Carbon Analysis On Piston Crown

[7sleeper]

..
I have always used 20:1, ....
Try a few months with a leaded gas like Sunoco standard.

WTF!

I can really smell it. If this thread goes on any further we will all be using 8:1 with dino oil pretty soon, and be happy about the zero carbon!

7

 

[Miles86]

Yes, it does smell good, but not as good as Benol.

 

[huskystihl]

Hey Brad if you read this I had some extra time so pulled my 260 apart knowing for sur it's the only saw I have that has never seen anything but amsoil since new outside of my 200. Most of my other saws have probably seen ultra but anyhow the 260 is modded and no carbon buildup anywhere. Please don't think this is an amsoil plug but my 460 before it got crushed was nothing but stihl oil and was carboned just like the one in your photo. I know you mentioned amsoil as a possability so maybe this helps. For what it's worth there was some buildup on the crown on my 372 which has since cleaned up after switching.

 

[StihlyinEly]

Hey Brad if you read this I had some extra time so pulled my 260 apart knowing for sur it's the only saw I have that has never seen anything but amsoil since new outside of my 200. Most of my other saws have probably seen ultra but anyhow the 260 is modded and no carbon buildup anywhere. Please don't think this is an amsoil plug but my 460 before it got crushed was nothing but stihl oil and was carboned just like the one in your photo. I know you mentioned amsoil as a possability so maybe this helps. For what it's worth there was some buildup on the crown on my 372 which has since cleaned up after switching.

I've swapped a number of used saws over to Amsoil from conventional and have seen the cleanup first-hand. Same thing with two gas-powered ice augers that were carboned up and one outboard. And no, I'm not making this an Amsoil ad either. I don't doubt there are plenty of other synthetics with cleaning characteristics out there.

And, lastly, no, I'm not an oil expert. But I did stay at a Holiday Inn Express last night.

 

[blsnelling]

Thanks guys. I'm still reading

 

[huskystihl]

I've got a 2 stroke mini tiller that I use for in between the rows in the garden out at the shop. Long story short I have a whole case of the husky white bottle oil that a rep gave me one day so I use it for weed whips and snowmobiling for the kids "No their not nice sleds". Anyhow the muffler vibrated off this thing last year and a quick peak in the jug and the crown looked like I hit it with a blow torch, so I for the heck of it pulled it in and put the muffler on and did a compression test which floored me at 180lbs. The garde we use it in is 30x60 so it runs for about 3hrs at a time all summer so it isn't a once in awhile thing. I wouldn't worry about it unless it causes problems

 

[Danger Dan]

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.

FWIW...Carbon seems to be heavier on the right side.
- Suggests xfers might not be firing simultaneously or the angle is off on the right side, because the piston crown is not being swept.
- You stated it's a new saw, but has it been modded?

 

[Andyshine77]

The saw was stock except for a muffler mod, the saw is now ported and running different oil at 32:1. After the saw gets some time on it, Brad's going to inspect it to see how the new oils running.

 

[Stihlman441]

BCMs answer was to not run premium unleaded or mid range unleaded road gas because of the deposits it leaves behind. Regular unleaded did not do this any where near as much. The techs would laugh when tearing down a motor and say "Oh yeah another Hi-test guy"
I was not advocating "special" gas for saws. As I said I've changed my thoughts on this subject completely. I used to run all 2 strokes rich on oil because that's the way my father taught me. Now I see over oiling as more of a danger than a help. It is an attempt to "save something to death" How many pistons have you seen with a big ugly score from a carbon chip that broke free and got wedged between tha piston and cyl wall. Carbon buildup is not good for any motor and it will not reach a point and stop building up. Carbon will adhere to itself better than anything else. In a water cooled 2 strokes it will eventually lead to "coking" which is a term used to describe severe carbon formations which will cause your rings to seize, break and you know the rest of scenario. Carbon is the "killer" of 2 strokes. I just thought it interesting that the guys "in the know" who routinely build and race 160 Horsepower, 180 MPH 2 cylinder motors would recommend a lesser grade of gas to help solve the carbon issue.

This is interesting,i had a chat to a stihl dealer saw tuner the other day about blow bye on a couple of my saws.I have always used premium unleaded fuel and Mobile 1 racing 2T at 40:1.He said that's the problem (premium unleaded) the saws are designed to run on 90 oct fuel and that the high energy fuels do more harm than good.

 

[robertjinnes]

oil sealing rings to increase compression

In one of your early responses, you indicated running 32:1 to get oil sealing compression increase in the hope of more power. Oil hurts combustion. When I corrected valve stem seal leak by. Fuel to oil ratio went from approx 150:1 to 600:1. I got a 10% increase in fuel economy. Simply better burning of the gas without oil. Same only more severe is occurring with 32:1. Synthetic oils have higher temperature capabilities. In other words, they won't thin out or burn as easily as Dino oil. Drop back to 40:1 or even recommended 50:1 since saws are generically capable of reaching very acceptable total life hours running 50:1 Dino.

GOOD LUCK. REPORT what we all hope successful resolution.

 

[blsnelling]

I'm still not liking what I'm seeing with R50 at 32:1. This is my NE 346XP. It turns north of 16K RPMs and is not babied at all.

As discussed before, once I'm out of R50, I'm going to all K2, still at 32:1. I'm already using it in my 440, and initial indications are that it is burning cleaner.

 

[tdi-rick]

This is interesting,i had a chat to a stihl dealer saw tuner the other day about blow bye on a couple of my saws.I have always used premium unleaded fuel and Mobile 1 racing 2T at 40:1.He said that's the problem (premium unleaded) the saws are designed to run on 90 oct fuel and that the high energy fuels do more harm than good.

A dealer here recently told me that Honda are recommending only standard unleaded here in their four strokes, particularly mowers, that 98 PULP is leaving too many deposits ?
The mowers in particular aren't working very hard, and so the deposit formation.

 

[robertjinnes]

32:1 oil mix

It appears that the piston head has dry soot while the squish area of the cylinder at the intake side is wet oily. If that is correct as expected the piston is running hotter than the cylinder. Why did you pull it apart? Just your curiosity? If you're into build and teardown, clean the carbon off and run a a few tanks at 40:1 and pull it down again. If it is substantially cleaner- just too much oil @ 32:1. If it is still carboned, especially on the piston head, possibly gas rich. Either way--rich on fuel means extra extra oil or OK adjustment on fuel means just extra oil. Either way means you shouldn't score a cylinder etc.
We certainly can't expecting a 2 stroke to burn as clean as a 4 stroke.

Are you hoping to optimize oil VS power output without trashing cylinder and piston? 16K + certainly requires good lubrication.

Good Luck.

 

[tdi-rick]

In one of your early responses, you indicated running 32:1 to get oil sealing compression increase in the hope of more power. Oil hurts combustion. When I corrected valve stem seal leak by. Fuel to oil ratio went from approx 150:1 to 600:1. I got a 10% increase in fuel economy. Simply better burning of the gas without oil. Same only more severe is occurring with 32:1. Synthetic oils have higher temperature capabilities. In other words, they won't thin out or burn as easily as Dino oil. Drop back to 40:1 or even recommended 50:1 since saws are generically capable of reaching very acceptable total life hours running 50:1 Dino.

GOOD LUCK. REPORT what we all hope successful resolution.

I know your post is a few months old, but it has been shown time and again that higher oil ratios in a two stroke = more power, the supposition being better ring seal.

Racing air cooled two strokes still mainly use 16-25:1 oil/fuel ratios, even when using 'exotic' oils like Elf HTX909, Castrol XR77, etc.
1. to stop seizing.
2. makes more grunt.

 

[tdi-rick]

It appears that the piston head has dry soot while the squish area of the cylinder at the intake side is wet oily. If that is correct as expected the piston is running hotter than the cylinder. Why did you pull it apart? Just your curiosity? If you're into build and teardown, clean the carbon off and run a a few tanks at 40:1 and pull it down again. If it is substantially cleaner- just too much oil @ 32:1. If it is still carboned, especially on the piston head, possibly gas rich. Either way--rich on fuel means extra extra oil or OK adjustment on fuel means just extra oil. Either way means you shouldn't score a cylinder etc.
We certainly can't expecting a 2 stroke to burn as clean as a 4 stroke.

Are you hoping to optimize oil VS power output without trashing cylinder and piston? 16K + certainly requires good lubrication.

Good Luck.

Yep.

If the skirt looks OK I wouldn't worry too much, the oils main job is to keep things going up and down and round and round smoothly.
Cleaner burning is a bonus, as soon as you modify an engine to pull those sort of revs, stopping seizing is the name of the game.




Brad, if you like my 7901 will be coming apart soon and it's had a diet of 98RON fuel and Motul 8002T OR @ 40:1.
I'll post the pictures of the piston and chamber in this thread.

I know the boys that are running Maxima 927 are very happy with the results in terms of wear (or the lack of) and it apparently burns very cleanly troo.

 

[robertjinnes]

good oil info

TDI, good reasoning on why the extra oil increases power.-- trade off increasing oil can hurt fuel burionging efficiency for a given amount of fuel but we can trade off extra oil and poorer efficiency if we are able to boost the cylinder pressure with better sealing.

Paraphrasing what you said.--- If we can't keep it spinning we aren't making horsepower.

OIL IT- OIL IT- OIL IT

 

[blsnelling]

Brad, if you like my 7901 will be coming apart soon and it's had a diet of 98RON fuel and Motul 8002T OR @ 40:1.
I'll post the pictures of the piston and chamber in this thread.

I'd love to see pics of it.

 

[computeruser]

This is one of the best threads that this site has seen in a while. Sooner or later I'll finish up my inventory of MobilRacing MX2T, so it's nice to see what others are pleased with.

 

[wigglesworth]

This is one of the best threads that this site has seen in a while. Sooner or later I'll finish up my inventory of MobilRacing MX2T, so it's nice to see what others are pleased with.

Im in the same boat as you, but im running out FAST!!! In fact, Ill be out by this fall. The motorcross buddy of mine is wanting me to try this....CASTOR 927

 

[computeruser]

Im in the same boat as you, but im running out FAST!!! In fact, Ill be out by this fall. The motorcross buddy of mine is wanting me to try this....CASTOR 927

Yeah, my inventory has really dropped since buying a Toro 2-stroke snowblower that I use for our house and three or four neighbors...all corner lots.