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

Back in my lawn care maintenance business days we'd periodically remove and soak the mufflers in a can of strong parts cleaner and it would break down and dissolve that buildup, no problem.
 
The design of the muffler also affects this. Some mufflers run hot enough to burn the stuff off during normal operation, and some don't.
 
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.
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Interestingly enough, I also have an SRM-225 and it has all kinds of goo that is around the muffler. I have only ever run Echo oil in it, first some PowerBlend Gold (mixed 50:1) and since then some RedArmor, a little between 40:1 and 50:1. I dont think there is carb adjustment I can make, and it definitely runs a little on the fat side, I assume tuned that way for emissions. Would love to see what I can do to make it not as messy, but it still starts right up and runs great, so cant complain.
 
Chris142 said:
42:1 don't the units call for 50:1?
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I know you werent responding to my comment, but here is my .02

The 3oz is pretty easy to measure out, and doesnt usually hurt to run a little richer, especially if you share the same gas can with some older equipment that was previously run on 32:1.
 
3oz per 1 gallon is what I use now for safety. I fill my can to 0.990 ~ 1.000 gallons on the pump and if you think getting the pump on the round dollar is hard, try getting it on the round "gallon" without accidentally going over. But anyways to my point depending on what pump and at what station you get the fuel, I am either 1/4" above / dead on / or above the one gallon line on the can. Some pumps will dispense the whole hose before the solenoid picks, and some don't. Some have the seal of approvel from weight and measurments department and some have failed.

My real point is using this same gas / oil mix in certain units have ZERO tar, others do.
 
With linetrimmers the main causes of slobbering are using a nylon that is too thick for the machine and removing the gaurd and having the line out too far.Both these actions cause the motor to run slower than it should.Remember most small engines are jetted for full throttle and idle only.If you operate at lower speeds the engine runs richer and cooler,hence the carbon build up.
Can Warlord explain how the 'cheap' Stihl 2 stroke is in any way unsuitable for use in most 2 stroke engines.I have sold thousands of litres of Stihl HP over 30 years and have not any lubrication problems with any machines of any brand.
 
Jimmy great point indeed, I never run without a guard, and I run the recommended 0.095" line even though the 0.105" will physically fit in the spool. I also make certain to dispense the line and let the cutter blade whack it off fresh before making a carb adjustment / tune. It made no difference for me. Over time still black goo,.
 
There are quite a few factors:
1. How the engine is designed can impact how clean it burns
2. Fuel quality
3. Fuel/oil mixture
4. How rich the engine is running
5. If it is running for long enough at full throttle to burn up the carbon in the exhaust
6. The 2-stroke oil that is being used, some produce more soot than others
 
I have an Echo 225 running at 50:1 and I rarely run at full throttle, no problems with splooge or carbon or anything. Same with my Echo chainsaw, but I really dont use that very often, probably not enough to have a problem. I have been using mostly Stihl oil recently, as I bought a fairly large bottle of it last year and am still going through it. But I have used various other brands (Pennzoil, Echo, Walmart whatever) and havent had these kinds of issues.
 
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...
Just keep your exhaust ports clear, and burn the crap off your spark arrester. Anything else is a non starter.
 
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