The Official Kilt Crankshaft Thread

[Duane(Pa)]

I don't really know. Could just have been a faulty bearing. It happens. The build date on the saw is January 2017.

 

[Fruecrue]

I sure do like pics of destruction!



I think I may still have one blued from a lower rod bearing I can get a pic of later.
It was an 021 I got from a guy, chain was rocked and the saw was packed full of hay and weeds. Dude said he was reclaiming the boundaries of his yard from overgrowth.

 

[Stump Shot]

Not kilt yet, but how far does a fella trust a crank that has been over heated and turned blue? For me it's a no go in a modded saw, maybe it could live a while in a stock firewood saw long enough to be worth using again.
044 left, 440 right

 

[huskyboy]

Are some cranks blued from the factory from being hardened or is that not true?

 

[Mastermind]

Are some cranks blued from the factory from being hardened or is that not true?

I take more new saws apart than I do used ones.......and many are blue when they are brand new.

Think about it this way. If the rod gets hot enough to turn blue, how in the hell would the thin metal of the bearing cage survive?

 

[jakethesnake]

I take more new saws apart than I do used ones.......and many are blue when they are brand new.

Think about it this way. If the rod gets hot enough to turn blue, how in the hell would the thin metal of the bearing cage survive?

That’s a damn fine point.

 

[mgr1]

Are some cranks blued from the factory from being hardened or is that not true?

Thats possible. Seen it before on conrods from scooters. Blue from hardening because these ones where still in there original package.

 

[mgr1]

On what types of cranks does everybody see the most big end bearing damage, 2 or 3 piece cranck?

 

[Mastermind]

On what types of cranks does everybody see the most big end bearing damage, 2 or 3 piece cranck?

I see it on both two, and three piece cranks. I'm of the opinion that it's caused more from a lack of lubricant than from design.

 

[mgr1]

Its sure a oil problem. Did you see much cranks that break in 2?

 

[Mastermind]

Its sure a oil problem. Did you see much cranks that break in 2?

Only in saws with either high hours, or operator abuse. I guess I've seen more Stihl 044s with broken cranks than any other saw.

 

[Wilhelm]

Dolmar MS-30U weed eater.
Lower conrod needle cage gave up, at 11k rpm steel pieces quickly found their way atop the piston and seized the engine.
I wasn't happy about seeing that the conrod (with needle bearings) part number got updated with a new one (meaning that this kind of failure must have been known).
Looking at needed parts worth about 2/3 of the same weed eater new I called it a total loss and turned to another manufacturer.
I still miss the high RPM's of the Dolmar, my now three cheapo weed eaters just don't come close with 6.5 - 8k.

 

[mkf350]

FWIW...I work for one of the Big 3 auto companies, for 14 of the 20 years in an engine plant that produced v-8's. Spent a lot of time in the crank machining dept. Now the majority of our cranks were cast iron with a small percentage being forged steel.

The cranks pictured here appear to be cast iron. The blue tint that you see is a result of the heat treating required to harden the journal and bearing surfaces to be machined. BTW the forged steel cranks had even more blue hues to them.

Now there weren't very many crank failures in these engines but when there were, it usually was a result of a casting defect (voids , porosity, ect.) or exceeding the engineered HP design of crank.

Being that most ported saws don't see 50%-200% increses on power output I would bet that the first crank posted was prolly just a bad apple.

It happens even the best QC environment.

 

[huskyboy]

I take more new saws apart than I do used ones.......and many are blue when they are brand new.

Think about it this way. If the rod gets hot enough to turn blue, how in the hell would the thin metal of the bearing cage survive?

I see, so color alone isn’t a guaranteed reason to throw a crank away? At least not on a new saw for sure?

 

[jakethesnake]

I see, so color alone isn’t a guaranteed reason to throw a crank away? At least not on a new saw for sure?

Well if new ones are blue also

 

[dolmarkid]

12mm crank 10mm top end on a 440/044 best of both worlds

 

[Canadian farm boy]

10mm 044

 

[Stump Shot]

Only in saws with either high hours, or operator abuse. I guess I've seen more Stihl 044s with broken cranks than any other saw.

The 440 crankshaft is an upgrade over the 044. With slots cut in to allow more oil in.

 

[huskihl]

MS880 that came in for porting. Lower rod and bearing seemed unaffected. Not so much in the wrist pin area. Burned, crusty carbon on the underside of the crown told me that this was run lean for awhile, both on air/mix and oil. I replaced the pin and bearing and told him to change oil and use more of it

Hard to tell, but the top of the rod is blue

 

[mgr1]

Blue rod from the heat, needle cage has a little damage and the wrist pin is also a little blue.