Stihl MS 180-C Scored Piston... Tsk Tsk

[Sam R]

I bought a pair of MS 180's for carving, in no time one was running poorly and became hard to start. The shop took out the carboned up screen and I went home and removed the screen in the other saw as the Stihl shop told me it was a regular problem. Both the little saws have been good runners since the screens were removed.

Yeah, some people take those off - as a shop mechanic I'd probably be liable *if* someone started a fire with exhaust and it came out I took the screen out. That being said it's no big deal to replace or really, just torch them with a butane torch and clean them up when they get nasty.

 

[Sam R]

Okay, update on the 180-C... I ran a full diagnosis today, called the customer but didn't get an answer - did get some pics. A few things of note: the aforementioned caked w/ carbon arrester & muffler. The crankcase still seals.. although oddly the existing plug leaked a bit of air through the threads. New plug solved that. The big thing was that the LD (low mix, the only adjustment this carb has) was turned out 8 full turns. Wow! Maybe it was running a little rich? Finally, the cylinder *and* piston are both scored. Not awful, the saw still ran when I first got done fixing the choke/killswitch (multi-function) lever. But, well you can see the pics... It's not totally melted but this saw is about 18 months old.

 

[HarleyT]

Put up a pic of that carb, and the adj. screw.
It likely is the idle adj. screw.

 

[Sam R]

It's the low adjust, I am sure of it. Idle screws don't screw into the carburetor body.

 

[HarleyT]

idle adjust

 

[HarleyT]

here.

 

[HarleyT]

 

[Chainsaw Jim]

I don't see any scoring on the cylinder from what you showed pics of. The piston has a few scratches but nothing appears transferred to the cylinder.
It isn't uncommon for homeowner saws to come in with loose spark plugs, carb settings way off, and bad fuel.

 

[Fred Pulaski]

My brother got me started here so here goes. Have a Stihl chainsaw. MS 251 C BE-z. The serial # 296475468 Older version. It overheated and scored the piston. I figured I could save some money buying the cylinder and piston and repairing it. I was thinking of getting aftermarket parts. Any ideas?

 

[blsnelling]

Sounds like the only thing this saw needs is decarboned.

 

[stubnail67]

Sounds like the only thing this saw needs is decarbonated.

what's the best way to decarbon one?take it apart and clean it with scotch brite pad? then reassemble? i have some saws that are all carboned up on my shelf is why i ask.....older poulans.......

 

[stubnail67]

Let me re ask it .. i know how to clean the exhaust port... i mean if the top of the piston etc has heavy carbon build up also....is there a product you can drop the piston down and let it soak ?

 

[Sam R]

Weird! Never seen an idle screw like that. Makes sense though, I'm more intetested how this idle works since it's not the usual mechanical device.
The carb works good, the saw ran good except for a carbon fouled plug and blocked screen.

The pics aren't great, it's definitely got some scoring on it. It's not a killing amount, I could try and clean it up but I also have to follow Stihl guidelines with regards to repairs.
The only leak in the crankcase was the spark plug, a pretty easy fix.
The mystery now is the amount of carbon fouling on such a new saw. I wonder what the guy was using in it or perhaps if he commonly ran it at partial throttle...

 

[HarleyT]

The air filter gets dirty on the wrong side on these too.

 

[HarleyT]

Check the needle/height/etc. Also loose welch plugs.

 

[stubnail67]

I have a few guys i grew up with more then once they ask me to p-eek at their saw... it will be out of gas i say put your mix in..... they pour lawn mower gas in it then grab the lil bottle your supposed to use in a gallon or even motor oil add it to it and commence to shaking it up......I usually laugh and go lets pull your plug... 9 times out of ten its black ....and the screen will also be plugged.... he probably was a 16-1 sorta guy ......these guys are not dumb asses but they do it that and used motor oil for bar oil ....I tell them the speel and they ignore it and ruin the saw buy a new one every year or so .... or i get it and its either scored or full of carbon.... with a plugged oil pump ......I bet he added oil to the tank.......it shocks me how many people do this.....good for skeeters......

 

[Toyboy]

Would using outboard oil do that?