Stihl MS170 woes

[Ken12]

I aquired this little 170 for a song not long ago. The issue is that the saw will not run with the air filter box installed. Remove the box and she runs like a champ. Seems to be choking out the saw when installed. I had another used carb that I tried to no avail. Same with the new carb. Compression is good (140) and the choke plate is free and clear of obstruction. I have done/tried everything I know to do. Anyone have any ideas or have had this happen to them? Thanks in advance.

 

[HarleyT]

What happens when you run it with the box installed, but the top cover removed?

 

[stubnail67]

try washing and drying the airfilter?

 

[sundance]

Tried a new air filter?

 

[Ken12]

It's not the air filter. I have removed it and I get the same results. I'm really stumped on this one.

 

[Ken12]

What happens when you run it with the box installed, but the top cover removed?

I get the same result no matter what I do unless I completely remove the box and bolt the carb up without it. She runs like a champ then. I'm at a loss here.

 

[Full Chisel]

Have you tried adjusting the carburetor?

 

[HarleyT]

I get the same result no matter what I do unless I completely remove the box and bolt the carb up without it. She runs like a champ then. I'm at a loss here.

Well, the filter box itself must be closing or blocking the choke, because with the top off, the air filter is "bypassed".

 

[HarleyT]

Can you put up some pics?

 

[Conquistador3]

Remove the spark plug, take a very good picture of it and post it here. That should say if it's running too rich.

Also check if the the air filter cover is genuine or otherwise: on B&S engines it's not uncommon for poorly made aftermarket filter covers/housing to cause enough air flow disruption as to result in a non-running condition.

 

[Ken12]

I think I figured it out. This whole time I have tried it without the orange top cover. I put the top on and she fired up! Is this common to these saws?

 

[Khntr85]

Something must have been in a bind...

 

[HarleyT]

Actually, the top cover just seals a chamber above the air filter, so the air must come up through the box, through the bottom of the filter, into the chamber, then down into the carb throat.

 

[Khntr85]

I meant more around the throttle linkage area.... I had a guy want to trade me a new ms180 for a 180 I had.... I said let me see your saw.....turns out his kill switch lever was just bent some and the throttle linkage was bent....could have really stuck it to him, but I ain't into that, just fixed it for the old guy and he was thrilled!!!!

 

[HarleyT]

Yeah, those models have had some problems in that area, like the master throttle lever popping out of its holder.
That is why I was asking for pics.

 

[Khntr85]

Yeah, those models have had some problems in that area, like the master throttle lever popping out of its holder.
That is why I was asking for pics.

Yes sir, excactly what I was thinking when I started reading this.... as you stated the cover is basically just to hold airfilter down and direct the air flow....

I have also seen the throttle linkage bind up when the saw is held like you would be making a felling cut on a tree....