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My son hit something with our 4 year old Troy Bilt w/ 550ex B&S OHV engine and bent the crankshaft.
I tilted it on it's side, took off blade and sledgehammered the shaft straight again. (Same thing happened last year, and this worked then.)
Now it won't start. The past couple weekends I've taken off and cleaned carb, put a new spark plug in it, new gas, etc. no luck.
I crank and I get some white smoke from carb when I have the filter off. No smoke from exhaust.
It's getting a spark and seems to almost want to try to start but doesn't really even fire.
I think with the white smoke, something is trying to combust.
Did I mess up the timing, maybe? Damage the carb diaphragm? Any ideas?
I'm tired of smelling like gas every weekend....

It may be worth mentioning, once I was done beating on it and put the sharpened blade back on, it did not want to turn with the rope. I had to forcibly turn the blade to hideous grinding noises and resistance. It finally broke free and turned normally. After looking at articles and videos on timing these engines, I wonder if I made the timing gears slip a notch. Is this possible? If I need to take the whole engine apart, I may as well get a new [straight] crankshaft, eh?

did you replace the flywheel key

Crank shafts get removed then very carefully straitened either using a bending jig or a press.
Smacking it with a big hammer while still in the engine is a recipie for wrecking the engine which sounds like exactly what you have done.
Once bent & straitened, if not dead strait it will bend all by itself due to centrifugal forces and if dead strait will be substantially weakened so will bend at the slightest provication.
As your son has just proved by bending the shaft yet again.
I have seen decks with very large holes as shattered blades "exit stage right" considering just how much damage a mower blade can do you can only be considerd as an absolute fool with no regards to the safety of your son or others in the vacinity of the mower.

You have been smashing a lump of forged steel that is supported by two very soft bushes cut out of soft aluminium which must be alignment +/- 0.005" to enable the mower to run.
SO now you have gone well beyond a replacement crankshaft, it is new mower time

bertsmobile1 said:

you can only be considerd as an absolute fool with no regards to the safety of your son or others in the vacinity of the mower.

Click to expand...

bertsmobile1,
A simple answer would have sufficed. The insult (full of misspellings, by the way) was not necessary, not to mention rude. Both the misspellings and the insult diminish the value of your reply. Some manners would be appreciated here.

You didn't really answer my question anyway. Is it possible I slipped a timing notch in the gears?
So, in your opinion, the mower is trashed? Well, then engine, anyway...
And, yeah, a new crankshaft is $90 so a new mower (or just engine) would be more practical.

Thanks for the safety tip, and you might consider turning on spell check or use Chrome, as it has built in spell check. See if you can work on rewording your insults into constructive criticism. That would go a lot farther in promoting proper maintenance and safety.

ILENGINE,
No I have not replaced the flywheel key. I did not remove it. Perhaps it sheared? I had a Craftsman mower that would shear those things and would almost rip my arm off when I tried to start it. I'll take a look. Thanks!

Status update.
Flywheel key was sheared about halfway through. I got all excited that was it. But it's not. I replaced the key and pulled expecting it to rev to life, but alas it didn't. Still same symptoms. White smoke from carb, no exhaust. But it did fire for a little while, just barely running with practically no power. Did not start again though. I'm now going to tear it apart further and check the timing on the gears themselves.

Before tearing into it I would check the oil level and spark plug. While you were attempting the repair, you may have filled crankcase with fuel and or plug the air filter. White smoke many times means an oil/fuel mixture entering the cylinder through the breather.

Thanks, Rivets.
All was clear. I cleaned carb and put a new plug in it, even. I just finished pulling it apart and realigning the marks. I'm not sure if they were off or not, so I went ahead and lined them up anyway. Still no go, though I heard one good 'pop' of a fire and had some 'regular' smoke out of the exhaust, but still the same overall result, white smoke from the carb. I'm going to let it rest a bit because I do know I have oil all over the place since my operation. I'll clean the plug too.

Lyle said:

bertsmobile1,
A simple answer would have sufficed. The insult (full of misspellings, by the way) was not necessary, not to mention rude. Both the misspellings and the insult diminish the value of your reply. Some manners would be appreciated here.

You didn't really answer my question anyway. Is it possible I slipped a timing notch in the gears?
So, in your opinion, the mower is trashed? Well, then engine, anyway...
And, yeah, a new crankshaft is $90 so a new mower (or just engine) would be more practical.

Thanks for the safety tip, and you might consider turning on spell check or use Chrome, as it has built in spell check. See if you can work on rewording your insults into constructive criticism. That would go a lot farther in promoting proper maintenance and safety.

Click to expand...

When I am being paid for my professional services or publishing I do spell check.
When I am providing my services for free I don't bother.
As for you, I really do not care about your personnal safety. It appears you are hell bent on following the path you are on. Nothing I could say would cause you to reconsider your actions.
If $ 90 is more important to your than your own safety and that of your family, then that is your value judgement and you will have to live with that decision should injuries occur.
The important thing is other people who might happen across this thread after a search read it and consider the consequences of any thing they might be about do.
As a professional I am liable so bent cranks get taken out pressed clocked on V blocks then replaced if and ony if I have a written directive from the customer..

In this case I agree 100% with Bert, that is because we are both professionals and are liable for any repairs we make. I go one step farther, if I think it might be bent, it gets replaced, if the customer says NO, I stop where I am and the customer pays for my time, even if the engine is in pieces. Safety concerns are number 1 for anyone in this business. Happy homeowner can do what he likes, but if he does it for someone else, he is liable. I doubt if you have ever seen blade or crank break, but I can tell you from personal experience, I've seen it happen more than once in the shop and every time more than one of us have had to change our shorts. Remember there is a big difference between what the pro can do in repairing a piece of equipment. Homeowner doesn't carry $5,000,000 liability insurance, with the company looking over his shoulder telling him what he can and cannot do. In this country even a signed piece of paper means very little if you end up with an accident.

Thanks again Rivets. I also agree with bert. I was just miffed at the rudeness, is all. A guy visits this forum for help and gets insulted. Pretty rude in my opinion. It really rubbed me the wrong way.

I certainly don't want to chop off anyone's leg or hit a car or a dog with a rouge blade, and I certainly appreciate the advice (even if bert is still being rude by not caring about my safety). I know the brute force method is not advised nor is it recommended (other than from some people on YouTube) and I can appreciate wanting to warn others of such a repair. I also would not expect a professional to hammer a crankshaft straight. I definitely would not do that on a 160HP, 320 cubic inch Lycoming engine on a Cessna.

This 'Thor' method worked well last year on the lawnmower as a quick weekend fix reducing the vibration to nil. My wife and son were actually running it after bending the shaft! (Before the Thor fix.) I couldn't believe it when I went to mow the yard. It felt like the thing was going to shake itself to pieces. They did it again this year. My wife said the vibration doesn't bother her and she was continuing to mow the yard. Good grief! It bothers me. I can't stand an ill running machine, so I whacked it back straight again. But now it has other issues.

Kudo's to you both for your safety concerns. I sincerely mean that. However, I think most people would take offense to be calling a fool. Expressing safety concerns can be done without insults. Rivets did a fine job of that.

Case in point...
"As for you, I really do not care about your personnal safety. It appears you are hell bent on following the path you are on. Nothing I could say would cause you to reconsider your actions."

C'mon bert. You just out right insulted me with your first reply and now you've done it again! Crikey mate! What's up with that?! Are you this way with your customers? If you advise against the cromagnon approach just politely say so. Simply advise the 'fool' he should not do that, and that it would be advisable to purchase a new mower due to safety reasons, explaining what can happen. And why would I not reconsider my actions? In fact, I am. Until now, I simply didn't imagine the thing exploding and ripping the space/time continuum. That's why I came here. To learn, and I have. Thank you.

So, back to the main issue for future refernce. It doesn't run. White smoke from the carb. Carb is clean. Timing is correct. Key is replaced. Any clues? Replace carb diaphragm? Maybe I should have done that first. I'm just curious at this point. I doubt I'll actually use it anymore.

Most likely, due to safety concerns, I'll see if I can find a used mower or engine on Craigslist and be done with it.

Thanks to all.

As professionals we both get a little up tight when we see safety concerns. We never take it lightly, but at times we may come on a bit harsh. There are to many wannabes here and they need to know the results of their actions before they or someone else gets hurt. Sometimes being harsh gets the idea through the tough skulls. No harm, no foul, we'll all get over it, just trying to help.

Is it possible that you could of gotten oil in the intake when you had it on its side hammering the crank back into shape. I know Bert comes across as gruff sometimes, but he does care. The problem is we deal with customers that do really stupid things on a daily basis that increase their own risk and the risk of people around them with serious injuries.

The main reason the pro's no longer straighten crankshaft is because of the liability. There is just too much risk of hairline cracks developing in the crank that can cause failure. The hammer method doesn't allow for support of the crankshaft at the lower bearing, and can cause bending of the crank internal to the engine, which may of what happened when you experienced the locked up effect, because it was no longer straight in the bearings.

If I remember my facts correctly. In order to straighten a pushmower crankshaft 1/8 inch it has to be flexed 1/4 in in the opposite directions and takes 18 tons of force to do it. That create a lot of pressure against the bearings in the engine.

Yeah, I guess I can imagine some of the insane things you guys have seen. I do not doubt Bert's professionalism or knowledge. Everyone has their own realm of expertise and can wonder how others can be so stupid...
As a mechanically inclined guy myself, I knew the Thor method was not ideal. I kind of imagined the damage I could possibly be doing to the bearings, etc. Just hoping to get another season out of the thing. Never really thought of the crankshaft itself actually breaking during mowing and a blade and a piece of shaft escaping from under the deck. I figured a worn bearing perhaps, or a seized engine maybe. The odds of catastrophic failure may be slim, but you're right, it's not worth the risk. Thanks for the advice guys. It's just time to hang this one up. We need a 22" mower anyway. The 21" is just too small for our one acre.

Lyle .
My methods may at times be blunt, rude or strait out crass
However bitter experience has taught me that starting off with
"I don't think that is a good idea because " will generally loose the reader at the word because as they have already set a course of actions and don't want to hear anything contry.
So yes at times you need to smack someone in the face with a dead fish.
You may be cranky & upset, however I have suceeded in making you have a serious think about what you are doing and that was all that was important.
That was the sole purpose of the post.
If I really did not care I would have bothered to reply to you in the first place.
You will take whatever course of actions that you see fit & that is your decision.

But now I have your attention I will follow up with the one & only case I am aware of.
Hubby came into the workshop on Saturday afternoon looking to replace bent blade as they were having a christening on Sunday arvo & he needed to mow the lawn.
I did not have one so he asked me to straiten it.
I refused trying to explain just how dangerious it could be.
he did not listen, the blade broke striking his wife in the abdomen and lodging in her spine
She is now a parraplegic.
She had accident , sickness & wage protection insurance which covered all of the medical expenses.
However he got charged with criminal neglegance occasioning grevious bodily harm and convicted.
The insurance then persued him to recover their expenses.
I bought the mower at the insurance companies clearance sale other wise I would have never known about it.
Being a married couple 50% of everything they owned was considerd his, including the house.
Her share was just enough to discharge the mortage.
They now live in a public housing duplex she draws a dissability pension & he draws a carers pension.

All because the yard "had to look perfect" for the christining so he was obsessed about that and not thinking strait.

Thanks Bert. You're right. The slap in the face pissed me off, but got my attention. We're looking at new mowers now, even though we can't really afford it. But I'd rather eat beans and rice for a week than have a family member loose a foot. Thanks for the story. I've settled down now. No hard feelings.

Fuel, spark, compression, and timing. It will run and run right. I have equipment and motor cycles that come into my shop all the time that don't run. Never have I had one yet that I couldn't get to run right. Start small like plugs and filters and work into the bigger things. Don't jump around from one thing to the next and test parts before buying new. Yes I have done the same thing by straightening a crankshaft with a BFH (big fine hammer). Also I don't always agree what is said on a forum so don't let it unset you.