What oil ratio were you running when your saw blew up

[John Lyngdal]

One of those curly ears broke off one of the wrist pin retainers. Had nothing to do with the oil. Kinda weird though.

Just finished rebuilding a shelf queen Stihl 034 that ate one of its wrist pin retainers. The piston took the brunt of damage and the otherwise immaculate cylinder was scored below the intake port.
Before this incident I liked the wrist pin retainers with the "ears" as they are easier to install and remove, but I've had a change in heart.

 

[ironman_gq]

I've got a pallet of demo saws blown up by "neck down" guys, most had something resembling gas mixed anywhere from rinsing out the oil bottle to pouring a whole bottle in the tank and couple that thought they were diesels. Most common failure is as you would guess a full on piston skirt to cylinder wall weldment and resulting lockup. A few died from too much concrete dust in the air and a couple died from seals failing due to concrete dust.

 

[Chainsaw Jim]

50:1 will let meltdown occur sooner than a heavier ratio when there is anything causing it to overheat. Dull chains with tall rakers cause overheating too.

Typically 50:1 causes pto bearing failure in hotrod saws like the 562 or ported saws. What causes meltdown usually occurs at any ratio.

 

[Bwildered]

Out of the literally hundreds of saws that have been melted or blown up & shown in posts on this forum, I find it interesting that only 7 people have been upfront & done the poll, if 50:1 mix had been involved they would have been coming out of the woodwork to bag it, the real truth is in the omissions!
Thanski

 

[Rockjock]

Out of the literally hundreds of saws that have been melted or blown up & shown in posts on this forum, I find it interesting that only 7 people have been upfront & done the poll, if 50:1 mix had been involved they would have been coming out of the woodwork to bag it, the real truth is in the omissions!
Thanski

For me what is most interesting is that I was at a Tech class and I asked the instructor this very question and he had to admit that in his experience the mix ratio was not the factor to killing saws. Bad fuel, leaky seals and not running a saw under load were the main reason they blew up. The rest of the class chimed in and they all agreed with the instructors assessment. We are talking about 50 guys with 20-30 years at a bench each . But it sure does make an interesting conversation over some cold ones.

 

[Full Chisel]

Higher oil ratio can potentially cause an engine to run hotter if the carb isn't adjusted properly...the resulting lower fuel ratio reduces evaporational quenching which is the primary cooling mechanism in a two stroke engine.

That said...I'll take the extra insurance of 40:1 or 32:1 and keep the bearings happy.

 

[HarleyT]

But it sure does make an interesting conversation over some cold ones.

What? You're a mortician????

 

[Wood Chopper]

Been running Amsoil saber in all our saws at 80:1. [emoji102]. Are certain oils better than others? Probably. But none by themselves are going to cause catastrophic failure. ????


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[67L36Driver]

32:1

Saw #1 stopped short when a rod bolt backed out. Homie XL-101.
Saw #2 stopped when the piston skirt disintegrated. Pioneer P-21.

Nothing to do with oil at all really.

 

[Rockjock]

What? You're a mortician????

Not officially , I am often telling people to get stuffed.

 

[Deleted member 149229]

Try this reason from a 40 year machinist. When I started in the late 70's +/- .001" was a tight tolerance, when I retired Jan. of this year we were working +/- 1 micron. The tighter the tolerances EVERYTHING must be close to perfect. Any foreign object that might scratch metal with "old school" tolerances will destroy new tolerances because there isn't room for any type of object. We've had locomotive engines fail because a dime sized piece of Ionbond coating delaminates that was only 2 microns thick and caused a wrist pin to seize up. Tighter tolerances mean higher performance but also contribute to higher failure rates. Seen old engines come in that were 20 years old and had valve seat recession of over 1/2" and still running.

 

[Charlie Pendleton]

I've found mixing fresh gas, being anal about clean air filters, greased filter bases, and $50 for a meteor kit and oem bearing every other season saves money on cylinders, crank bearings etc.
Do they need replaced? Probably not but maintinance is cheap insurrance.
I do mix 40:1 though

 

[HarleyT]

oem bearing?

 

[Charlie Pendleton]

oem bearing?

Oem husky or stihl upper rod/wristpin bearing.

 

[HarleyT]

Is this aftermarket "kit" a piston assy? Or piston/cyl?

 

[Charlie Pendleton]

Is this aftermarket "kit" a piston assy? Or piston/cyl?

I just order an aftermarket meteor piston kit, comes with piston, rings, pin and clips. I run over to the dealer and buy the factory bearing because its readily available.

 

[HarleyT]

What model are we talking about?

 

[Charlie Pendleton]

I run a 372, 555 autotune, 056av, 076 super and a ms290 spare saw for the wife or sawless buddy.
The 076 gets a piston much less as i don't use the hog as often.
Was that your question?

 

[HarleyT]

So you replace the piston every other year in all of those saws, whether it needs one or not? And bearing?

 

[Charlie Pendleton]

So you replace the piston every other year in all of those saws, whether it needs one or not? And bearing?

My go to saws yes, why not?
The 076 not so much its not used as often. The 056 got a piston when i bought it a month ago since it was new to me and i don't know if it was done.
I grew up on 2 stroke bikes, we replaced the pistons every year if they needed it or not. When a Piston wears around the skirts or wherever and finally breaks it generally takes out the cylinder, can break the rod and even crankcases. Peices of metal fall into the lower bearings and can never get fully cleaned out without disassembling and splitting the cases. My thoughts are why bother with any of the risk and just rebuild them.