Blow up one piston, shame on Stihl. Blow up two pistons, shame on me. Blow up three pistons...?

[pepe_silvia]

After two it was obvious I was doing something wrong, now I know I am.

I bought the saw second hand to use while my other one is getting repaired. The piston (and some other parts) looked brand spanking new.

It made it through a couple hundred bd. ft. of pecan, and then I set to work on the big log I've had laying around, a 3' x 12' elm.

I was cutting 2.5" slabs, so there were 8 or 9 cuts total. She gave out about halfway through the last cut. I'm attaching a picture, but beware, it's ugly.

New meteor piston and cylinder are already ordered.

My mix is about 30:1. I ran probably 10 tanks of that through it. For the last couple of tanks before it gave out, I used my buddy's mix, which he says was 50:1. Went through about a tank and a half of that before she went.

I run it at WOT and let it idle to cool down for around 30 seconds after I finish cutting before switching it off.

I run it for probably, on average, 10 minutes in the cut. My money is on this, I'm just running it too wide open for too long of a period of time.

Any thoughts?

 

[Quietfly]

Yikes ,that sucks!
sorry to see that happen.

 

[big mog]

at 30:1 your running far to lean, I'm surprised you got as long as you did........stihl should be run at 50:1 and properly tuned for the usage

 

[moondoggie]

at 30:1 your running far to lean, I'm surprised you got as long as you did........stihl should be run at 50:1 and properly tuned for the usage

30:1 is rich..... 50:1 is leaner.....

 

[big mog]

someone else who doesnt understand fuel mixes.............30 parts fuel to 1 part oil is leaner than 50 parts fuel to one part oil, the more oil you mix, the leaner the fuel air mixture becomes and the hotter the saw runs, why do backyard "experts" rhink they are cleverer than the people who design the saws and produce the oils to run on specific mixes, if you dont know how to do a basic two stroke mix, perhaps you should take up a new hobby, like crochet or knitting

 

[pepe_silvia]

someone else who doesnt understand fuel mixes.............30 parts fuel to 1 part oil is leaner than 50 parts fuel to one part oil, the more oil you mix, the leaner the fuel air mixture becomes and the hotter the saw runs, why do backyard "experts" rhink they are cleverer than the people who design the saws and produce the oils to run on specific mixes, if you dont know how to do a basic two stroke mix, perhaps you should take up a new hobby, like crochet or knitting

That seems a little harsh, but point taken.

I've read quite a bit on here about guys running with more oil because it keeps things more lubricated and cooler when running wide open.

 

[lone wolf]

What size saw is it?

 

[moondoggie]

someone else who doesnt understand fuel mixes.............30 parts fuel to 1 part oil is leaner than 50 parts fuel to one part oil, the more oil you mix, the leaner the fuel air mixture becomes and the hotter the saw runs, why do backyard "experts" rhink they are cleverer than the people who design the saws and produce the oils to run on specific mixes, if you dont know how to do a basic two stroke mix, perhaps you should take up a new hobby, like crochet or knitting

Dont be a ****

 

[pepe_silvia]

What size saw is it?

MS660. Was running a 42" bar on it this time.

 

[moondoggie]

I understand 30 parts fuel to 1 part oil...30:1 would be richer in oil.....

 

[big mog]

chain type and size, and timber type, type of chain oil, and if running auxillary oiler. and on a 660, good quality fuel and two stroke mix at 50:1 will NOT give problems, I have thousands of hours milling with a 660 on an M7 setup

 

[crzybowhntr]

I understand 30 parts fuel to 1 part oil...30:1 would be richer in oil.....

I hope so. Cause if not I'm losing my mind.

 

[big mog]

the oil fuel ratio is missunderstood by almost everybody, optimun fuel air ratio is around 14:1 to 15:1, this is calculated with a 50:1 fuel oil mix, if you run more oil this fuel air ratio changes, and the burn becomes hotter, this caues the clearances on piston barrel to decrease and seizure to take place, screw around with mixtures at your own cost

 

[big mog]

and for those still confused fuel/air ratios are what are called richer or leaner, not fuel oil ratios.......8 parts airparts air 1 part fuel....rich( typical when choke is on full) 20 parts air 1 part fuel lean....typical when mixed at 30:1 fuel oil mixes

 

[pepe_silvia]

chain type and size, and timber type, type of chain oil, and if running auxillary oiler. and on a 660, good quality fuel and two stroke mix at 50:1 will NOT give problems, I have thousands of hours milling with a 660 on an M7 setup

3/8" pitch, 0.063 gauge, 8 tooth sprocket. Not sure the brand on the chain I was using with the 42" bar. It came in a package deal with the bar. Started with pecan and did some elm as well. No aux oiler, though I had someone pooling some oil on the tip of the bar every couple minutes. Using the generic bar oil from Northern Tool.

 

[pepe_silvia]

and for those still confused fuel/air ratios are what are called richer or leaner, not fuel oil ratios.......8 parts airparts air 1 part fuel....rich( typical when choke is on full) 20 parts air 1 part fuel lean....typical when mixed at 30:1 fuel oil mixes

I get what you're saying. How would I refer to a mixture of more oil to avoid confusion?

 

[Blisters]

and for those still confused fuel/air ratios are what are called richer or leaner, not fuel oil ratios.......8 parts airparts air 1 part fuel....rich( typical when choke is on full) 20 parts air 1 part fuel lean....typical when mixed at 30:1 fuel oil mixes

Yeah man I get it. Lean means not enough fuel too much air... Rich means too much fuel not enough air... Don't have much to do with how much oil is in your gas.

 

[big mog]

if your going to be doing a lot of milling on big dia hardwoods, start looking at a move to stihl pmx chain, 3/8picco, a lot smaller kerf, an 050 gauge, and match it to a GB bars milling bar, uses a lot les power for the same cuts, screw your oiler up to maxand run the thinnest best quality chain oil you can afford, your fuel tank should empty just before your oil one, and on a 3' by 12' elm, 1 cut should be about 1 tank on a 660(sharp chain....very important)

 

[big mog]

the more oil question........doesnt happen...DONT do it, set your saw up carefully

 

[Blisters]

Ppl I have talked to call it fuel & oil mixture. 32:1 40:1 50:1 ...