ms170 won't start back up

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qbilder

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I have been using an ms170 for general shaping on small burl blocks. It usually runs great and does a fine job, but yesterday started bogging intermittently. It would bog down like it was running out of fuel, then take off & run great again for a while before bogging again. Today it bogged, died, and won't start again. It fires when choked but won't fire in the run position. Spark is good. Seems like it's a fuel delivery issue. Figured i'd run it by yall & maybe get some ideas of things to look for when I tear it apart in the morning. Thanks much
 
I have seen the fuel hose crack on a couple of those little beasts, between the fuel tank and the carby so the they suck in air instead of fuel. They also dont like the tiniest speck of dirt inside the carby. Get your tweezers out and a watchmakers toolkit and be prepared to use a lot of swear words while working on the tiny little thing. They are one of my most hated saws to work on. Been thinking about putting a bottle of Valium in my toolbox so i can take one before attempting to fix another one of those.
 
Well I guess I'll find out today....if I can keep from tossing the bugger into the dumpster. Everything is so tiny & my fingers not so much.
 
If in doubt with the carb, order a Chinese copy off eBay. With these saws i often replace the carb rather than fitting a carb kit, as they're so fiddly with small passages and the cost difference is negligible
 
Mine started doing the same thing except it would start but only idle with revs high and bog down under load or just stop. It was a split fuel line and I put carby kit on & now starts super easy and will idle perfect.
Matt

Sent from my SM-J110F using Tapatalk
 
Just general MS170 info:

I'm working on two MS170's with fuel issues! One is bogging, other one would not idle until several CW turns of the idle adjustment.

Carb is easy to remove! 8mm socket and a torx to remove plastic cover on handle for throttle linkage access then remove kill wire and the plastic choke shaft and you are there.! OEM Zama carb C1Q 057A is bogging.

Ordered a Zama carb replacement yesterday from STIHL DEALER. 1130 120 0603@ $28 and a fuel hose 1130 358 7701@ $5.99. I can see damp gas on the outside of the old fuel hose.

See cheaper parts on flea bay but, Cannot bring myself to trust ebay for parts when it says from China.
I have purchased the real cheap ebay China chainsaw carbs just as a test carb to see if a expensive OEM Stihl chainsaw carb is the problem and if Chainsaw responds ok I go to work on the OEM carb, usually run it thru a ultrasonic leaner and then kit if replacement carb is costly. If carb happens to be one of the harder ones to remove and install I'll go for replacement rather than taking chance of having to kit, re-install, test and possibly remove again. (time repairing vs cost of complete carb replacement)

I don't leave a cheap China $10 carb on a high priced good saw.

There is a small hole thru the side of the black handle to adjust the idle speed with a very small screwdriver on these two MS170's. The idle adjustment is kinda slow to respond. Several turns of the screwdriver to get a throttle response. No H and L adjustments.

You need to look at the spark arrestor screen. (remove the 8mm nuts on the front of the muffler and it's right behind the little front plate) These two saws screens were clean but I've heard rumors of the 170 screen clogging mainly due to mixing too much oil in the gas. Saw will start bogging after it gets warmed up similar to carb/fuel issues.

Here is a link for the MS170 owners manual with some good info! The idle adjust says it Left hand thread, but the idle adjust instructions indicate it's RH thread??? (pg 41)

https://www.stihlusa.com/WebContent...TIHL-MS-170-180-Owners-Instruction-Manual.pdf
 
No need to take apart the handle to remove the throttle shaft. Just squeeze the trigger to open the throttle plate open,
and then while holding the throttle open with a finger or tool, release the trigger, and lift the rod out of the slot, and set it aside the carb. then it is lust a matter of lifting the rod, and tilting it back, and then remove the rod.
 
I would definitely start by looking for a fuel collapsing or filter plugged, mostly because it's easy to open the tank, and if for some reason you do think it's a carb issue, I highly recommend replacing the whole unit with factory they are not that high, good luck
ADLM
 
And I have fat sausage fingers and I have no problem working on them, just use your brain and some good tools rather than just muscles to do the job haha
 
Thanks HarleyT for that tip about disconnecting the throttle linkage at the carb slot W/O removing the two torx screws for access to the throttle trigger linkage and possibility of spring flying out.
I noticed the slot in the carb shaft for the throttle linkage wire after I got the carb removed from the MS170 and was going to investigate a quick connect when re-installing the new carb.
 
And I have fat sausage fingers and I have no problem working on them, just use your brain and some good tools rather than just muscles to do the job haha

Right: Keep a heads up and take care removing and installing the snap out/snap in plastic choke/kill switch shaft rod! (it will operate somewhat freely without being forced when it's installed correctly) Watch the spring loaded metal kill switch lever for proper position in the steps on the plastic shaft when the shaft snapped is back into place. It appears that if the metal kill tab is not in proper place in the steps when re-installing the plastic shaft something could be easily broken when applying choke or kill position of the kill lever.
 
Just general MS170 info:

I'm working on two MS170's with fuel issues! One is bogging, other one would not idle until several CW turns of the idle adjustment.

Carb is easy to remove! 8mm socket and a torx to remove plastic cover on handle for throttle linkage access then remove kill wire and the plastic choke shaft and you are there.! OEM Zama carb C1Q 057A is bogging.

Ordered a Zama carb replacement yesterday from STIHL DEALER. 1130 120 0603@ $28 and a fuel hose 1130 358 7701@ $5.99. I can see damp gas on the outside of the old fuel hose.

See cheaper parts on flea bay but, Cannot bring myself to trust ebay for parts when it says from China.
I have purchased the real cheap ebay China chainsaw carbs just as a test carb to see if a expensive OEM Stihl chainsaw carb is the problem and if Chainsaw responds ok I go to work on the OEM carb, usually run it thru a ultrasonic leaner and then kit if replacement carb is costly. If carb happens to be one of the harder ones to remove and install I'll go for replacement rather than taking chance of having to kit, re-install, test and possibly remove again. (time repairing vs cost of complete carb replacement)

I don't leave a cheap China $10 carb on a high priced good saw.

There is a small hole thru the side of the black handle to adjust the idle speed with a very small screwdriver on these two MS170's. The idle adjustment is kinda slow to respond. Several turns of the screwdriver to get a throttle response. No H and L adjustments.

You need to look at the spark arrestor screen. (remove the 8mm nuts on the front of the muffler and it's right behind the little front plate) These two saws screens were clean but I've heard rumors of the 170 screen clogging mainly due to mixing too much oil in the gas. Saw will start bogging after it gets warmed up similar to carb/fuel issues.

Here is a link for the MS170 owners manual with some good info! The idle adjust says it Left hand thread, but the idle adjust instructions indicate it's RH thread??? (pg 41)

https://www.stihlusa.com/WebContent...TIHL-MS-170-180-Owners-Instruction-Manual.pdf
 
It is a left hand thread, you turn it left to screw in and right to back out for higher idle speed.
 
MS170s suck, my ex girlfriend purchased one, never could get it to start and run right. It was EZier for me to just break up with her then it was to work on that thing! haha

if I owned one, I would admit I had a POS, dump it for parts. Then buy an Echo
 
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