Stihl Ms 170 Carb

[djg james]

I'm now working on my 170. It starts, but you have to keep pulling the throttle to keep it running. I had a fuel filter so I put that on. It acted the same. I took the carb apart and soaked, but still no go. So I was either thinking putting a aftermarket carb kit on or an aftermarket carb. Does anyone use these cheap aftermarket carbs or would you rebuild the original Stihl carb?

https://www.ebay.com/itm/Carburetor...210678?hash=item1a3957e2b6:g:o4IAAOSwMQBaAA1Y

 

[DND 9000]

In most cases it is better to use a new carburetor. These fixed jet carburetors are difficult to get clean and working properly again. Maybe you casn also find an adjustable one. I`m not sure now but maybe the Walbro WT-215 works. Maybe others chime in with more knowledge about this.

 

[Ando81]

There is another thread about putting the Walbro carb onto Ms170 saws. I put an aftermarket copy of the Walbro 215 on my Ms170 and it’s great, easy to tune and runs really well [emoji1305] It took me about fifteen minutes to remove the old Stihl carb and to install the aftermarket carb.

 

[djg james]

Thanks, I'm reviewing all the old threads. Is a Walbro type carb better the the original type? I admit, I don't know how to tune a carb.

 

[Ando81]

I’ve had trouble with my saw not wanting to rev with the Stihl carb and a work saw had the same issue. I always try to keep the air cleaner spotless but it’s a terrible design how it seals to keep sawdust out. The Walbro style seems quite good. You can get instructions on YouTube how to set a basic tune for your saw then tweak it to suit yourself from there. Every carb will need to be tuned differently so you need to adjust your own or get someone to do it for you. Your main concern is to avoid it running too lean and causing piston damage.

 

[djg james]

Well, I messed with the carb again today. I had previously taken off the two plates and the needle and soaked in toluene. Suppose to be better at dissolving gunk than mineral spirits. Put it back together and it still wouldn't run right. So today I pulled both covers AND the little screw holding the spring and pin down and soaked everything again. MISTAKE! Putting that spring back with the little pin was a PITA! Naturally, I lost the spring on the concrete floor not once, but twice. Then the pivot pin and the conical pin. Finally after finding everything a last time, I put white paper on the floor to start the assembly. After all that's where (floor) all the parts wanted to be. Multiple attempts were made to get all in the right place to put that little screw in. Bad hand so I finally used small strips of duct tape (modern day bailing wire) to hole the pins and the spring in place. Finally got the saw reassembled.

The saw started up and ran strong, but only at 3/4 throttle. I've got some limbs to cut up tomorrow to see if the saw bogs down under load. But I don't understand why the saw starts to sputter when the throttle is pulled all the way. Pluggage still there or re-tuning? If problems persist, I'll just opt for an aftermarket carb. I know you recommended a Walbro, but I think I'll put the same style on. As you can tell, I don't have the experience you guys have and I don't feel comfortable drilling new tuning holes and trying to tune it. Keep it simple for me.

 

[Ando81]

They can be a nightmare to work on when parts decide to vacate the area. Imagine me doing it with a gravel driveway trying to find dropped screws. Foolish of me I know. Anyway I am guessing that saw may be struggling to rev above 3/4 might be lack of fuel because as soon as you open the throttle and only air comes in and not enough fuel makes it die. By the way, I tuned my Walbro carb on my 170 with the cover off without drilling holes and it worked ok. I did end up drilling 2 holes about 4mm for future tuning.

 

[djg james]

I had previously put a new fuel filter on, so I don't know where it could be starving it from fuel. I will play with (1/4 turns) the one adjustment screw on the carb tomorrow.

 

[HarleyT]

That screw doesn't do anything with the fuel mix.
Take it back apart and remove the little brass jet, and make sure it is clear/clean, it takes a small flat tipped screwdriver to remove. It is Part# 2 or #30 in the pic here.

 

[HarleyT]

Here is a manual to help you.

 

[Ando81]

Thanks for sharing the manual, this will help me to fix a saw at work that isn’t revving to its full potential. I didn’t want to put another carb on the work saw, now I can fix it properly.

 

[djg james]

Is part #2/30 that you are talking about under part #3? If so, Oh Hell no I'm not going to take that apart again! Seriously I do believe I remember seeing that but didn't remove it. If I still have problems, I'll give it a try one last time.

if it doesn't adjust the fuel, what does part #23/24 do?

 

[HarleyT]

Idle speed adjustment screw.

You have the jet #2, it is beside the spring/lever/needle thingee.

 

[djg james]

Idle speed adjustment screw.

You have the jet #2, it is beside the spring/lever/needle thingee.

Thanks, beside is good. Nothing under to pop out at you s there?

 

[HarleyT]

The manual is more for the older 017, which some had a low speed mixture screw. Your carb doesn't have any mixture screws, but a fixed jet.

 

[HarleyT]

Thanks, beside is good. Nothing under to pop out at you s there?

No, but it is easy to lose.


I was going to come up with a joke about something popping out at you,

but maybe some other time.

 

[HarleyT]

Any bit of scum/crud will make the saw run poorly. It is a shame that there are no adjustments, as you could probably just get by with richening up your adjustments, and go cut wood.

 

[Ando81]

I believe there isn’t and adjustment screws because the saws are made for home use. Stihl didn’t want the handy hubby trying to “tune up” the saws and melt piston rings etc from running too lean.

 

[djg james]

No, but it is easy to lose.


I was going to come up with a joke about something popping out at you,

but maybe some other time.

After messing with that spring/lever/needle thingee, I could use a joke.

 

[HarleyT]

After messing with that spring/lever/needle thingee, I could use a joke.

Yeah, that is why most guys just buy a new carb!
Here is the price for a brand new carb from the Stihl dealer:
1130 120 0603 CARBURETOR $22.16