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Straightening crank shaft on push mower
#1
Ean
Ean
Have any of you ever straightitend crank shaft before because I was at the junk yard yesterday and saw a nice Honda mower with a bent crank shaft if you can do this I will get it
#2
Mike88se
If it's good otherwise and dirt cheap then a new shaft and bearings would be a good project. I wouldn't do it... but I could get one in good shape for less than the parts would cost to fix that one.
Good running Hondas are plentiful around here.
Mike88se
I'm going to say pass on it if you plan to try to straighten the shaft. I've heard it can be done but I wouldn't bet on it. That's like trying to straighten the crank shaft on your car. Not a good idea at all.Have any of you ever straightitend crank shaft before because I was at the junk yard yesterday and saw a nice Honda mower with a bent crank shaft if you can do this I will get it
If it's good otherwise and dirt cheap then a new shaft and bearings would be a good project. I wouldn't do it... but I could get one in good shape for less than the parts would cost to fix that one.
Good running Hondas are plentiful around here.
#3
jekjr
I know this sounds ludicrous and if I had not seen it happen I would not believe it either. However.
One time my grandfather bought a push mower with a 3.5 Briggs on it. He did not run a tank of gas through it before he hit a steel rod in the ground and bent the crankshaft on it. He then put it in the shed and bought a new one. This one was bent so bad it was locked up.
A couple of years later I needed a push mower to cut my small yard in a trailer park lot. I got it out and decided that I would try to find another mower and get a crankshaft out of it and put in that motor. I had to get the adapter off of the bottom of the motor to get it off of the deck. I did not have a puller. I loaded it on the truck and carried it to a small machine shop up the road from my house to see if I could get the old guy there to pull it off for me. When I got there and told him what I needed he looked at the mower and said, "That mower looks like new, why don't you just straighten it out"?
I told him that I did not know it could be done. He said he had done it before. We took it off of the truck, turned it up on it's side. He gave me an ax and told me to hold it up against the bottom of the shaft away from the direction the shaft was bent. He then took a 4# hammer and hit it on the opposite side. He did that several licks. All of a sudden when he hit it the shaft started to turn.
Then he would turn it to where the bend was up. The I would put the ax under it and he would hit it. He did this several times till it only had a wobble on it.
He then took a piece of soap stone and held it close to the shaft and instructed me to turn the shaft. I did it slowly and he moved the soapstone closer till it marked the shaft on the high spot. Then he would take the shaft and turn the spot with the soapstone mark on it to the top and had me hold the ax under it and he would tap it. Then he wiped the soapstone off and we turned it through checking again and then hit it again on the high spot with me backing it up with the ax.
After a few times of this he had it tried enough that you could not see a wiggle on it and there was little if any run out in the shaft. We then put the blade on it, put gas on it and started it up.
I ran it for several years.
He said that the purpose of backing it up with the ax was to keep from busting the bottom of the motor.
He also said it was bent it the throw of the shaft.
jekjr
Have any of you ever straightitend crank shaft before because I was at the junk yard yesterday and saw a nice Honda mower with a bent crank shaft if you can do this I will get it
I know this sounds ludicrous and if I had not seen it happen I would not believe it either. However.
One time my grandfather bought a push mower with a 3.5 Briggs on it. He did not run a tank of gas through it before he hit a steel rod in the ground and bent the crankshaft on it. He then put it in the shed and bought a new one. This one was bent so bad it was locked up.
A couple of years later I needed a push mower to cut my small yard in a trailer park lot. I got it out and decided that I would try to find another mower and get a crankshaft out of it and put in that motor. I had to get the adapter off of the bottom of the motor to get it off of the deck. I did not have a puller. I loaded it on the truck and carried it to a small machine shop up the road from my house to see if I could get the old guy there to pull it off for me. When I got there and told him what I needed he looked at the mower and said, "That mower looks like new, why don't you just straighten it out"?
I told him that I did not know it could be done. He said he had done it before. We took it off of the truck, turned it up on it's side. He gave me an ax and told me to hold it up against the bottom of the shaft away from the direction the shaft was bent. He then took a 4# hammer and hit it on the opposite side. He did that several licks. All of a sudden when he hit it the shaft started to turn.
Then he would turn it to where the bend was up. The I would put the ax under it and he would hit it. He did this several times till it only had a wobble on it.
He then took a piece of soap stone and held it close to the shaft and instructed me to turn the shaft. I did it slowly and he moved the soapstone closer till it marked the shaft on the high spot. Then he would take the shaft and turn the spot with the soapstone mark on it to the top and had me hold the ax under it and he would tap it. Then he wiped the soapstone off and we turned it through checking again and then hit it again on the high spot with me backing it up with the ax.
After a few times of this he had it tried enough that you could not see a wiggle on it and there was little if any run out in the shaft. We then put the blade on it, put gas on it and started it up.
I ran it for several years.
He said that the purpose of backing it up with the ax was to keep from busting the bottom of the motor.
He also said it was bent it the throw of the shaft.
#4
M
motoman
M
motoman
Straightening a shaft is part art form, and best left to a machinist who will have to charge for his time. Make the cost tradeoff . If you are curious about the technique go to youtube after search word "straighten shaft." You will see a setup of V blocks , indicator resting on the shaft, and some means of hydraulic force . The operator slowly pushes the high side past zero runout, waits for the shaft to spring back and repeats. Although blows from a hammer will move the shaft around I would not recommend it unless the mower is free and you are curious.:thumbsup:
edit: change axe to hammer
edit: change axe to hammer
#5
T
tybilly
T
tybilly
once steel is bent it changes properties (becomes weaker),after its straightened it needs magnafluxed in turn if any cracks show up,you just waisted money and time.
#6
reynoldston
reynoldston
Straighten it with a big hammer. Take that advice or leave it could care less.
#7
M
motoman
M
motoman
Again, what is a "nice Honda mower" worth? A good (can you find one?) machinist would probably charge $50-$100 for the straightening. Mag inspection another $25. If is fails it's trash time. Expensive auto heads can be straightened (part art, specialty shops). Afterwards they are heat treated. Such heads are $5K new. Apples and oranges.
#8
Fish
Fish
Here is a couple of pics of my old one. It didn't really straighten, but merely re-bends the crank so that it cuts even and doesn't vibrate, works great!!! Sorry, I don't have an engine handy to mount on there, but it is pretty straightforward.
Attachments
#10
reynoldston
Sure the kid is going to spend over a 100 + dollars to straighten a crankshaft after he takes the engine completely apart and puts it back together. Big hammer. I have done it and you will be surprised how close you can get it. Time he spends that kind of money and time he can buy a good used mower. Then on top of that I don't know what junk yard or salvage yard will sell a complete mower. They sell parts. But also I don't know his salvage yard so maybe??
reynoldston
Again, what is a "nice Honda mower" worth? A good (can you find one?) machinist would probably charge $50-$100 for the straightening. Mag inspection another $25. If is fails it's trash time. Expensive auto heads can be straightened (part art, specialty shops). Afterwards they are heat treated. Such heads are $5K new. Apples and oranges.
Sure the kid is going to spend over a 100 + dollars to straighten a crankshaft after he takes the engine completely apart and puts it back together. Big hammer. I have done it and you will be surprised how close you can get it. Time he spends that kind of money and time he can buy a good used mower. Then on top of that I don't know what junk yard or salvage yard will sell a complete mower. They sell parts. But also I don't know his salvage yard so maybe??
#11
Fish
Fish
No, you just bolt the whole engine on the straightener, take the plug out, and wire the blade brake so you can rotate the crank, takes about 5 minutes to straighten it.
Check around some of your older mower shops, They likely have one up in the attic under a pile of dust, they might sell it to you real cheap.
Check around some of your older mower shops, They likely have one up in the attic under a pile of dust, they might sell it to you real cheap.
#12
M
motoman
M
motoman
Fish, put this on youtube. I would like to see it. By the way do you and reynoldson just straighten til smooth feeling , or actually take a dial indicator reading? If not true seems like journals and bearings are short lived? This is backyard mechanics at its finest (sincere comment).:thumbsup:
But what is an otherwise "good" Honda lawnmower worth?
But what is an otherwise "good" Honda lawnmower worth?
#13
Fish
Fish
Yeah, we'll keep this one open...I gave up trying to fix pushmowers a long time ago..... Absolutely no money in it!!!!!!
But I will keep my eye open for a project for the "straightener"....
But I will keep my eye open for a project for the "straightener"....
#14
T
tybilly
T
tybilly
i forgot to mention at 2800 to 3200 rpm it decides to break it could be dangerous,so yall do what you want,once steel is bent it changes properties (becomes weaker),after its straightened it needs magnafluxed in turn if any cracks show up,you just waisted money and time.
#15
Fish
well it could be dangerous at any rpm, eh?
Fish
i forgot to mention at 2800 to 3200 rpm it decides to break it could be dangerous,so yall do what you want,
well it could be dangerous at any rpm, eh?
#16
reynoldston
Lets be practical here. If it was a customer coming to me for this job it would be new crank or nothing. We have a 12 year old boy wanting to get a mower from a junk yard. Any salvage yard I ever has dealings with know the value of what they have. They sell parts not used mowers. If this junk yard even would sell this mower they are going to get its moneys worth. Now on top of this cost to fix it right the crank needs to come out. Now we have the cost of new gaskets, seals and what other unknown parts. Then the cost of the crank shaft as to what ever that needs. I don't know this boy or his parents. Will he will have any help with this. I would say its over his head for proper repairs. Yes what is a Honda or any mower worth and what can you buy a good working mower for. I know when I was 12 years old my father would of put a big NO on this. This mower is in the salvage yard for a reason its a parts mower only. Ok if this is a learning thing take a good mower apart and put it back together.
reynoldston
Fish, put this on youtube. I would like to see it. By the way do you and reynoldson just straighten til smooth feeling , or actually take a dial indicator reading? If not true seems like journals and bearings are short lived? This is backyard mechanics at its finest (sincere comment).:thumbsup:
But what is an otherwise "good" Honda lawnmower worth?
Lets be practical here. If it was a customer coming to me for this job it would be new crank or nothing. We have a 12 year old boy wanting to get a mower from a junk yard. Any salvage yard I ever has dealings with know the value of what they have. They sell parts not used mowers. If this junk yard even would sell this mower they are going to get its moneys worth. Now on top of this cost to fix it right the crank needs to come out. Now we have the cost of new gaskets, seals and what other unknown parts. Then the cost of the crank shaft as to what ever that needs. I don't know this boy or his parents. Will he will have any help with this. I would say its over his head for proper repairs. Yes what is a Honda or any mower worth and what can you buy a good working mower for. I know when I was 12 years old my father would of put a big NO on this. This mower is in the salvage yard for a reason its a parts mower only. Ok if this is a learning thing take a good mower apart and put it back together.
#17
Fish
Look at the second pic closer, you can see the "dial indicator" on the straightener, it rides on the protective sleeve
over the crank tip.
Now if the bent is up in the bearing area, this won't work, otherwise it works great.
Fish
Fish, put this on youtube. I would like to see it. By the way do you and reynoldson just straighten til smooth feeling , or actually take a dial indicator reading? If not true seems like journals and bearings are short lived? This is backyard mechanics at its finest (sincere comment).:thumbsup:
But what is an otherwise "good" Honda lawnmower worth?
Look at the second pic closer, you can see the "dial indicator" on the straightener, it rides on the protective sleeve
over the crank tip.
Now if the bent is up in the bearing area, this won't work, otherwise it works great.
#18
Fish
briggs crankshaft straightener - Bing Videos
This is somewhat similar, but this guy doesn't support the bottom of the crank with an equalizer bolt like mine
and would probably
do damage in the crank/bearing area and be likely to leak if not crack.
Fish
Look at the second pic closer, you can see the "dial indicator" on the straightener, it rides on the protective sleeve
over the crank tip.
Now if the bent is up in the bearing area, this won't work, otherwise it works great.
briggs crankshaft straightener - Bing Videos
This is somewhat similar, but this guy doesn't support the bottom of the crank with an equalizer bolt like mine
and would probably
do damage in the crank/bearing area and be likely to leak if not crack.
#19
Mower Doctor 78006
Mower Doctor 78006
I have a good Honda 5.5Hp walk behind mower engine with a Blade brake clutch. (BBC) When I had it running I had to beg somebody to take it!! They ran garbage gas in it. It didn't run anymore after 2 months. I installed a good used thoroughly cleaned carb. It ran great. They ran garbage gas through it again!! Now I have it back and am tired of looking at it. Some people like Honda mowers, some people don't. Iam not trying to start an engine feud here. Just stating my opinion.
For the orig. poster. I would find a non running complete Honda with no crank/block damage. You would be time and money ahead going that route.
If all you want/need is a good mower there's a ton out there that don't need crank work, resealed before you hear that the engine has a knock cause it ran low on oil.
For the orig. poster. I would find a non running complete Honda with no crank/block damage. You would be time and money ahead going that route.
If all you want/need is a good mower there's a ton out there that don't need crank work, resealed before you hear that the engine has a knock cause it ran low on oil.
#20
Ean
It's not worth it anyway and I have changed a crankshaft on a push mower before I got a used one on eBay cheap and changed it with no help still use the mower to this day
Ean
Lets be practical here. If it was a customer coming to me for this job it would be new crank or nothing. We have a 12 year old boy wanting to get a mower from a junk yard. Any salvage yard I ever has dealings with know the value of what they have. They sell parts not used mowers. If this junk yard even would sell this mower they are going to get its moneys worth. Now on top of this cost to fix it right the crank needs to come out. Now we have the cost of new gaskets, seals and what other unknown parts. Then the cost of the crank shaft as to what ever that needs. I don't know this boy or his parents. Will he will have any help with this. I would say its over his head for proper repairs. Yes what is a Honda or any mower worth and what can you buy a good working mower for. I know when I was 12 years old my father would of put a big NO on this. This mower is in the salvage yard for a reason its a parts mower only. Ok if this is a learning thing take a good mower apart and put it back together.
It's not worth it anyway and I have changed a crankshaft on a push mower before I got a used one on eBay cheap and changed it with no help still use the mower to this day
#21
M
motoman
M
motoman
This has been interesting to see how much hidden knowledge is out there. I think the magflux step should be first, by the way. (my bad) That way cracks before straightening rule out further effort. What does , for instance, a more expensive crank cost? Worthwhile to straighten as you go upscale?
#22
Fish
Fish
Well, in a lot of cases, you cannot easily dismantle the engine without damaging the sump or else cutting the crankshaft off.
Generally, a pushmower is not worth that much labor and parts. When I did the straightening, the deal was, if it works,
$50 plus any parts, if it doesn't, no charge, and no I am not going to put it back together free.
Generally, a pushmower is not worth that much labor and parts. When I did the straightening, the deal was, if it works,
$50 plus any parts, if it doesn't, no charge, and no I am not going to put it back together free.
#23
C
cashman
C
cashman
Back in the 1960's, we used to straighten crankshafts on a fixture kinda like yours Fish. And just about every shop back then had one! The one we had was a "LiL Brute" and it was called an engine test stand. It had a hardened sleeve that fit on the crankshaft and the bolt on the straightener pushed down against the sleeve. It worked pretty darn good! If the engine had either a real long crankshaft (+4.00")or a real short crank (-2.00"), you could easily crack the sump trying to straighten it. It worked great on cranks with a 2.50" to 3.00" PTO length. Briggs put out a service bulletin warning of the dangers of straightening crankshafts and we stopped doing it in the shop. Briggs pointed out in the bulletin that they had switched to using ductile iron instead of steel in the crankshafts and you could end up with a fracture in the crank if it was ever bent. I don't remember ever seeing one that had been straightened that broke, but I'm sure that it could happen under the right conditions. Thanks!!!
#24
Fish
Fish
Yeah, my straightener has an equalizer bolt that comes up under the shaft close to the sump,
and the straightener bolt presses the shaft down against it, so no stress is given to the sump/bearing. The down side is that, you cannot do it on real short cranks..
and the straightener bolt presses the shaft down against it, so no stress is given to the sump/bearing. The down side is that, you cannot do it on real short cranks..