I have a Stihl MS170 that was gifted to me a few years ago when my parents were downsizing. It worked reasonably well for a while, but I just can't get it to start. I've replaced the carburetor, fuel line, fuel filter, air filter, and spark plug. I'm pretty sure I'm getting a spark. Checked the arrestor and it's clean. After multiple pulls with choke on and off, I get nothing. What else could it be?
Stihl MS170 Won't Start
- Thread starter plassey
- Start date
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Well, step one is don't be pretty sure it's getting spark... be sure. When you pull the plug to check spark, you can confirm fuel at the same time.
Yes, it is definitely getting spark, and when I pull, I see fuel in there. The fuel is brand new - ethanol free mix. Any thoughts?
The flywheel key should be checked, see if it's sheared also pull the muffler and look for a scored piston, also is the plug fouled?
Thanks - the plug is brand new and clean and gets a consistent spark. I checked the piston looking at it behind the muffler and it looks shiny and clean. I'm not sure how to check the flywheel key (and I don't even know what that is), as the plastic casing is difficult to remove. Any tips there? Otherwise, what else could be preventing this thing from starting? I've worked on my Stihl weedwacker (replacing carb, fuel line, filters, plug, etc.) and have had great success. For some reason, this machine does not like me. Am I missing something simple?
You have to take the flywheel off and look at the key to see if it is sheered.
If your replacement carb is an inexpensive Chinese model I'd inspect the metering side closely.
Not another Chinese carburetor! That will add to the 4 I replaced to make a saw run this month.
Inspect it for what? I'm a novice with small engines
Is it an aftermarket carb or STIHL carb?
jcquade
ArboristSite Member
it may be something as simple as being flooded. I would pull a spark plug and spray it out well with the air compressor and then let it sit a day.
It's definitely an aftermarket amazon carb. You get what you pay for?
Well, that right there certainly could be the problem. Now, if the saw isn't flooded and the plug has fire when testing, you should be able to put a small amount of fuel in the plug hole and get the saw to at least run for a second. If it does, buy a new OEM carb if not check the flywheel key .
There are several good in depth YouTube videos covering 2 stroke carbs. After watching and learning you'll know. I've seen new carbs with damaged diaphragms, ones missing metering spring, and or needle. Incorrect lever height. Get busy!!
hacskaroly
ArboristSite Member
No need to go through that for a flooded saw, just drop it down to fast idle and give it about 25-30 pulls, it should clear anything out and start running (may smoke for a short bit). This way you can get right to work!
jcquade
ArboristSite Member
curious did you get it running
Geeze, these are $100 saws, used… $199, brand new…
I have two to get rid of for a friend…
I have two to get rid of for a friend…
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