Carbon Analysis On Piston Crown

[blsnelling]

I'm curious as to whether or not this is normal carbon formation on a piston crown. This is the P&C from my new MS440. It has only seen maybe a dozen tanks of fuel. The saw has not been run excessively rich, or lean for that matter. What's odd is the the combustion chamber and exhaust port are both clean. The carbon on the piston crown was extremely hard and very difficult to remove.

Most of you know that I run Klotz R50 at 32:1. My questions are this. Is this normal? If not, is this the result of running R50? Is it the result of running 32:1? What do the masses think. And please don't just blurt out, oh you're running it too rich. Give me a reason why you think what you do.

 

[REJ2]

I dont know the exact answers your looking for but you could try the next dozen tanks with a different mix and or ratio. I suspect that you definitely suspect that its not right. Wonder what fifty tanks would look like? Too nice a saw for that to continue. REJ2

 

[pioneerguy600]

Brad, why the 32:1? I have always found that carbon build up is from something you are putting into the combustion chamber, usually too much oil or fine sawdust. No scratches on the intake side of the piston so my guess would be too much oil. The intake side of the piston appears to run cooler and the center the hottest.
Pioneerguy600

 

[Arrowhead]

I would try a 50:1 mix. Clean it up completely and run Stihl 50:1 for the same amount of tanks and see if it makes a difference.

 

[blsnelling]

In order to pin down the source, I think I would need to only change one thing at a time. Do I change oils or ratio first? I'm nearly out of R50 anyway and have lots of Woodland Pro Synthetic. I have thought of running it a 40:1 though. The saw will be ported though. That's why it's apart. The thing of it is, I'm seeing this on all of my saws that I tear down.

 

[FATGUY]

even your ported saws look like that?

 

[luvsaws]

What gas do you run?

 

[indiansprings]

Brad, I would personally think this is way abnormal for the amount of use/fuel you've run through the saw. I"ve torn down much older/used saws with a fraction of that build up. I think it may be the 32:1, don't know about the Klotz, I'm sure it's good stuff. I would clean it up like new, and run either Woodland Syn or Ultra at 50:1 and see what it looks like after the same amout of tanks. I think based on what I've seen with my saws, that you won't have a fraction of that build up. What does the arrestor screen look like if it is still using one. I would be concerned about that much build up in such a short period of time myself.

 

[mtngun]

Nothing wrong with 32:1, many CSM'ers use 32 or 40:1, yes we get some carbon build up. Only thing unusual in your case is the build up on the piston but not the chamber.

Other than the obvious, I'm wondering if the piston was a little hot ? That might explain why the carbon baked onto the piston but not the chamber.

Didn't you mention a while back that you had a case of WP synthetic ? How 'bout this: clean up the piston, run a dozen tanks with 32:1 WP synthetic, and report back.

 

[dingeryote]

Also take a gander at the Fuel itself.

"Winter blend" gasoline has a rather nasty buch of chemicals added to maintain EPA emissions compliance, and may be conspiring with the R50 in an undesirable manner.

That IS wierd.

See what happens with summer gas after the same number of hours maybe?

Stay safe!
Dingeryote

 

[7sleeper]

I have no idea and am no saw tech but I have just started to take my saws apart. I am wondering if this is of any importance that the cylinder seems to be unevenly worn at the bottom.

Compared to the other side

Of course if you have this with all your saws I would believe that the oil is the culprit.

7

 

[dingeryote]

In order to pin down the source, I think I would need to only change one thing at a time. Do I change oils or ratio first? I'm nearly out of R50 anyway and have lots of Woodland Pro Synthetic. I have thought of running it a 40:1 though. The saw will be ported though. That's why it's apart. The thing of it is, I'm seeing this on all of my saws that I tear down.

All on the same fuel bought from the same place over the last several months?

Stay safe!
Dingeryote

 

[albert]

Looks like the piston is getting too HOT. Baked oil under side and baked or discolored above the exhaust side top ring. I would try the wp synthetic @ 40 or 50:1 What fuel are you using. Looks like the transfers need to be evened up.

 

[04ultra]

2008 model 7900 Mobil 2T at 50-1 about 200+ tanks ports are clean.........93 octane non eth ......





.

 

[Gumnuts]

Pretty sure you would be meticulous with your settings and mix....but /
You say new / 10 tanks.
Have you really put her to work yet ? Is she ported yet /cyl ?
Just thinking she has only done short runs ,dare i say, often, not a full throt.
Was run in.... rich ,to long ,before re-setting.
Does look excessive even if. .02

 

[blsnelling]

even your ported saws look like that?

Yes. Maybe not as much, but still the same kind of carbon formation.

What gas do you run?

Shell Premium Unleaded.

What does the arrestor screen look like if it is still using one.

I removed it right away.

I'm wondering if the piston was a little hot ? That might explain why the carbon baked onto the piston but not the chamber.

No signs of heat on the bottom side

Didn't you mention a while back that you had a case of WP synthetic ? How 'bout this: clean up the piston, run a dozen tanks with 32:1 WP synthetic, and report back.

I think I like that idea, although I may cheat and go to 40:1.

I am wondering if this is of any importance that the cylinder seems to be unevenly worn at the bottom.

I see that on the bottom of the intake skirt on nearly every saw I tear apart. Matter of fact, this is less than normal. Not an issue, IMHO.

All on the same fuel bought from the same place over the last several months?

For the most part. Always Premium Unleaded.

 

[blsnelling]

Pretty sure you would be meticulous with your settings and mix....but /
You say new / 10 tanks.
Have you really put her to work yet ? Is she ported yet /cyl ?
Just thinking she has only done short runs ,dare i say, often, not a full throt.
Was run in.... rich ,to long ,before re-setting.
Does look excessive even if. .02

I took it easy for the first few tanks, but have run it hard since then, as you would any saw. Even when I had it a little rich for breakin, it still cleaned up nicely in the cut. I never had it blubbering rich. Since break-in it has not been babied. It's always had a 28" B&C on it and has seen lots of buried cuts in Oak. Lots of full throttle extended cuts.

It has only had a muffler mod to this point. It's apart for porting.

 

[Sprintcar]

Brad,

This is the piston I removed from an 084 that always ran at a 50/1 ratio. He swore that he always made sure the saw got only Stihl oils, until one of his employees straight gassed it. The carbon build up in comparison to the 440 piston you have shows a considerable difference.

Hope this helps.

Jerry

 

[woodgrenade]

For everybody else who is running 32:1 is it done using a full synthetic? I'm thinking that maybe the high oil ratio in addition to the extra cooling properties of the synthetic are leading to the excess carbon on the crown of the piston.

If you are seeing it in all of your saws ported or not I would have to say eliminate one variable at a time just like you proposed. Either change the mix, or the oil type, but not both at once.

 

[stihlboy]

did the wiesco pistons get deposits? i have seen deposits like that but they were on saws used alot more. it might be that it is 32:1,.

hard to tell, im interested in the findings