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.

 

[Don2222]

Here is my exact same model with a carburetor issue. It runs for a few seconds and then dies.

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This MS171 does not even run at all so I am a little baffled.

 

[salecker]

Have you tried to get it to run with some gas dribbled into the carb or spark plug hole?
Have you checked the condition of your piston?
"Things to try before tearing the carb apart" for $500 Alex

 

[JRHAWK9]

The Stihl chainsaws are the best.

.........and refers to an MS171.

 

[zrock]

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.

Does not take alot to plug it. Small carb/engine doe snot give it enough vacuum to pull a lot of fuel so if it starts to get plugged it has a hard time sucking fuel.

Yes they are a PIA to pull out i just used a hook pick and fished it out

 

[Don2222]

More info on the saw.
The store tech tested the compression and got only 80 PSI out of about 140. The cost of fixing it is about $330 more that the cost of a new MS172 which is about $230 :-(
Any suggestions?

STIHL MS 172 C-E 16 in. Light 01 Bar 31.8 cc Gas Chainsaw Tool Only Picco Micro Mini 3 PMM3 Mfr# 11482000213 - Ace Hardware

Crafted with an updated, modern design, the MS 172 C-E chainsaw is a powerful, lightweight tool equipped with STIHL Easy2Start technology so users can get to work with ease. The MS 172 C-E chainsaw comes equipped with a 16 inch Light 01 guide bar and a side-access chain tensioner which allows...

www.acehardware.com

 

[Whitenuckler]

More info on the saw.
The store tech tested the compression and got only 80 PSI out of about 140. The cost of fixing it is about $330 more that the cost of a new MS172 which is about $230 :-(
Any suggestions?

STIHL MS 172 C-E 16 in. Light 01 Bar 31.8 cc Gas Chainsaw Tool Only Picco Micro Mini 3 PMM3 Mfr# 11482000213 - Ace Hardware

Crafted with an updated, modern design, the MS 172 C-E chainsaw is a powerful, lightweight tool equipped with STIHL Easy2Start technology so users can get to work with ease. The MS 172 C-E chainsaw comes equipped with a 16 inch Light 01 guide bar and a side-access chain tensioner which allows...

www.acehardware.com

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I am not the expert, but I'm not sure how important that store measurement is. That should run I would think. It's not been running for a long time, so it's pretty dry in there.

 

[Geezer77]

More info on the saw.
The store tech tested the compression and got only 80 PSI out of about 140. The cost of fixing it is about $330 more that the cost of a new MS172 which is about $230 :-(
Any suggestions?

STIHL MS 172 C-E 16 in. Light 01 Bar 31.8 cc Gas Chainsaw Tool Only Picco Micro Mini 3 PMM3 Mfr# 11482000213 - Ace Hardware

Crafted with an updated, modern design, the MS 172 C-E chainsaw is a powerful, lightweight tool equipped with STIHL Easy2Start technology so users can get to work with ease. The MS 172 C-E chainsaw comes equipped with a 16 inch Light 01 guide bar and a side-access chain tensioner which allows...

www.acehardware.com

I think you just answered your own question.

 

[qwee]

Move on that saw is toast. No compression is a no go. Be grateful for its long service. And stop using Stihl Ultra. Use something like Echo Red Armour or Amsoil Saber instead.

 

[salecker]

Like i said a bunch of posts ago
Look at the piston...
That is one of the first things i do when i get a saw new to me that i have no history on, or for some reason doesn't start.
If the piston has damage there is no need to go further.
Then if there is damage before you take it apart do a vacuum and pressure test to find the cause of the piston damage(low compression)

 

[Whitenuckler]

Like i said a bunch of posts ago
Look at the piston...
That is one of the first things i do when i get a saw new to me that i have no history on, or for some reason doesn't start.
If the piston has damage there is no need to go further.
Then if there is damage before you take it apart do a vacuum and pressure test to find the cause of the piston damage(low compression)

I find it hard to believe the OP burned out the engine by putting it away. It still sounds like no gas into the engine.
Of course if the engine is blown, it could not pump gas into the carb.

 

[Don2222]

Hello
I always used MotoMix and the stove salesperson told me this model has not been around long enough to know how it stands up?
Anyway, here is a good video on the causes of low compression and how to check any scoring and the piston and rings.

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[qwee]

Don2222, what are you going to do now? Buy a new saw?

 

[Whitenuckler]

Don2222, what are you going to do now? Buy a new saw?

And will your old saw be parts for the new one or did they change everything?

 

[Don2222]

And will your old saw be parts for the new one or did they change everything?

I got the new Improved Model this year.
Yes I can use the old one for most of the parts.
The MS172 and it has the most engine primer bulb for starting the first time for the season.
MS172 first start

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MS172 Unboxing

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This review says it is still good - a Cracking replacement.

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[salecker]

I find it hard to believe the OP burned out the engine by putting it away. It still sounds like no gas into the engine.
Of course if the engine is blown, it could not pump gas into the carb.

I doubt it burned up putting it away
Using it without being tuned properly is one way to burn it out,dirty air filter, or a seal issue.
Vacuum and pressure testing will revile where the problem is.

 

[qwee]

I don't trust Stihl Ultra at a 50:1 ratio. And that is what is in Stihl Moto Mix. I would use better 2 stroke oil in the new saw. And I would do a 32:1 ratio or at least 40:1 ratio. Stihl Ultra appears to be minimally acceptable - anything off (dull chain, clogged, air leak) and it doesn't provide the extra protection better 2 cycle oils provide (especially at 50:1).

 

[salecker]

I use 32:1 mix for all my 2 stroke stuffs
Ported, stock, new, vintage all get 32:1

 

[John Mc]

I don't trust Stihl Ultra at a 50:1 ratio. And that is what is in Stihl Moto Mix. I would use better 2 stroke oil in the new saw. And I would do a 32:1 ratio or at least 40:1 ratio. Stihl Ultra appears to be minimally acceptable - anything off (dull chain, clogged, air leak) and it doesn't provide the extra protection better 2 cycle oils provide (especially at 50:1).

I don't trust Stihl Ultra at all. Too many pro users have reported problems with it.

The Husqvarna XP+ full synthetic is a good 2-cycle oil is a JASO FD rated oil. The Echo Red Armor that @qwee mentioned is also good (and also FD rated).

I run 50:1 in all my saws using Husqvarna XP oil for the past 10 -12 years years (since about a year after it first came out) without a problem. I've never found a need to to run a mixture other than what the saw manufacturers recommend, and have had good life out of all of my saws. It do run only ethanol-free gas in my small engines. I do also pay attention to how old my mix is. When it gets to old, it gets dumped in my antique truck, which will run on just about anything. The canned stuff is just too expensive for me to consider, especially since I'm getting good results without it. If I were only running small amounts and my saws tended to sit for a long time, I'd probably consider it.