Spark arrestor issus

[John O'Brien]

Ok, I am hoping that someone else out there has some insight on this:
I run a wildland fire crew and use the MS 460 chainsaws for both project and fire work. With the ethonol issues we decided to run Startron enzyme gas treatment, along with the Sthil fully-synthetic mix oil. 50:1 mix ratio also adding octane boost to the mid grade gasoline (only blend we can buy here at work, long story so dont ask) I image the octane is around 87 with boost maybe 95............

So what we are finding is that the fuel is not boiling like it did last season so thats good. But now we have 2 saws with ongoing spark arrestor clogging issues. The entire inside of the muffler has a gummy residue, and the spark arrestor is a solid mass of carbon. On one of the saws, we replaced, the spark plug, changed carbs, and put new air / fuel filters in it. None of this seems to have helped.

These saws are some of the older ones we have, does anyone think that low compression might be causing the issue? We are waiting for the comression tester to arrive, so have no idea what the numbers are but they appear to still have decent compression on the pull rope.

So far, no one including our Sthil representative, have come up with a difinitive answer to whats going on. I have never seen a saw nearing the end of its life clog spark arrestors, but that was back in the pre-ethonol days. Anyone out there have any ideas?????????????

 

[mattfr12]

we run 97 octane in them and still end up having to tear the muffler apart from time to time we just burn all the stuff out with a propane torch some of them have that screen in thier that will completely block off then they run like crap.

if its happening a lot it would probably either be the fuel or the additive enless you have a terrible tune wich im sure you would know by just running it. i dont add anything to my fuel other than the mix i think stihl says to run 97 octane in thier manual. not 100% sure tho.

i would guess the additive might have a hard time burning it off complety blowing it into the exhaust system.

ask your stihl guy if you can try running a leaner mixture like 40:1 might help it stay cleaner run a little hotter to keep the junk out.

 

[superjunior]

i dont add anything to my fuel other than the mix i think stihl says to run 97 octane in thier manual. not 100% sure tho.

I gotta look at a manual for one of my newer stihls, I thought the guys at my stihl dealer told me to run reg 87 and stihl mix

 

[Grouchy old man]

i think stihl says to run 97 octane in thier manual. not 100% sure tho.

I thought the guys at my stihl dealer told me to run reg 87 and stihl mix

Stihl as well as all 2 stroke manufacturers that I know of say to use at least mid grade- 89. Never 87 or lower.

 

[Scrat]

John,
I am not well informed about the Startron but it is a natrually occuring enzyme. A number of years back I had been running yamalube 2 cycle oil in our race skis and was happy with the performance so we decided to run it in our KDX dirt bikes. Well it was bad since it was a natural castor based oil and although great in the skis it quickly gummed up the kips valves and left a gooey residue in the exhaust silencers/spark arrestors. I know the product says just the opposite but the exhaust screen holes may be too small to let the product pass. other possibility is the product works as described and the older 460 mags had alot of hard carbon build up that the enzyme is breaking down and plugging the screen on the way out.
Best of luck
Scrat