bent crankshaft

[turtlezx]

looking to by a crashed 06 came down hard on the flywheel. Is it possible to bend the crankshaft ????

Anyone experienced this

turtlezx

 

[60+ Busa Rider]

I’m not a motorcycle mechanic so I can’t answer your question directly, but most crankshafts can be straitened by a machine shop, I have straightened quite a few automotive crankshafts and camshafts. I’ve done them in a crankshaft straightener press, and I have also used a torch and then apply a big chunk of ice, the heat will push the metal and the ice will draw it back, you can watch the crankshaft move on a dial indicator. You can also use an air impact chisel (very rounded on the chisel end) to draw the bend out.

 

[WuzzaCBXRider]

I’m not a motorcycle mechanic so I can’t answer your question directly, but most crankshafts can be straitened by a machine shop, I have straightened quite a few automotive crankshafts and camshafts. I’ve done them in a crankshaft straightener press, and I have also used a torch and then apply a big chunk of ice, the heat will push the metal and the ice will draw it back, you can watch the crankshaft move on a dial indicator. You can also use an air impact chisel (very rounded on the chisel end) to draw the bend out.

Hmmph, I have never heard of this. Never heard of a bent crankshaft either, scored, gouged and broken but never bent. Thinking about it bending, wouldn’t just about everything connected to it be unusable? And about using ice, in most cases ice or water dunking hot steel will not only cool the steel and make it strong but it also makes it brittle. Am I right? For example just today I took my Honda’s bent side stand to a welder who heated it in a vise and slowly bent it back straight, nearly 3/4”. He mentioned that cooling too quickly like dunking it in a bucket of water tends to make the steel brittle and subject to failure. I’ve heard this all my life.

 

[202mphbusa]

it is possible to bend a crankshaft
in this situation I would throw a dial indicator on the flywheel and turn the motor by hand to check the runout

 

[turtlezx]

thinking the fly wheel could be bent but not the c shaft . didnt jump on it fast enough and sold for $850

on top of that the worst wiring mess ive ever seen

 

[60+ Busa Rider]

Hmmph, I have never heard of this. Never heard of a bent crankshaft either, scored, gouged and broken but never bent. Thinking about it bending, wouldn’t just about everything connected to it be unusable? And about using ice, in most cases ice or water dunking hot steel will not only cool the steel and make it strong but it also makes it brittle. Am I right? For example just today I took my Honda’s bent side stand to a welder who heated it in a vise and slowly bent it back straight, nearly 3/4”. He mentioned that cooling too quickly like dunking it in a bucket of water tends to make the steel brittle and subject to failure. I’ve heard this all my life.

As far as if the crankshaft is bent and everything connected to it be unusable, not at all, if a shaft is only bent say .010 it can be easily straightened, but if it’s bent a 1/4” then yes I would look for a different crank. The OP only ask is it possible to bend a crankshaft. For most bent cranks I straighten them in my Storm Vulcan crankshaft straightener which uses V blocks with clamps and a dial indicator and a hydraulic press. But If you already have the shaft mounted in a lathe and don’t want to take the time to move it to the crankshaft straightener then it’s not a good idea to use a press in the lathe as is can knock the headstock to bed out of alignment, so you can use a torch and make a few passes at the bend while watching the dial indicator, and the handful of ice in a shop rag just helps to speed up the process to see where the shaft is going to rest. It depends where the bend is to know how it’s best to straighten it. I probably shouldn’t have got so in depth in crankshaft straightening in my previous post.

 

[sixpack577]

As far as if the crankshaft is bent and everything connected to it be unusable, not at all, if a shaft is only bent say .010 it can be easily straightened, but if it’s bent a 1/4” then yes I would look for a different crank. The OP only ask is it possible to bend a crankshaft. For most bent cranks I straighten them in my Storm Vulcan crankshaft straightener which uses V blocks with clamps and a dial indicator and a hydraulic press. But If you already have the shaft mounted in a lathe and don’t want to take the time to move it to the crankshaft straightener then it’s not a good idea to use a press in the lathe as is can knock the headstock to bed out of alignment, so you can use a torch and make a few passes at the bend while watching the dial indicator, and the handful of ice in a shop rag just helps to speed up the process to see where the shaft is going to rest. It depends where the bend is to know how it’s best to straighten it. I probably shouldn’t have got so in depth in crankshaft straightening in my previous post.

No, details are great, it's a dieing art, and machinists, tool&die makers, and guys of your skill-set are retiring at an alarming rate...with not enough competant people with a desire to learn to replace you.
I really like Mike Rowe, and his push to bring back trades and apprenticeships...which this country is sorely lacking.

 

[60+ Busa Rider]

Thanks Six for the kind words it’s much appreciate. For the last 40 years I’ve used dial indicators and depth gauges to set rear end gears but my dad taught me to set gears with the silver backing cellophane paper from a cigarette pack, he watched how the gears made an imprint in the silver paper, he used this method for all rear end gears from automotive all the up to heavy farm trucks and they never made a noise. A funny story is I build a 64 Ford 427 cross bolt main in the Mustang pictured below and the owner wanted a Pete Jackson gear drive timing gear set, this setup required machining the front of the block to mount the idler gears and the instructions actually said use a 1/2” wide by 6” long piece of gloss paper cut from a magazine to center the gears. When I read the instructions first thing I thought was, so what do I do with all these dial indicators I have. Lol.

 

[60+ Busa Rider]

Hey Six…. I recently built this 572 Chevy engine with a Pro Charger for this Fox body Mustang, the fender says Built Ford Tuff with Chevy Stuff, lol. It’s a pro street show car tagged and insured. The owner is 82 y/o.

 

[sixpack577]

Thanks Six for the kind words it’s much appreciate. For the last 40 years I’ve used dial indicators and depth gauges to set rear end gears but my dad taught me to set gears with the silver backing cellophane paper from a cigarette pack, he watched how the gears made an imprint in the silver paper, he used this method for all rear end gears from automotive all the up to heavy farm trucks and they never made a noise. A funny story is I build a 64 Ford 427 cross bolt main in the Mustang pictured below and the owner wanted a Pete Jackson gear drive timing gear set, this setup required machining the front of the block to mount the idler gears and the instructions actually said use a 1/2” wide by 6” long piece of gloss paper cut from a magazine to center the gears. When I read the instructions first thing I thought was, so what do I do with all these dial indicators I have. Lol.

View attachment 1686535

lol, gotta love the old timer's tricks!
And as you know, that side-oiler is worth a small fortune.
I've set up a few rear-ends over the years too, and with dial-indicators, but the cigarette pack sounds alot easier...I also despise a crush-sleeve in an 8.8 Ford

 

[sixpack577]

Hey Six…. I recently built this 572 Chevy engine with a Pro Charger for this Fox body Mustang, the fender says Built Ford Tuff with Chevy Stuff, lol. It’s a pro street show car tagged and insured. The owner is 82 y/o.

View attachment 1686536

Awesome...sacriledge, Chevy in a Ford...but still awesome
lol