TRI955
I'm the man in the box
I would think if you just would back the H and L needles off just a bit, it would be better for the saw...
Carbon Analysis On Piston Crown
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I would think if you just would back the H and L needles off just a bit, it would be better for the saw...
2000ssm6
Stihl User
I've been running 50:1 Stihl Ultra/93 in all my saws, even the ported ones. 32:1 is just too much oil imo.
I'm thinking your right.
wigglesworth
Booned
Is it just me or does that plug looks weird? The center electrode looks like it was slightly lean, as it's a more gray than brown, but the outer looks like it was rich as crap. :dunno:
I thouht the same thing. It's not a light grey like I would expect if lean, but it's not brown either. But the outer section looks crazy rich.
dingeryote
Blueberry Baron
Brad,
Just for purposes of edumacatin my dumb self..
Wouldn't the additional combustable fuels energy offset any losses in blowby when running 50:1 over 32:1?
Conventional wisdom is that the more of the highly expansive stuff you can get in there, the better, and is why folks started tinkering with 100:1 back when Bel-Ray was the big dog on the MX scene.
Stay safe!
Dingeryote
Just for purposes of edumacatin my dumb self..
Wouldn't the additional combustable fuels energy offset any losses in blowby when running 50:1 over 32:1?
Conventional wisdom is that the more of the highly expansive stuff you can get in there, the better, and is why folks started tinkering with 100:1 back when Bel-Ray was the big dog on the MX scene.
Stay safe!
Dingeryote
You make a valid point. I was just discussing that with another member on the phone.
I see a significant amount of wet deposits on the threaded barrel of your plug. I run Shell Super as well. but it says specifically that there is no ethanol in it. I run Ultra at 45:1, and have never noticed any carbon buildup. In fact, I think it dissolves existing deposits, as i sometimes see black liquid around the muffler. I know nothing about Klotz or any other oil. I think Ultra is the right oil for my saws. Your piston crown shows a geat deal of hard deposits, which seem as though they could be from excessive carbonaceous material (oil) burning at very high temps (modded saw, very high rpms). Andy used to say that a richer oil ratio actually leans out the mixture, because the relative fraction of fuel is lower in the mix. Add to that the leaned out hi screw to obtain higher than factory recommended max WOT rpms, which you consistenlty report on your mod projects, and it could simply be a matter of excess oil being carbonized. I just changed the oil in my air compressor this evening, and the IR syn oil bottle said that dirty cooling fins cause excessive temperature and subsequent oil temps, and oil carbonization on the moving parts. That is with no combustion, just heat from the compression of air. So maybe it is a simple matter of lightening up the mix, or, you told us not to say it, but you may just be running it too rich.
I wonder if race car engines carbonize like that due to the higher output of the modified engines. Maybe hard mods require more frequent teardowns in saws as well.
I wonder if race car engines carbonize like that due to the higher output of the modified engines. Maybe hard mods require more frequent teardowns in saws as well.
stihl86
Addicted to ArboristSite
Or the oil you use isn't all it's cracked up to be. I've never seen the need for synthetic oil in a saw, as long as you use Stihl H/P. Stihl came out with Ultra for the 4-Mix (BR600 has to use it) and has been on a sale blitz with it since. Carbon is never an issue with saws when mixed at 50:1, with at least 89 octane. Many will disagree, and that's fine.
dingeryote
Blueberry Baron
Teacherman,
Look at Brads spark plug. I was thinking the same as you untill I saw the insulator on that plug. The gunky mess is on the plug but where it shoud be about the same temp as the combustion chamber, and not on the insulator where temps would be cooler.
Makes me think that it's non comustible additives in the fuel,oil, or both that are baking on the aluminum and steel.
Kinda like the "Lead replacement" additives do when ya have a brain fart and put it in the wrong can.
It's wierd any way ya look at it.
Stay safe!
Dingeryote
dingeryote
Blueberry Baron
Not trying to make a point, just wondering.
We did a lot of dinking around in the transition from air cooled to watercooled 2 strokes back then, and LOTS of wives tales are still swirling around as gospel.
I can see where a thicker film or higher film strength, would lead to better ring seal, but how much?
LOL!!
It's all academic to me cuz I don't race anything but myself anymore.
Just wondering.
Stay safe!
Dingeryote
BIGBORE577
Addicted to ArboristSite
2008 model 7900 Mobil 2T at 50-1 about 200+ tanks ports are clean.........93 octane non eth ....
Same here, I would suspect too rich at 32:1, or crappy oil. Forgive me, recently I've been working with vintage saws that ran ratios as low as 16:1 with the crummy dino oil available at the time, with the same results Brad has had. After cleaning them up and running them with 50:1 Mobil 1 or Motul 800, I no longer have the same problems. Their P&C's remain very clean, nothing like pictured, even being as old as they are.
little possum
Crash and Burn
JMO, I think your running too rich of mix. We run 50/1 93 or AV, and dont see that kind of buildup. There is a 044 that was used hard in the woods for numerous years with 50/1 and AV, and the p/c are pristine.
WHERE IS GARY?!?
WHERE IS GARY?!?
Brad, were your first tanks the R50 @32:1??
Gumnuts
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Interesting - suggests use the higher ratio for the Kroll....but you been using Kroll for a while now.....worth checking other workers ???
Similar.....work saws running Stihl / Mobil 2 T @ 30-35 / 1 mimimal build up
from 20 tanks .
I can tell you why I think the piston crown has so much carbon buildup.
First it's not the oil ratio......... It's because your running a ester based racing oil that has little to no detergents in the additive packaged, and it has a very high flash point + we have crappy fuel. Brad it also looks like the piston crown got a little hot, I know how you like to tune your saws.
With that said I've been test running a few different oils the past month or so. The reason for this is because I've also found a bit more carbon buildup than I'd like to see. I ran Echo power blend at 32:1 for years and I never saw any excessive buildup on the piston crown like I have with R50. However when I ran echo's oil the piston skirt, combustion chamber and piston rings would never look as clean as they do with R50. Check out the piston on my 7900 it looks new, and I've ran nothing but R50 at 32:1 since day one.
BTW I do not recommend running super techniplate in a non race application as it is known to have poor corrosion resistance.
First it's not the oil ratio......... It's because your running a ester based racing oil that has little to no detergents in the additive packaged, and it has a very high flash point + we have crappy fuel. Brad it also looks like the piston crown got a little hot, I know how you like to tune your saws.With that said I've been test running a few different oils the past month or so
. The reason for this is because I've also found a bit more carbon buildup than I'd like to see. I ran Echo power blend at 32:1 for years and I never saw any excessive buildup on the piston crown like I have with R50. However when I ran echo's oil the piston skirt, combustion chamber and piston rings would never look as clean as they do with R50. Check out the piston on my 7900 it looks new, and I've ran nothing but R50 at 32:1 since day one.BTW I do not recommend running super techniplate in a non race application as it is known to have poor corrosion resistance.
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Nitroman
Addicted to ArboristSite
The patterns you are seeing are called "piston wash", a term you'd see very often on snowmachine racing forums, where wash is as important as the plug color in determining the correct jetting for the snogo for the given conditions.
From looking at the pix, you are jetted nicely. Is this the same saw you showed the coffee colored plug a few months ago? If so you are dead on.
I just saw the photos of your plug. You are dead on. The carbon building up is because the saws aren't running full throttle all the time, and as such are running cool. If you want to get a really accurate plug reading, run the saw in a cut for as long as you can at full throttle, then shut it off while still in the cut, at full throttle. Do not let it idle. You want to see what the plug and piston look like when they are hot. Prolly try to find a log you can saw in half so you can run the saw for 1-2 minutes to burn off all that carbon on the plug. Won't happen on the piston though, but you'll see what it all looks like.
Go here for some good photos of lean, rich, and correct jetting:
http://www.bikemanperformance.com/tech_detail.php?ta=4
The fellow who showed the badly scuffed piston will find his under "lean photo".
From looking at the pix, you are jetted nicely. Is this the same saw you showed the coffee colored plug a few months ago? If so you are dead on.
I just saw the photos of your plug. You are dead on. The carbon building up is because the saws aren't running full throttle all the time, and as such are running cool. If you want to get a really accurate plug reading, run the saw in a cut for as long as you can at full throttle, then shut it off while still in the cut, at full throttle. Do not let it idle. You want to see what the plug and piston look like when they are hot. Prolly try to find a log you can saw in half so you can run the saw for 1-2 minutes to burn off all that carbon on the plug. Won't happen on the piston though, but you'll see what it all looks like.
Go here for some good photos of lean, rich, and correct jetting:
http://www.bikemanperformance.com/tech_detail.php?ta=4
The fellow who showed the badly scuffed piston will find his under "lean photo".
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Nitroman thank you for the link.
One thing to remember carbon buildup is normal, and honestly to me Brads 440 piston doesn't look all that bad.
Gypo Logger
Timber Baron
It's gotta be the fuel and not the mix. If a saw is run WOT on 32:1 and set up to factory specs max rpm, there should be no carbon, especially with a muff mod. The mix cannot be suspect as all 2 cycle oil is good. Must be the fuel.
John
John
I say its the oil not burning off and baking on to the hotter parts of the piston. You can really see where your transfers blow across the crown and intake side of the piston and keep them clean. I would switch oils and maybe go to 40:1 after the porting and see what happens. I have a worked over 044 that has about the same number of tanks through it and the ports and crown are all very clean with almost no buildup but they do look a little wet at times cause I tend to be idling between cuts and run a little rich
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