A little bit of STRAIGHT GAS!!

[parrisw]

My best guess is that, those cranks like the one I posted a pic of that are all blue looking, held together longer before they locked up causing the major overheat of the bearings. The one today doesn't look blue, I'm guessing it failed rather quickly, and locked up.

 

[tree monkey]

if there is oil on the piston then there has to be oil in the case as well.

if the piston was scored then yes the bearings can also fail from straight gas.
i beleave you said the piston had oil on it. it has to go in the case to get to the piston.

if there is no sign of scoring on the piston i find it hard to beleave it was caused from his premix.

lets say the premix was 100/1 and the bearing was starved for oil.it then should show signs of heat. the piston should also show signs of a lack of oil. the spark plug should nearly white as well.

 

[parrisw]

if there is oil on the piston then there has to be oil in the case as well.

if the piston was scored then yes the bearings can also fail from straight gas.
i beleave you said the piston had oil on it. it has to go in the case to get to the piston.

if there is no sign of scoring on the piston i find it hard to beleave it was caused from his premix.

lets say the premix was 100/1 and the bearing was starved for oil.it then should show signs of heat. the piston should also show signs of a lack of oil. the spark plug should nearly white as well.

The oil I saw, was only on ridges. Like on the side of the piston at the pin, on a ridge in the case. The spark plug was a very light grey colour.

 

[Jacob J.]

lets say the premix was 100/1 and the bearing was starved for oil.it then should show signs of heat. the piston should also show signs of a lack of oil. the spark plug should nearly white as well.

It doesn't always happen that way though. The modern Huskies are notorious for being susceptible to blowing out the big end rod bearing even on 50:1. This is why all the timber cutters I know (including me) that run Huskies run 'em on 40:1/32:1.

 

[tdi-rick]

Will, bearings can just fail, either because they just aren't the best or from an over rev.
It appears, as Tree Monkey suggested there is still residual oil there and no real signs of distress ? but I'll demure to JJ's much, much greater experience than mine.

I do remember my old kart engine builder was pedantic about the bearings used in anything that spun 15-18,000RPM under load, and with an aftermarket crank we really don't know what we are getting. Back then he would only use Thompson little ends and 'poofter bearings' for the mains (FAG)
Can't remember the big ends, either FAG or INA ??
Anyway, lesser quality bearings would spontaneously let go.

The other thing that will lead to bearing failure is too much radial clearance, poor geometry of the halves when pressed together (not square) rod twisted, etc.
All hard to know unless you measure and build up the bottom end yourself.

Anyway, great thread, back to the discussion.

 

[Jacob J.]

I have to interject the opinion that I've run into many modern FAG bearings in chainsaws that weren't that great, with FAG having been an OEM supplier to both Stihl and Husqvarna...

 

[parrisw]

Will, bearings can just fail, either because they just aren't the best or from an over rev.
It appears, as Tree Monkey suggested there is still residual oil there and no real signs of distress ? but I'll demure to JJ's much, much greater experience than mine.

I do remember my old kart engine builder was pedantic about the bearings used in anything that spun 15-18,000RPM under load, and with an aftermarket crank we really don't know what we are getting. Back then he would only use Thompson little ends and 'poofter bearings' for the mains (FAG)
Can't remember the big ends, either FAG or INA ??
Anyway, lesser quality bearings would spontaneously let go.

The other thing that will lead to bearing failure is too much radial clearance, poor geometry of the halves when pressed together (not square) rod twisted, etc.
All hard to know unless you measure and build up the bottom end yourself.

Anyway, great thread, back to the discussion.

Ya, that's just the thing. I can't answer all of those questions. So we'll never know the whole story. One thing I know for sure, is there is something up with his mix. So I'm going to have to go with that for now. And if there was a flaw with that crank, it would of likely failed much sooner then it did.

At any rate, its far out of its warranty period. LOL

 

[parrisw]

I have to interject the opinion that I've run into many modern FAG bearings in chainsaws that weren't that great, with FAG having been an OEM supplier to both Stihl and Husqvarna...

I've put man FAG bearings in auto's too. And I can say as well, that they aint nothing special.

 

[tdi-rick]

Interesting, they were the bearing to use in Parilla and PCR kart engines twenty something years ago.

I wonder if they supply different grades/finishes ? Apparently Timken do, so i've been told.

 

[Jacob J.]

FAG was a supplier to McCulloch back in the day. I've pulled many an old FAG bearing out of Mac saws and they were high quality back then. There were very few main bearing failures in the old Macs.

 

[tdi-rick]

Actually, FAG have a few factories in the Far East now, (who doesn't ?) they took over one in Korea some years back after selling them machines and then the Korean company started to go under.
IIRC they merged with INA a little while back too.

Sorry fella's, getting a little OT here :monkey:

 

[Hddnis]

I rebuilt a straight gassed 029 that had the big rod bearing fail without discoloring the metal. Very lightest bit of rubbing on the exhaust side of the piston and that was most likely caused by carbon buildup. There was still oil under the rings and on the intake side of the piston.

It really does stand to reason; the little rollers will get hot long before the the mass of the connecting rod gets hot. If the damage is done to the rollers and then the saw is shut down before the heat can get real high in the rod you will see exactly what we see in this saw.



Mr. HE

 

[bonden]

It doesn't always happen that way though. The modern Huskies are notorious for being susceptible to blowing out the big end rod bearing even on 50:1. This is why all the timber cutters I know (including me) that run Huskies run 'em on 40:1/32:1.

I run all my Stihl saw`s on 50:1 and never have any problem with it, the gas i use in Norway are 95 or 98 octane that i mix with synthetic 2 stroke oil. (this don't include the modified saw`s i have).

 

[little possum]

ha ha ha. You never heard that saying before!! LOL!

That was a new one for me too, so thats why I repped you for a good laugh


Anyways, the Husky failed, where are the bashers? opcorn:

 

[Cantdog]

but that sucker is locked tighter then a skunks A55hole. QUOTE]


HAHAHA!!! Being from the Atlantic coast and a lobsterman's son, we have a slight variation on this.

As my late father would always say "tighter than a crabs a$$ and that's water tight!!"

On the subject of your problem big end bearing here's my $0.02 worth, this bearing shows no sign of heat related failure (no blueing), the fuel you show certainly doesn't look to have any or little oil in it. However as said you will have to find out just what these guys use for oil it may not have any dye added, doesn't seem likely but... This failure could be from a number of reasons, snapped roller, cracked cage or perhaps another piece of foreign metal/material entering the bearing. Any thing that happens to that bearing at 15,000 rpm and it's over. The absence of signs of heating tells me it was sudden catastrophic bearing failure not a lean seize which will take at least a few revolutions to destroy itself. This puppy stopped right now. You might ask the operator what was the he doing when this occurred, idling, reving no load, cutting under load, limbing etc. Just to get an idea what conditions the saw was operating in at the actual time of failure. Good luck.

 

[Freehand]

That's what I think??? There was a coating of oil on the piston?? Maybe there was enough left over to give it a little lube, who knows???

My theory on the colour of the gas is that, there was a little mix left in the saw tank, he then filled it with straight gas, mixing a little with what was left in the tank, giving very little lube, but not enough for the big end to survive. My first question to him tomorrow will be what kind of oil do you run? If he says husky or stihl?? Then it should be blue gas mix right? I'm assuming both those oils are blue, almost every 2stroke oil I seen is blue. The **** I took out well, you can see.

He went old school and mixed it up with thirty weight if there is indeed ANY oil in that mix.I've seen mix in blue,red,and purple....never clear/amber.

You should get the operator to fess up.opcorn:

 

[Steveo_supremo]

There are 2 stroke oils available that aren't dyed. Mobil 1 MX2T is not dyed. They stopped making it a couple years ago, but there is still plenty of it left out there. Also, the Ski-Doo branded oil that I run in my sled has no dye in it.

 

[THALL10326]

Ya, I haven't told him yet, I'll call him tomorrow. I'll let ya know how the story plays out.

Oh great saw wrench Tom. Have you seen a bottom end seize up before scoring the piston and cylinder?? The piston and cyl in this is untouched??? Unless it had a 4 corner seize or something?

No, can't say I have. The bottom end is usually ok even thought the top end is shot. Course now on pure gas the bearing may as well be running dry, no oil so I guess it could happen, those bearings need that lube.....

 

[Metals406]

Bearings can be softened before they reach a blue or purple color.

Color on steels are an indicator of temperature. If the bearings were already poor quality, and their material is of a lower grade, and their hardening and tempering processes are lacking. . . 480 degrees can be detrimental, and cause failure.

This on top of an already poorly made (from a metallurgical standpoint) bearing.

As you can see from this chart, the blues and purples are dang hot.

 

[isaaccarlson]

I still say he broke a roller....

something happened to that bottom end That bottle looks like it has some kind of oil in it. The light looks different