strange problem on Stihl ms170 chainsaw


Old 04-19-09, 06:48 PM
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Join Date: Apr 2009
Posts: 3
Question strange problem on Stihl ms170 chainsaw

This saw was working just great .. and has maybe 30 hours on it over 4 years. Problem is now .. it floods when I start it normally.

Usually I put it on choke (cold start) then crank once or twice till it sputters .. flip it to 1/2 chok, pull it again and it runs .. then flip to no choke after it settles in .

Now, it sputters on choke but when I pull it again on 1/2 choke it floods right away .. and there is no hope to get it going without taking out the plug and drying off the gas. I also tried bypassing the 1/2 choke stage but that does not work .. either .... the only way to get it to go is to get a sputter on choke .. then a few pulls on 1/2 choke then take the plug out and dry it/replace .. then start it without any choke at all ... then it runs normally ??

Any ideas ?? Peter[/FONT]
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Old 04-19-09, 07:06 PM
Join Date: May 2006
Location: Iowa!!!!!
Posts: 3,728
The first choice would be the needle/seat on the diaphragm leaking. Most would just put a kit in the carburetor. You might buy a little relief by adjusting the low idle screw if it isn't capped off, but it would likely be short term.
Old 04-21-09, 07:02 AM
Thread Starter
Join Date: Apr 2009
Posts: 3
OK .. Interesting, I went to the dealer and bought a new Kit and I'll do that soon and report back on success .. 99% sure that'll fix things.

The guy in the shop said that the diaphragms are good for 3-4 years now because of the alcohol in gas .. he said I should use higher octane gas 'cause it has less alcohol.

Old 05-06-09, 06:24 AM
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Join Date: Apr 2009
Posts: 3
Problem Solved

When i took it apart, I found bits of hard material .. like varnish. I'm pretty sure that one very small piece was lodged in the valve seat. I replaced all the parts anyway from the kit and it worked great.

But the bits of varnish are still a mystery. They kind of look like a glue that was put around those sealer caps ( or whatever they are called) but maybe that varnish just forms over time .. or over winter... maybe it forms in extreme cold.

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