MS462 Design Changes

[Mastermind]

Just thinking out loud though, the Mtronic does control the high limit and the mixture right?

What if the Mtronic runs it closer to the RPM / lean limit?

There is certainly a threshold that if you run up against long enough you're going to do some damage.

Pure speculation on my part; just a thought.

The piston skirt wears....then cracks. It's a metal fatigue issue from stress risers out of the notch in the skirt.

 

[qurotro]

Just thinking out loud though, the Mtronic does control the high limit and the mixture right?

What if the Mtronic runs it closer to the RPM / lean limit?

There is certainly a threshold that if you run up against long enough you're going to do some damage.

Pure speculation on my part; just a thought.

The mtronic 462s have limit coil itself I think.

 

[Hundred Acre Wood]

The piston skirt wears....then cracks. It's a metal fatigue issue from stress risers out of the notch in the skirt.

Ok, so it's a metal fatigue issue not induced or exacerbated by an overheat condition. Roger.

 

[Mastermind]

Ok, so it's a metal fatigue issue not induced or exacerbated by an overheat condition. Roger.

I have no "inside information", just makes sense.

 

[Hundred Acre Wood]

I have no "inside information", just makes sense.

Agreed it makes sense. They changed the design for a reason...

 

[huskihl]

The mtronic 462s have limit coil itself I think.

I believe tree monkey found that it’s actually limited by the M Tronic via added fuel, and not spark. I have seen a 261cm start to lean out and scream above the RPM it was running at earlier, which also leads me to believe they aren’t limited by spark

 

[Mastermind]

I believe tree monkey found that it’s actually limited by the M Tronic via added fuel, and not spark. I have seen a 261cm start to lean out and scream above the RPM it was running at earlier, which also leads me to believe they aren’t limited by spark

Agreed

 

[markds2]

The MS462 that I rebuilt (pics of the cracked piston earlier in the thread) has just been brought back siezed. Unusual seizure, two patches exactly 180 degrees opposite each other. Can anyone guess what caused it?

 

[Stevetheboatguy]

The MS462 that I rebuilt (pics of the cracked piston earlier in the thread) has just been brought back siezed. Unusual seizure, two patches exactly 180 degrees opposite each other. Can anyone guess what caused it?
View attachment 361923 View attachment 361924

Just a guess. But looks like over expansion to me. Air restriction caused a overheat? B piston in an A cylinder?

Interesting for sure.


Steven

 

[markds2]

Just a guess. But looks like over expansion to me. Air restriction caused a overheat? B piston in an A cylinder?

Interesting for sure.


Steven

You're on the right track Steven, it did overheat, but not because of the factors you state. Keep guessing

 

[JimBear]

The MS462 that I rebuilt (pics of the cracked piston earlier in the thread) has just been brought back siezed. Unusual seizure, two patches exactly 180 degrees opposite each other. Can anyone guess what caused it?
View attachment 361923 View attachment 361924

Do those have a front/back on the piston ?

Don’t some of those have an arrow or something denoting how the piston goes in.

I don’t dismantle many saws because a short fuse & hammers aren’t conducive to quality chainsaw repairs. Plus I always have parts left over or the saw runs like chit when I am done.

I am happy to stay in my lane & pay others to work on them for me.

 

[markds2]

Do those have a front/back on the piston ?

Don’t some of those have an arrow or something denoting how the piston goes in.

I don’t dismantle many saws because a short fuse & hammers aren’t conducive to quality chainsaw repairs. Plus I always have parts left over or the saw runs like chit when I am done.

I am happy to stay in my lane & pay others to work on them for me.

Being a Strato 2 Stroke the piston is very distinctive in design, and impossible to get backwards, in fact I don't believe the saw would even run.

 

[Wonkydonkey]

I can only guess at a cold 2 corner seizure and a wrong fuel mix ?

 

[markds2]

I can only guess at a cold 2 corner seizure and a wrong fuel mix ?

The fuel did have oil in it (I'm not sure of the ratio or type though) and he had been cutting smaller wood so the saw was well warmed up, it was only when he started doing longer cuts in bigger wood that it overheated and siezed.

 

[Moparmyway]

Got a picture of the top of the piston ?

Is the muffler modded or stock ?

 

[huskihl]

The MS462 that I rebuilt (pics of the cracked piston earlier in the thread) has just been brought back siezed. Unusual seizure, two patches exactly 180 degrees opposite each other. Can anyone guess what caused it?
View attachment 361923 View attachment 361924

Looks like a quickly adjusting mtronic system that doesn’t quickly adjust.

 

[Stevetheboatguy]

You're on the right track Steven, it did overheat, but not because of the factors you state. Keep guessing

If it wasn't air restriction. I'd have to say Kevin is on the right track. Mtron or fuel issue. I thought the mtron adjusted pretty quick. But if the fuel was suspect. It can throw everything off.

Last time I saw a piston like that was someone ran E85 instead of regular.


Steven

 

[markds2]

Got a picture of the top of the piston ?

Is the muffler modded or stock ?

Here you go Kevin, the muffler is stock.

 

[markds2]

If it wasn't air restriction. I'd have to say Kevin is on the right track. Mtron or fuel issue. I thought the mtron adjusted pretty quick. But if the fuel was suspect. It can throw everything off.

Last time I saw a piston like that was someone ran E85 instead of regular.


Steven

You just about hit the nail on the head with that last comment Steven. This saw siezed due to stale fuel. We don't have Ethanol here in NZ (as far as I'm aware) but this guy is in his 70's and buys his fuel 20Ltrs at a time and stores it, un treated with any stabilizer. This fuel had been stored for months like that and it's the height of Summer here, and this is the result. Once the lighter more volatile compounds evaporate, the fuel just burns so much hotter. One sniff of the fuel tank told me the story! This saw has actually had very little run time since I rebuilt it, and I think the new piston was probably hardly bedded in too.

 

[Stevetheboatguy]

You just about hit the nail on the head with that last comment Steven. This saw siezed due to stale fuel. We don't have Ethanol here in NZ (as far as I'm aware) but this guy is in his 70's and buys his fuel 20Ltrs at a time and stores it, un treated with any stabilizer. This fuel had been stored for months like that and it's the height of Summer here, and this is the result. Once the lighter more volatile compounds evaporate, the fuel just burns so much hotter. One sniff of the fuel tank told me the story! This saw has actually had very little run time since I rebuilt it, and I think the new piston was probably hardly bedded in too.

Always amazed at how often people neglect their fuel. But I guess if people paid attention to it like we do. We would be out of work


Steven