. Straightening a shaft can cause more cracks to develop and exaggerate the ones already present. 

Straightening a shaft does not mean it will eventually break, in fact it may never break. There is however the possibility that it can break and when a blade is attached traveling at 19,000 feet per minute, do you want to be around if it does break?? Kinda like playing Russian Roulette with a lawn mower blade!

Straighten them if you like, it's up to you. I will never endorse this practice nor perform this procedure. 

You would be wise to explain the possible consequences to any customers that you do this for!


----------



## newz7151 (Oct 15, 2006)

*********


----------

