# Proper way to use a crankshaft straightener



## John Lolli (Nov 3, 2005)

I know this is a very touchy subject so please dont chastize me. Last year I bought a crankshaft straightener at an farm auction. It was in what appeared to be really good condition with all the accessories including an adaptor for two cycle engines. Someone gave me a Honda mower with a slightly bent crankshaft. I was excited because I could finally use the tool. The straightener I have is the two bolt kind. I straightened the crank by tightening the outboard bolt until the needle moved 2-3 marks past zero in the opposite direction. I then tightened the inner bolt which put pressure in the opposite direction. I did manage to get the crank straight however I am not sure I used the correct technique. Could someone please explain to me the proper way to use this tool. I do not have a mower repair business and this is just a hobby for me. Thank you.


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## light mechanic (Jul 18, 2008)

John, I have done it for years and learned from a fellow that done it ever sense mower had come out, never heard of a problem and I have done many and still do a few, I have a homemade one with that said I don't know what your looks like, but on mine when the enine is mounted, I have one plate with a solid thread bolt that holds the crank in place at the base and the other on the end of the crank, I have a trust bearing on it and I can put some serious pull on it with little effort, with the bent part of the shaft facing down I tighten and make the pull, loosen both of them and recheck it again, I have found that I mark the crank with something to see if I pulled it over the other way, I have a blade bolt that I cut the head off and leave that in the crank, helps extend the movement out to see better then I put the dial indicator on it to get it to zero, if you get a chance post a pic of your and I will do my best to get one of mine posted


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## John Lolli (Nov 3, 2005)

light mechanic -- thanks -- If you go to the following link, you will see my unit and some of the accessories. Scroll down about half the page

http://www.jackssmallengines.com/service_tools1.cfm


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## light mechanic (Jul 18, 2008)

John, I seen the one that you were talking about, guess they would work, I would think the design that I have come from many years ago, did you get enough enfo. to understand how they work, would be glad to share more, I will get some pictures with an engine on mine and see that you get it, holler if you need more until I get the pictures, have a great day, Light Mechanic


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## John Lolli (Nov 3, 2005)

Light Mechanic -- thank you -- In addition to your instructions someone sent me the actual instructions for the unit that I have. Ragarding your home made one. When I was investigating straighteners about a year ago, I came across sketches on the internet for a home made unit. The unit had one outboard bolt with the head ground in a kind of half circle so the shaft would ride on it. The gentlemen who posted the plans commetned that he had straightened many shafts with it. He used a piece of channel iron for the frame. Pretty ingenious I thought.


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## light mechanic (Jul 18, 2008)

John, that would be neat to see also, I got mine from an old mechanic, I will try to get some pics by the weekend for you, might need to clean and paint it, 30 years there is not much paint on it, I had zero dollars in it when I built it, has paid for it self severl hundred times, take carem Light Mechanic


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## sluggermike (Apr 19, 2007)

Light mechanic did you ever post a picture of your crankshaft straightener? I would like to make one. I don't have any bent cranks around right now, but you never know when you might need one.
Thanks


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## light mechanic (Jul 18, 2008)

Slugger mike, will do by best to get it done soon, I will post pic and some sizes of what it is made from, hope by Monday, take care, Light Mechanic


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## John Lolli (Nov 3, 2005)

Try this website. It is an example for a home made one. This one only uses one bolt to straighten the crank. Although the person said he has fixed many shafts, it looks like it would be very easy to crack the engine base or ruin the bottom bearing.

http://www.fieldlines.com/story/2004/9/4/55837/29592


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## light mechanic (Jul 18, 2008)

John, mine is not made that way at all, mine does offer support for the crank shaft at the base, I might not get the pic's for a couple of days, twisted my ankle while in the shop, flat floor, did not step on anything, go figure, not sure about that but am sure its swollen and red, hurts like heck, not good for a tinker, Light Mechanic


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## John Lolli (Nov 3, 2005)

Ironically, there is a crankshaft starightener like mine for sale on ebay right now. The item number is Item number: 120293874540 Check it out.


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## sluggermike (Apr 19, 2007)

I was wondering why some people seem to have an ethical problem with straightening the crank on lawn mowers. Does this weaken the crank causing it to fly off and injury someone? Has anyone ever heard of this happening?


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## light mechanic (Jul 18, 2008)

SluggerMile, guess it has been 40 years ago when I first saw one done, we went to a fellow house a little home shop when he did one for us, a few years later I went and asked the older man about the machine and how it works so well to be home made, got on to the subject about it breaking, like he said it is not make of cast Iron it is steal it would have to be bent back and forth several time to even start to weaken it, they usually bend about an inch below the base, so say if it were to part there, so say that it would break, the blade and the shaft attached would have to get out from under the mower, I don't think so, I have done over the past 30 years learning from the old fellow who let me copy his machine, 200 machines, once the word is out there are a lot of them, I have never had a failure, if we live in fear of what can and could happen, we better stay home and lock the door, I works for me, may not for others, face it, when someone is pushing a mower to cut grass, they need all the help they can get, if they were well of the would have a ZTR like us, Light Mechanic


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## sluggermike (Apr 19, 2007)

Light Mechanic, thanks for confirming my feelings on the subject. I'm sure there are others out there that will also appreciate your answer. Unfortunately I don't have a ZTR. I live in Southern California where you are lucky to have a yard, but that not to say that If I could get a hold of one cheap I would for my small postage stamp size lawn. My neighbors who all have "mow and blow" already think I'm nuts and this would confirm it in their minds.
When you get a chance, I would appreciate seeing pics of your straightener.
Thanks


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## light mechanic (Jul 18, 2008)

Sluggermike, I will post some pics and the measurements of the machine, I twised my ankel this weekend in the shop, might be few days before I can get around good enough to get some pic's, think that I am going to paint it first, if you decide to make one you can make some good side cash and help people out, it is a win win deal, take care, Light Mechanic


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