Stihl MS171 chainsaw will not start this season?

[Don2222]

Hello
The Stihl chainsaws are the best. However this MS171 just refuses to start after sitting in the garage all winter with maybe a little MotoMix gas from the old can left in the tank. The store told me that the MotoMix should not gum up and cause a problem. However I switched to the new can and it still did not start.
So here is what else I tried.
1. - In case it was flooded, I Tried to start on the hi setting with choke partially open.
2. Replaced the spark plug with the OEM NGK plug. CMR6H NGK Spark Plug
3. Pulled spark plug and dimmed lights and checked for spark when pulling the rope to start. Therefore Ignition looks good.
4. Checked and cleaned the air filter. Tried starting without the air filter with no luck.
5. Checked the linkage to assure the choke was fully closed when starting cold but unlike the MS170 the linkage was greatly improved so it does. It easily get bent causing the choke not to fully close. Also checked carburetor butterfly to assure correct position for each setting when starting cold, warm and running.
6. Checked the spark arrester screen but unlike the MS170 it also has been redesigned and comes apart with a Torx driver instead of 8 mm socket but made smaller up top so it does not clog easily. Even so, I blew it out with a compressor. Also blew out all the sawdust.
Any other ideas like changing out the carburetor? Are the aftermarket carbs that are way cheaper as good as the OEM carburetor?
Pic 1 & 2 - Old MotoMix fuel can
Pic 3 & 4 - New MotoMix fuel can
Pic 5 & 6 Stihl MS171
Pic 7 - Fuel filter
Pic 8 - New OEM spark plug
Pic 9 - Carburator air intake closed
Pic 10 - CMR6H NGK Spark Plug

 

[aerocolors]

Have you checked the fuel line in the tank for cracks? I have had this cause starting issues

 

[Whitenuckler]

Hello
The Stihl chainsaws are the best. However this MS171 just refuses to start after sitting in the garage all winter with maybe a little MotoMix gas from the old can left in the tank. The store told me that the MotoMix should not gum up and cause a problem. However I switched to the new can and it still did not start.
So here is what else I tried.
1. - In case it was flooded, I Tried to start on the hi setting with choke partially open.
2. Replaced the spark plug with the OEM NGK plug. CMR6H NGK Spark Plug
3. Pulled spark plug and dimmed lights and checked for spark when pulling the rope to start. Therefore Ignition looks good.
4. Checked and cleaned the air filter. Tried starting without the air filter with no luck.
5. Checked the linkage to assure the choke was fully closed when starting cold but unlike the MS170 the linkage was greatly improved so it does. It easily get bent causing the choke not to fully close. Also checked carburetor butterfly to assure correct position for each setting when starting cold, warm and running.
6. Checked the spark arrester screen but unlike the MS170 it also has been redesigned and comes apart with a Torx driver instead of 8 mm socket but made smaller up top so it does not clog easily. Even so, I blew it out with a compressor. Also blew out all the sawdust.
Any other ideas like changing out the carburetor? Are the aftermarket carbs that are way cheaper as good as the OEM carburetor?
Pic 1 & 2 - Old MotoMix fuel can
Pic 3 & 4 - New MotoMix fuel can
Pic 5 & 6 Stihl MS171
Pic 7 - Fuel filter
Pic 8 - New OEM spark plug
Pic 9 - Carburator air intake closed
Pic 10 - CMR6H NGK Spark Plug

Sounds like a carb issue. I would take the carb off and take it apart and clean. Also verify your line to the crankcase. If it it were really old and well used you you need to check the crank seals and compression however I guess it just won't start. I have been watching some good utube video's on 2 stroke carbs and engines. There is more to it than it appears. The crank pressure pumps the fuel into carb and there is a one way valve made by a flap in the carb pump. There is a needle too that could be stuck before the main jet.

 

[Murray01]

Back in the day I had a 4 stroke dirt bike that wouldn’t start after winter, was told to put a tablespoon of oil in the spark plug hole and kick it over a few times without the spark plug. Rings had dried out and I didn’t have enough compression to start. Worked every spring. Don’t know if that applies to 2 strokes.

 

[zrock]

Have you pulled the fuel filter out of the tank and changed? I found mine was full if fine sawdust a few years back and they are a real PIA to get out and change. These are great little saws i have one sitting in my shop dead since the dealer sold me the wrong chain to go with the bar so the thing would never cut properly no matter how i sharpened the chain and i have always been able to sharpen the chain to the point it would be to aggressive for the little saw. Did not figure out the bar and chain issue until it was to late and i hurt the motor.

 

[Don2222]

Have you pulled the fuel filter out of the tank and changed? I found mine was full if fine sawdust a few years back and they are a real PIA to get out and change. These are great little saws i have one sitting in my shop dead since the dealer sold me the wrong chain to go with the bar so the thing would never cut properly no matter how i sharpened the chain and i have always been able to sharpen the chain to the point it would be to aggressive for the little saw. Did not figure out the bar and chain issue until it was to late and i hurt the motor,

Thanks. Good suggestion. How does the fuel filter come out. Does it just pull out where the gas cap goes on?

 

[Whitenuckler]

Thanks. Good suggestion. How does the fuel filter come out. Does it just pull out where the gas cap goes on?

Yes you need to drain the tank good. Maybe take the bar and chain off too until you get it running. Then if you shake it you will here it inside the gas tank. Then you get a piece if DULL stiff wire and snag it out. The pro's have a tool. You could then inspect it. It would have to be pretty dirty to totally fail.