# Stihl ms 211 C Help needed please



## 1964johnr (May 21, 2019)

I have spent the last few weeks getting to know the insides of my chainsaw. It started running rough and then wouldn't start at all. I have managed to get it running a few times just for a minute or two before it conks out. I have done everything I can do without success so i'm hoping someone out there can offer advice. This is what I have tried so far.

Tried two fuel filters and two spark plugs.
The air filter is new and clean.
Set H L screws to factory settings.
pulled the fuel line to check it. It seems fine.
Removed the fuel tank air vent and cleaned it.
Removed the muffler and de-carbonised it. It's a one peice with no screen to remove.
Tried new fuel.
carb cleaner on the carb, in all holes.
put a new carb kit in.
There is no scoring on the piston skirt.
stripped it down to piston. smooth layer of carbon on piston crown which i cleaned off. Rings move freely.
put new baring seals in and put cylinder back together with new high temp, fuel resistant gasket sealer.
The top of the cylinder inside is pitted all over in a uniform pattern as if something hard got between the top of the piston and the cylinder crown and bashed it about. /i cleaned the carbon deposits from the pitted cylinder crown.
I put it back together today and put the chain on. I got it running for a few minutes, tipped the saw upside down and side to side, no change in engine sounds. There seems to be a loud continuous knocking sound from the engine.

Now I do know that It should have had a compression test and a leakdown test , but that costs money and spending out was what I was trying to avoid. So far I have spent £20 sterling so no big deal.

One more clue, when I put it back together and fired it up I took the chain break off and turned the idling screw in to increase the revs to start the chain moving, but I turned it all the way in and the chain did not move. 
Does anyone have any ideas?


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## paulr44 (Oct 14, 2008)

Running rough when? Idle? Full throttle? Rough how, missing/stumbling, or surging?

If you can turn the idle speed screw in fully without any change, most likely it's running too rich (too much fuel). I'd be surprised it'd idle at all before...you're describing more than one condition. YOU MAY want to check for a collapsed carburetor metering diaphragm, which would allow too much fuel to be administered. Pressure testing the carburetor (via fuel inlet fitting) is one method, else physical inspection.

As for the knocking, did that occur before or after you dismantled it?

How old is the FUEL MIX you're running? What octane is the fuel? BOTH very important.

FYI Crankcase pressure test shows bad gaskets/sealant, while vacuum test shows bad seals. Leak down test is for 4-strokes. However, a 2-stroke of that size should have no less than 120-130 psi compression.

BTW, how old is this saw and how much use have you put it through? It's not an expensive saw...


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## finaprint (Jan 29, 2006)

May have pieces of a needle bearing going through it. The knocking and dents in head. Maybe piston hitting head from dead bearing again.


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## 1964johnr (May 21, 2019)

if I am able to start it, it will only run if I give it a little throttle. If I take my finger off the throttle it conks out. It doesn't sound like it's missing, and it's not racing. It does sometimes sound like it's bogged down.I put a new carb kit in, so it has a new metering diaphragm. I will check it again, but it seemed to go on fine when I did the carb kit. It also gives out a lot of white smoke if I get it running. When I pull the spark plug, it is always wet and covered in oil.

I'm wondering if the metering needle is set correctly with the spring. I don't have a tool to set it so watched a you tube video by donnyboy73 and set it in line with the top of the carb. It's an 8 year old saw which is used to cut wood for our open fire and therefore gets moderate use. I mixed a new fuel load at 45 - 1 mix ratio. Not sure what the octane it is, it came from a local supermarket. One thing I did notice when I put the new carb kit in was that the small screen in the carb was varnicised and looked partially blocked. It has a new one in it now. If it's running rich and the metering diaphragm is working, how could I reduce the fuel to air ratio ? The knocking sound was only noticed after I stripped it down and put it back together.


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## finaprint (Jan 29, 2006)

Yes, but if assembled wrong to knock then likely something is going to tear up. Wasted time tuning something like that.


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## Milton Fox Racing (May 27, 2014)

Or something has/was already broke.

After 8 years it maybe hard to tell anymore, but is the whole thing vibrating (in one direction or the other) when it does run? More than normal of course. :cheers2:


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## 1964johnr (May 21, 2019)

Yes, I have noticed that when it does run it vibrates much more than normal. Maybe that is caused by incorrect functioning of the piston which may be something I did incorectly when putting it back together, or perhaps the pitting on the crown of the cylinder is interfering with correct running.


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## finaprint (Jan 29, 2006)

If say you put piston in backwards you have likely broken rings, as they are indexed into the piston to keep the gaps out of port windows. The rings break instantly if the ends pop out into the port.


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