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Hey everyone,

I've got a problem with my little MS180 that I can't figure out. When running, it spits a nasty, oily black mess out of the muffler. It's clearly coming through the combustion chamber since it's so black, but why is this happening? I can only surmise that it's running way too rich. However, with no mixture screws, how is this happening?

Notes: the saw might have 5 hours of run-time; it's one of my homeowner saws for working on my property only, and I've used it maybe 3 or 4 times for light limb cutup.
Spark Arrestor was pulled out when it was new.
It only gets 89-octane ethanol-free fuel with Stihl 2-cycle oil.
The spark plug looks oily and messy (just like a rich-running plug should look).
Air Filter is clean.
New fuel or fuel that's been in the tank for a bit sees no change in the oily mess from the muffler.
Piston and cylinder walls look like they're new (they basically are).
Fuel filter has the same 5 hours on it.

Is this normal? Should I look for a new carburetor? I'm sure Stihl is only going to sell the non-tunable versions, so I'm thinking a Walbro WT-215.

Photos of my "issue" are shown below, but AFTER I started cleaning the mess off the saw. You can see the oily mess in the carb area in photo #1. Photos #2 #3 and #4 show the last of the black mess around the muffler area. Photos #5 and #6 show the back of the cylinder wall and the front of the piston - they're like new...

Thoughts, input, suggestions? Thank you!

Excessive oil coming out of the muffler indicates to me you are using the wrong fuel/oil ratio. Way too much oil. Stihl uses a 50/1 ratio, I use and recommend one pouch of Opti-2 oil to one gallon of fuel. Remove all fuel from the tank, mix a gallon of fuel to the proper ratio, install a new plug and start over. It’s going to take a while to burn off the oil in the muffler, so is going to smoke until you have everything cleared up.

Rivets said:

Excessive oil coming out of the muffler indicates to me you are using the wrong fuel/oil ratio. Way too much oil. Stihl uses a 50/1 ratio, I use and recommend one pouch of Opti-2 oil to one gallon of fuel. Remove all fuel from the tank, mix a gallon of fuel to the proper ratio, install a new plug and start over. It’s going to take a while to burn off the oil in the muffler, so is going to smoke until you have everything cleared up.

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I'm using Stihl brand 50:1 ratio oil with non-ethanol fuel. I am no stranger to Stihl 2-strokes and have had dozens of them, work on all of my own equipment, even rehab old and damaged Stihl equipment as a sideline.

This is something different. I'm OCD with my fuel/oil mix cans: I only use 1-gallon fuel cans and the Stihl oil bottles made for 1 gallon. One bottle for one gallon of gas - that never changes...

Any other ideas?

Sorry everyone - forgot to attach the photos, but they're in the post now

I’m then at a loss. The only place where oil can enter the cylinder is with the fuel.

That should be a Zama C1Q-S57A or the current Stihl replacement.

Rivets said:

I’m then at a loss. The only place where oil can enter the cylinder is with the fuel.

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I'm with you! This one has me puzzled. I've read of folks changing the mixture settings via internal adjustments to the carburetor, but that is outside of my wheelhouse - I can rebuild the carburetor, but I don't like tinkering with all those little parts to begin with. Making changes to them is not going to happen.

I'm really thinking the carb is at issue, but I can't say why I think that way. There is something just wrong about putting a non-adjustable carburetor on a carbureted motor, so I'm likely going to wait a few days for replies to this thread and see what folks come up with.

StarTech said:

That should be a Zama C1Q-S57A or the current Stihl replacement.

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It is a ZAMA on it from Stihl: C1Q-S152E - came that way from the dealer less than 2 years ago

5th picture looks like scoring of the piston. What does the cylinder wall look like through the spark plug hole.

ILENGINE said:

5th picture looks like scoring of the piston. What does the cylinder wall look like through the spark plug hole.

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There's no scoring of the piston or cylinder walls. I've looked at it through the intake side, the exhaust side and through the plug hole - my camera picks up every single minute detail in an object photographed.

I know scoring can happen fast, and I've repaired saws that have severe scoring. This motor has 5 hours on it if even that. It's been used only a few times, but each time (THIS INCLUDES THE FIRST TIME I USED IT), it dribbles oil out the muffler, even spits it out in some cases.. :-(

UPDATE to the issue with this MS-180:

Success! This saw runs flawlessly now, and there's no more spitting oil and fuel everywhere.

What I did: ordered a Walbro WT-215 carburetor, made the modifications to the air box and the housing to gain access to the H, L, and LA screws. I also added a paper gasket between the metal portion of the air box and the intake side of the carburetor - don't know if that did much, but there was so much oil/fuel in that area that I thought it couldn't hurt.

There are some videos on the web showing that you need to bend the throttle linkage in several different places, but I found that just bending the forward "hook" of the linkage forward about 1/8" worked perfectly to reach WOT.

Also, since that strange little black filler panel MIGHT have gotten in the way of WOT, I cut out the area just forward of the throttle linkage movement as it approaches WOT - did this with a Dremel. I didn't look for any clearance issues during fitment, but this was an easy modification, so it was done too.

Last modification was to free the exhaust flow a bit. I didn't go crazy, opting to open the vents up a bit with a large flat-blade screwdriver, and then I drilled those same vents with 3/16" drill bit one hole in each vent for a total of four holes and also removed the spark arrestor. Did the muffler mod make a difference? I don't know.

The final step was to tune the saw. Normally I do this with a digital tachometer, but I tuned this one by ear, backing WOT off a fraction of a turn until it 4-stroked a bit, then tested it "in the wood". I had to back the screw out maybe 1/16 of a turn to get the smooth WOT running in the wood and a slight bit of 4-stroking when pressure was taken off the chain.

SAW RUNS BETTER THAN IT DID WHEN NEW! I highly recommend the carburetor change to anyone having issues tuning (or other problems) with a 170, 180, MS-170, or MS-180.

PS: The "Stihl" (Zama) carburetor that came with the saw is marked "China" - discovered that when I could see all sides of the carburetor. Stihl is just not what it used to be, and I was VERY disappointed to see Chinese crap on a Stihl product. Glad most all of my Stihl equipment is 10-30 years old!