broken crank on 046

[murphy4trees]

The crank blew up.. dealer says its not worth fixing.. wants to sell me a new one..

any thoughts? To my knowledge the piston and cylinder are fine... it had good compression ...

Where are aftermarket cranks available?


thanks

 

[woodworkingboy]

Cheap enough.... aftermarket on ebay:

http://www.ebay.com/sch/i.html?_nkw=stihl+crankshaft+046&_sacat=0&_odkw=stihl+crankshaft&_osacat=0

 

[Al Smith]

Scott at chainsawr has one for about 40 bucks .

 

[Adam_P]

Any idea why it blew up?

I toasted a 460 p&c milling with it. I pressure tested the case before I put on an aftermarket bigbore p&c. You should consider that (pressure testing) too.

Tear it down and see if there's any visible damage where the bearings seat or where the failure was before you start throwing cash at it.

 

[Burnham]

Wouldn't splitting the case to install the new crank render any info from a pre-split pressure test fairly useless?

 

[Adam_P]

Yep B, I suppose it would.

I don't have a lot of experience blowing saws up.. thankfully I guess. I would just worry that something got f'd in the bottom end if that were my saw.

I have a 200t in the garage that I got off craigslist with a blown top end. I figured I could part it out but whatever happened to that thing was bad. It looked like a grenade went off in the case.

 

[Al Smith]

It probabley ate something that didn't agree with it and grenaded the piston .Usually a 200 just cooks the top end .

Busted crank ,who knows .Woobley clutch drum could do it I suppose .I don't know if you could hang a main bearing hard enough to do it or not .Usually they just spin in the case .You know normally Stihl makes some pretty tough cranks ,unusual for one to fail .

 

[CurSedVoyce]

Buy a new one and send the blown up to me Murph... I am sure I can find something to do with it

 

[squisher]

Are you sure the crank is blown? Seems unlikely with a 46.

 

[murphy4trees]

Actually its not blown, just broke in half right behind the clutch.. I was cutting a blown over 4'+ diameter oak log and there was a lot of pressure pinching the bar at the end of the cut.. not sure if that had anything to do with it, but guess it did..

 

[squisher]

Blown/broke you tell me the difference? I've had a 46 get loose before in it's old age but never had a catastrophic failure like you're describing. But obviously you've had it happen, if it's a 046 put it on the shelf for parts and buy a new 460. That saw has paid for itself long ago.

 

[murphy4trees]

I swore off buying new stihls a little while ago when corporate pissed me off... had to replace the power pruner when the shaft got bent (my bad).. other than that its all used stihl, and one husky 3120 (used) for me lately.. think I paid 300 for the 046 a couple years back.. ordered a new crank shaft and rod for $40 + shipping from chainsawr and have an totally anal mechanic to do the work for around $100.. so hopefully that will work..

 

[murphy4trees]

ps.. I was told when the crank goes it usually means it tore up the bearing, which will more often than not damage the piston & cyl... not the case here..

 

[Al Smith]

100 isn't bad to change a crankshaft .It's a couple hour job the way I do it by freezing the bearings etc .I suppose if a guy hade a case puller you could get it done faster .

 

[Ax-Man]

This is a first that I know of maybe even one in a life time for a saw or any saw for that matter . I don't know hard the saw was being pushed but I would suspect it could be traced back to a bad casting of the crank that slipped through inspection and went on through the machining process.

I have seen many things go bad on saws that shouldn't happen but they do. Recently one of my 076's broke a connecting rod or I supect it broke because I haven't taken it apart to see for sure but the turns over but the piston doesn't move. It is hard telling how that one happened , funny thing about it was the saw wasn't even cutting wood . Saw ran fine and was a pretty reliable saw and all of a sudden just broke while it was idling. Go figure.

A $100 bucks is a good price to do all that work splitting a case and redoing the bottom end. I hope your guy does a good job for that amount of money just seems to be a little light to me but if he has the proper tools he would be much faster at tearing down a saw than I am.

 

[murphy4trees]

He works in a machine shop b day and fixes saws moonlighting... He's pretty anal about everything... machinist mentality.. If he charges me a few more bucks its OK... I think the bar was getting pinches hard by big wood when it let go... I was getting late and sparks were seen flying..

 

[Al Smith]

Stihl uses a nice radiused junction where the output shaft connects to the crank throw .One reason the chain side bearing costs so much .While not impossible to break they are a very strong design .

It would seem in my mind about the only thing that could cause one to break is possibley slop in the main bearing causing vibration .Then again that much slop should have wiped the seal and it should have started to run out lean long before it broke a crank .No matter what,it's broke .

 

[Al Smith]

Seldom also do you experiance a broken rod .Recently I landed a BG 85 blower with a blown engine from flea bay just to get the shrouding .That one has a bad rod but the piston still shows the machining marks on it and clean as a pin evey where else .What caused it to go will never be known.

FWIW they use a Stihl 084 rod on many hot saws simpley because it's the strongest rod known .Just info because damned few people ever get into super hot saws including myself .

 

[woodworkingboy]

He's pretty anal about everything...machinist mentality..

I know a few long experienced machinists, but have never considered them anal. Smart guys really, at figuring out stuff. Highly skilled.

 

[Al Smith]

Machinests are just like any other skilled trade .You have good ones and not so good .It's a learned skill which involves common sense more than anything .

 

[murphy4trees]

I got an old 084, been sitting in the basement for 10+ years.. It had a air leak, which I got fixed and then it stopped running again shortly thereafter.. figured it was the same prob, but never checked.. I haven't even pulled it over lately, but would be willing to sell it...

 

[GASoline71]

What do you want for it Murph?

Gary

 

[murphy4trees]

what's it worth??? maybe $5-600???