The Official Kilt Crankshaft Thread

[RIDE-RED 350r]

That's the trick too!

Be nice if we could rebuild those little buggers. They are NOT cheap to buy new OEM

 

[teacherman]

Post your dead cranks here fellers. No.......not those cranks. The blue pills will bring those back to life. I'm talking about those crankshafts outta saws that gave up the ghost.

Here's one from a MS261C I pulled apart. Stock saw except for a muffler mod. It was not a beat to death saw......just a average working saw. Wrist pin, and main bearings are just fine after a trip thru the ultrasonic. The piston lost the fight with the debris, but the jug is ok.

So.......why did this crank die an early death?

View attachment 114910 View attachment 114911 View attachment 114912
The crank stub has no measurable wear.

View attachment 114913

I'm wondering if it was tuned to go too fast. These new saws get their performance from more spin rather than more grunt and torque, and I could see it being set to 17K to win a saw race or something, which it might well have done. I've been hearing that new Stihls have sometimes been failing with Stihl Ultra at 50:1. Might it also be lower octane fuel?

Stihl Über Alles!

 

[RI Chevy]

I thought it was a 261 mtronic???

 

[Mastermind]

I'm wondering if it was tuned to go too fast. These new saws get their performance from more spin rather than more grunt and torque, and I could see it being set to 17K to win a saw race or something, which it might well have done. I've been hearing that new Stihls have sometimes been failing with Stihl Ultra at 50:1. Might it also be lower octane fuel?

Stihl Über Alles!

It was an RPM limited M-Tronic unit......so over-speeding is unlikely. Poor quality fuel is also doubtful since his other saws are fine. I'm really leaning toward a defective bearing on this one.

 

[treesmith]

The Evans clan that I descended from comes from Wales. So......maybe.

Ah, that's where the accent comes from...

Wales, where men are men and sheep are nervous

 

[Mastermind]

Ah, that's where the accent comes from...

Wales, where men are men and sheep are nervous

Ma said that's were the quick temper comes from. LOL

 

[Lightning Performance]

Oooo stroker cranks. There you go guys. Take Husky rods and stickum on Stihl cranks. Stihl has burnt rods and dont break and Huskys have fried mains.

Speaking of cranks... I'm considering making a saw crank into an acc oil drive only. Thoughts? Models?

 

[Al Smith]

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.

That pretty much covers it .I too work in an engine plant and in the past have worked in crankshaft departments .Fact once I had a Landis grinder go bonkers and cut a Ford 460 iron crank right into and throw the parts at me .Those things weigh about 85 pounds.Two 40 pound chunks of cast iron trying to put good old Al right into the promised land in one fell swoop .

 

[Quzick]

A Customer came to visit yesterday, and asked how to assemble his chainsaw....
and he said that his brother tried to put all together, and he also said that his brother has a masters degree in our Estonian Technical University....

 

[Al Smith]

This crankshaft discussion brings up kind of a mystery to me .I assume they are assembled with an induction heater and a press . To disassemble one would require the same . Evidently when Falicon builds a stroker crank they must use an offset pin. That would be in my pea sized brain the only way they could do it .I'd love to see how it's done . It certainly is not something you could do in the average shop .

 

[mgr1]

Here is a pic from a off set pin.



On sawhawzz ore something was a thread from somebody that made this at home. He even shortend conrods en welded it back together.

 

[mgr1]

https://mfrindustries.com/poulan-3400-countervibe-race-chainsaw-project/

This is project nr 1. Nr 2 is the offset pin. When i find it i will post it.

 

[tree monkey]

https://mfrindustries.com/poulan-3400-countervibe-race-chainsaw-project/

This is project nr 1. Nr 2 is the offset pin. When i find it i will post it.

that's dieselfitter's work. there is a thread on it here somewhere. I did one as well. 385 wild thingy.

 

[LBracing]

You don't need to heat the crank to press it apart , a 20 ton press , a bushing to press against and a punch to push the pin out is all you need . Seems much more complicated than it really is . With a pressing jig to put it back together I can press it apart and pin it back in under 15min usually .

Falicon and most cranks shops don't use offset pin . Think how you would get the bearing in place on a +4mm stroker
Two main way its done :
-Bore the pin hole offset , press in bushings to get back to original diameter and weld those in place .
-Weld the hole and bore it offset afterward .

A lot of the hardness is lost doing this and thats why they weld the pin in place .

 

[Roost426]

How bad is wear on the end of the crank stub and what is the main cause of it?

 

[redlight066]

Haven't had a good kilt crankshaft in a while. Think this one qualifies ;-)
Oil line is playing peek-a-boo. Lol. I assume there was a casting flaw in the piston. Some how the AM cylinder survived. Kinda ... Owner of the tree service was present when I tore it down. Luckily he had a complete 066 case with an OEM top end that has a scored piston. Looks like the OEM cylinder will clean up from the donor

 

[Mastermind]

Haven't had a good kilt crankshaft in a while. Think this one qualifies ;-)View attachment 157761View attachment 157762
Oil line is playing peek-a-boo. Lol. I assume there was a casting flaw in the piston. Some how the AM cylinder survived. Kinda ...View attachment 157764 Owner of the tree service was present when I tore it down. Luckily he had a complete 066 case with an OEM top end that has a scored piston. Looks like the OEM cylinder will clean up from the donor

 

[redlight066]

He said it made an awful racket when it let go and a bunch of oil poured out of the saw. I pulled the muffler and a chunk of the wrist pin casting fell out. "Cuz, that don't look good".

 

[redlight066]

Something to be said for the right song for the moment....

 

[Mastermind]

Something to be said for the right song for the moment....

That's what happens when you work alone with Pandora playing year after year. LOL