What causes certain 2-stroke engines to make black tar.

F

Fordiesel69

Joined
Sep 10, 2005
Messages
1,866
Location
Erie, PA
See photo:

A lawn care youtuber had issues with his fleet of echo SRM-225's producing black tar that would drip all out the muffler and into his trailer. He eventually complained enough his dealer upgraded his to SRM-230 models that did not have this issue. I recently aquired a husky 223L and still own my 323R and they both seem to make this black tar. However my blowers using the same exact gas do not produce even a whisp of this. It is basically a black sticky oil that melts when hot and turns rock hard when cold. It seeps out the muffler seams.
30ffbeeb-76eb-4dd2-a127-3c573b3cc946.jpg
 
All 3 of my two stroke machines do this. Never understood why.

Doesn't matter if I use E10, E5, E0, Synthetic or mineral oils etc.
 
The first possible reasons that come to mind are (A) oil mixture having too much oil, or (B) engine running rich, or (C) wrong spark plug heat range.
Can you use synth oil in a 2-stroke? Back when Mazda was making the 13B Wankel engines, they had oil injection at high throttle / RPM settings. Mazda recommended against using synth oil, saying it didn't burn as well as mineral oil. Also, mineral oils can hold more contaminants/particles in suspension than synth, which can be useful for dirty engines.
 
Called spooge. Irritating but mostly harmless unless it clogs up those exhaust screens which should be removed anyway. Your blower doesn’t make spooge cause it runs wide open and burns everything off completely. Trimmers run at various rpm and can start to leak the buildup. Some say run your trimmers wide open but I feather my throttles (I use a 223l and srm225 daily) and never get any spooge using decent oil. Switching to a JASO FD certified oil may well solve this. Some oils make a mess no matter what like the cheap Stihl oil.
 
I used to have trouble with a few of my machines no matter how the carburetor was adjusted. Since I changed over to Husqvarna XP+ oil, it has mitigated the spooge out of the mufflers.
 
Freischneider said:
I used to have trouble with a few of my machines no matter how the carburetor was adjusted. Since I changed over to Husqvarna XP+ oil, it has mitigated the spooge out of the mufflers.
Click to expand...
And the main culprits were these Husky and Echo machines with a catalytic converter muffler.
 
I havent seen more than minimal (spooge!?) with echo red armor oil. or VP racing both are jaso FD
 
Fordiesel69 said:
See photo:

A lawn care youtuber had issues with his fleet of echo SRM-225's producing black tar that would drip all out the muffler and into his trailer. He eventually complained enough his dealer upgraded his to SRM-230 models that did not have this issue. I recently aquired a husky 223L and still own my 323R and they both seem to make this black tar. However my blowers using the same exact gas do not produce even a whisp of this. It is basically a black sticky oil that melts when hot and turns rock hard when cold. It seeps out the muffler seams.View attachment 111115
Click to expand...
Thats how premix 2 strokes work. it's the oxidized dirty unburned oil thats been through the combustion process.

Some two strokes simply combust better than others based on piston, head. porting, pipe design and really only run efficiently in a narrow RPM band and once out of it - youre' pumping unburned oil.

You have to have enough oil in the mix to maintain MOFT at wide open throttle and load, and when running slower than that you are over oiled.

Any old motocrosser will attest to this. Leaner mixtures and better oil help.

an injected 2 stroke works a lot better, but no one wants to carry the weight of that in a saw/ hand tool.
 
Last edited:
Same oil/gas mix and the echo blower produces much less "spooge" than the echo trimmer.
My Redmax 8500 produces none on the same mix.
 
It is hard to get a complete burn at idle. The more time spent idling the worse this will be. There being no black stuff on the spark arrester screen means that it isn't running much too rich.
 
Do you run your trimmer mostly at partial throttle, or do you run it at full throttle? These are made to be run full throttle or you start getting results like this, blocked exhaust ports, or clogged screens.

L8R,
Matt
 
My experience is that the catalyst equipped two strokes don't have exhaust spooge. But I only have a modest collection of yard tools.
 
Ran my srm225 for about 3 hours yesterday mostly low throttle using Poulan synthetic. Dry, clean exhaust. Maybe experiment with different oils.
 
You must log in or register to reply here.
Back
Top