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
For a flooded engine you should have the choke completely open and pull it with the throttle wide open. You need all the air being pulled in to dry it out enough to start. Was the plug wet when you pulled it out indicating it was flooded? There are a couple other possibilities that come to mind. One is the coil has weak spark under compression despite you seeing spark outside the engine. It happens. There is also a possibility you have fines in your carburetor that have made it through the fuel filter and clogged the screen inside. I've see this more times than I can count on all brands of saws at one time or another.
Thanks for the tips. Is it possible to blow the carb out with a compressor to clear the fines? This still has the exact same starting lever as the one in this short vid https://m.youtube.com/shorts/QRMHskUbjEk Also for the MS171 and MS291 which differs than the MS170 and MS290, do you think that it is a good idea like it shows in this video below that when the chainsaw is cold to only give one starting pull in the full choke position then move it to the partial choke for the additional starting pulls? Here is another method of pulling with lever in full choke mode till it burps, then switch to partial choke. See vid below
As far as starting method...with every saw, weed eater, blower ect., when cold, I pull with choke on until it pops. Then choke of and pull until its running. After a very short period I stab the throttle to release the throttle lock so it can be at idle.
Here is my exact same model with a carburetor issue. It runs for a few seconds and then dies. My MS171 does not even run at all so I am a little baffled.
Try to start per normal procedure. Give it 10-15 good pulls. Pull the spark plug and see if it is wet and/or smells of fuel.
How I start a stihl saw: - If I remember, do a couple dry pulls with the lever set to off. seems to clear out the cobwebs - As in the video, lever all the way down, pull till burble sound - Move up 1 notch, pull, start - Let run for 5-10 seconds and then blip throttle to take last bit of choke off As soon as it doesn't start you don't even bother to try again. Pull the plug and clean it and yank the cord a bunch to de-flood it out the plug hole. There is a reason your scrench has a spark plug socket on it.
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
So the position is scored? Pull the exhaust and look at it yourself. Buying another pos 172 doesn't sound like a great idea if it's just gonna blow with the special gas and everything. Might be time for something electric
Do you have an echo dealer or home depot near by? I've owned the MS170 and the echo CS310. Hands down I prefer the 310 over the 170. Id definitely pull the muffler on the saw you have to look for damage.
I’d agree with this. I went several years ago to buy a small Stihl. The dealer took time to show me both, and talked about the differences, notably the air filter. I bought the Echo 310.
Plus adjustable carburetor, spring av and side chain adjustment. 5 year warranty too. They might have an adjustable oiler as well. Don't remember. my nephew has my 310.
Anyway, here is a good video on the causes of low compression and how to check any scoring and the piston and rings.
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 engine primer bulb for starting the first time for the season. MS172 first start MS172 Unboxing This review says it is still good - a Cracking replacement.
Donn. I had the same frustration with a MS 170 I had bought 2nd hand. My solution was I traded it in for a 192T.
