Ms170 hard to start. Choke doesn't fully close

[HarleyT]

Still need some pics, hard to help otherwise.

 

[etbrown4]

Op here. I'm 200 mi from my saw for a week, so Ill post pics in a week upon return.

I didn't try to manually close the factory choke, or on the replacement carb i fitted in place, but didn't leave in place because they both looked the same, but can try both soon enough.

I wasn't referring to any white plastic. I might be off on this because I didn't really study it, but I dont recall a seperate intake manifold. What I remember is I removed the air filter box and then the carb. I only recall seeing a 2 hole gasket, still on the side of the cylinder, to which the carb was bolted. Again, I could be wrong.

I think there's a high chance that both of those choke butterflies will fully close manually, but I'll verify .

If it is true as one poster said above, "This is a common problem on 034 because of the design, " then it could be a widespread issue making lots of these saws hard to start.

 

[HarleyT]

There should be no gasket, the carb fits against the rubber intake boot. There should be a white plastic expander ring, but that fits into the recess.

 

[stihltech]

Not a widespread issue on a MS170. It can be corrected. Widespread issue on an 04/036. Much different choke linkage.
Lets keep it apples to apples when comparing.

 

[ZeroJunk]

The linkage fits in a hole in the control handle. And, when you push the lever all the way down a flat extension on the shaft facing the carb pries the choke linkage up.

So, is the throttle control lever staying all the way down, or is it popping back up ?
If it is staying down then either the choke linkage is bent, or wasn't right to start with.
Or, the choke shaft has slipped inside the lever on the end of it.
Or, the plastic extension that the choke linkage is pried up by his worn or wasn't molded right.

 

[woojr]

This is no help but another option. I bought a used 026 with a new carb off Ebay around 15-20 years ago. I was much younger and could start it after about 12 full choke pulls. It would then start first pull after it warmed up. After my second back surgery four years ago I needed less choke pulls. I put a new carb and fuel lines, filter, etc. Still needed a dozen yanks full choke. I don't don't use it that much these days but now I just pop the air filter cover, pour a little gas down the carb throat and it fires right up and runs great. it has been one of the best saws I've owned for small medium cutting. Really lightweight and good power.

 

[etbrown4]

Here we go.
Pic of the carb with choke mostly closed as far as it could pic#3, and linkage before tweaking pic #1, and what looked like a gasket behind carb. (note: with carb nuts removed the carb will shift forward slightly and open the choke 1/4" on its own pic#2, but that is not the problem)

Sure enough, pic#3 reveals a minor factory defect as the choke from the factory would not close the last 1/16-1/8". Left alone, it was going to be flooding prone as I waited for the pop.

I bent the linkage just enough to fully close the choke when reassembled. It popped on the 3rd pull, then started.

All I can say is shame on Stihl as this should have been caught at the factory! Really no excuse. No telling how many lousy starting Ms170s and 180s are out there. And this saw was made in Va Bch, Usa!

 

[SteveSr]

Here we go.
Pic of the carb with choke mostly closed as far as it could pic#3, and linkage before tweaking pic #1, and what looked like a gasket behind carb. (note: with carb nuts removed the carb will shift forward slightly and open the choke 1/4" on its own pic#2, but that is not the problem)

Sure enough, pic#3 reveals a minor factory defect as the choke from the factory would not close the last 1/16-1/8". Left alone, it was going to be flooding prone as I waited for the pop.

I bent the linkage just enough to fully close the choke when reassembled. It popped on the 3rd pull, then started.

All I can say is shame on Stihl as this should have been caught at the factory! Really no excuse. No telling how many lousy starting Ms170s and 180s are out there. And this saw was made in Va Bch, Usa!

Something looks "fishy" with that throttle linkage. That throttle rod should push forward to open the throttle on full choke. The the kink in the rod appears to be on the wrong side of the throttle shaft.

The correct operation should be as follows... Squeeze the throttle and then push the lever all the way down to choke. This sets choke and part throttle. Move lever up one notch. Choke opens and part throttle stays. Blip the trigger and the lever should pop up to idle and the part throttle should be released.

In the photos it looks like the "kink" in the throttle rod is on the wrong side of the "flag" on the control rod. The throttle rod may be in backwards or may be the wrong one.

 

[AxFan20]

Have a nearly new ms170 and yes I know you pull it until it pops then slide to half choke.

Problem is that at full choke it sometimes wont pop, no matter how many pulls. And you have to assume that continued pulling likely creates flooding.

Yes I have a new plug, good blue spark, clean filter, new gas, a clean carb and plenty of compression..

I mounted up a new carb and see that if used, it also doesn't fully close at full choke.

Anyone studied this enough to find a way to fully close the choke, and see if that helps starting

The choke linkage does not work entirely by length. The linkage is pushed sideways by the little black 'shelf' where the linkage is attatched. Watch the linkage close the choke in motion back and forth. Your linkage is in the middle of the slot on the carb control arm when fully closed.. Bend the linkage a little, very little, tighter at its bend, to make it end up a little farther right at the carb. When it is fully to the right in the 'slot', it will close the choke completely and solve your issue.

 

[SteveSr]

Here we go.
Pic of the carb with choke mostly closed as far as it could pic#3, and linkage before tweaking pic #1, and what looked like a gasket behind carb. (note: with carb nuts removed the carb will shift forward slightly and open the choke 1/4" on its own pic#2, but that is not the problem)

Sure enough, pic#3 reveals a minor factory defect as the choke from the factory would not close the last 1/16-1/8". Left alone, it was going to be flooding prone as I waited for the pop.

I bent the linkage just enough to fully close the choke when reassembled. It popped on the 3rd pull, then started.

All I can say is shame on Stihl as this should have been caught at the factory! Really no excuse. No telling how many lousy starting Ms170s and 180s are out there. And this saw was made in Va Bch, Usa!

This photo is WRONG! The throttle rod should be in FRONT of the lever holding the throttle part way open. It shows OPERATOR ERROR in trying to engage the choke WITHOUT depressing the trigger!

This is NOT how the mechanism is supposed to work. It leaves the throttle closed and the choke partly open for a hard/no start condition. If you want to watch how the mechanism is supposed to work get some spacers from the hardware store to bolt the carb in the proper position and don't forget to RTFM!

 

[etbrown4]

Will try it the other way!

 

[etbrown4]

It appears the black throttle plastic tab will move above or below the throttle linkage on its own depending on the throttle and choke settings. However if you depress the throttle and then set the choke, the tab will move to the front side.

Either way, this choke, with either throttle/tab position, was failing to fully close, and a tweak to the choke linkage has fixed that.