Need help with MS 170

[Quickhorse]

Working on an MS 170.

It is an MS 170 with a 14" bar/chain . . . it had a broken case where the lever for the throttle snaps in so I transferred everything over to another case. The saw started but didn't run good on wide open. It wasn't quite getting to the top rpm's. I took the spark plug out and cleaned it. Also sprayed some carb cleaner in. The saw just doesn't want to stay running. Any ideas? should i just put a new carb on it? Is there a jet adjustment on these or do they come preset?

Any help would be appreciated . . .

 

[NewToStihl]

Did it run fine before you replaced the case, or did your repair make a difference in how it runs?

I believe the only adjustment you can make on the MS170 model is the idle adjustment - the H & L are fixed jet.

 

[sefh3]

I would try a carb kit. How does your fuel line look?

 

[Quickhorse]

I would try a carb kit. How does your fuel line look?

Fuel line seemed fine . . . do they go bad usually? Not sure if there is a carb kit . . . i think you just replace the whole carb.

 

[o8f150]

get you a wt 215 carb and put on it and not look back,,, here is mine

<iframe width="560" height="315" src="http://www.youtube.com/embed/Sr4oqOVyjfE" frameborder="0" allowfullscreen></iframe>

 

[Quickhorse]

get you a wt 215 carb and put on it and not look back,,, here is mine

<iframe width="560" height="315" src="http://www.youtube.com/embed/Sr4oqOVyjfE" frameborder="0" allowfullscreen></iframe>

Where did you buy that carb at ebay? Local dealer? Nice . . . that's exactly why I wanted to fix and keep this saw instead of tossing it. Last night i had to use my 310 to cut some logs into smaller pieces . . . it was 10pm and i have the muffler mod done to it . . . i felt like all the animals in the woods were staring at me saying . . . "seriously" . . . lol

 

[NewToStihl]

Let's try this again . . . did it run fine before you worked on it?

 

[o8f150]

Where did you buy that carb at ebay? Local dealer? Nice . . . that's exactly why I wanted to fix and keep this saw instead of tossing it. Last night i had to use my 310 to cut some logs into smaller pieces . . . it was 10pm and i have the muffler mod done to it . . . i felt like all the animals in the woods were staring at me saying . . . "seriously" . . . lol

you can find them on fleabay,,, i got several here just for that reason,, i run into a lot of 170's around here

 

[Quickhorse]

Let's try this again . . . did it run fine before you worked on it?

It ran better than it does now . . . but still crappy.

 

[sefh3]

Make sure your carb boot doesn't have a hole in it.

 

[NewToStihl]

Slapping a new carb on it may very well fix the problem, but it might not. If it runs worse now that you're worked on it there is at least some issue you introduced. Make sure all of the lines are properly installed and clean. Make sure the air filter is clean. Make sure the spark plug is not only clean, but gapped properly. Make sure the tank vent is not clogged.

There is more to cleaning a carb than spraying some cleaner in it. You'll need to completely disassemble it and meticulously clean the valve seat, diaphrams, screen, ports, and orifices.

Does it idle smoothly? Does it only run badly when throttling up? Does it choke/die out, and if so, under what circumstances? Do you have properly mixed, fresh fuel in it?

 

[Quickhorse]

Make sure your carb boot doesn't have a hole in it.

I'll check that . . .

Slapping a new carb on it may very well fix the problem, but it might not. If it runs worse now that you're worked on it there is at least some issue you introduced. Make sure all of the lines are properly installed and clean. Make sure the air filter is clean. Make sure the spark plug is not only clean, but gapped properly. Make sure the tank vent is not clogged.

There is more to cleaning a carb than spraying some cleaner in it. You'll need to completely disassemble it and meticulously clean the valve seat, diaphrams, screen, ports, and orifices.

Does it idle smoothly? Does it only run badly when throttling up? Does it choke/die out, and if so, under what circumstances? Do you have properly mixed, fresh fuel in it?

I was meticulous with re-assembly . . . amsoil mix for fuel, amsoil bar chain oil, cleaned and gapped plug, etc . . . I'll have to check the tank vent. does it vent through the cap or is there an actual line on these?

It only idles when it wants to . . . runs fine when throttling up just wimps out when it gets close to full rpm range.

 

[sefh3]

make sure you have the plastic spacer between the carb and boot.

 

[sefh3]

Pull the muffler and look at the screen inside the muffler and look at the piston.

 

[NewToStihl]

On those there is a small rubber duckbill valve on the top of the fuel tank. If memory serves me you can't see it unless you actually pull the tank out of the case a bit. If possible, full the fuel line off of the carb and apply a little bit of vacuum - the vent should not allow vacuum to build up . . . obviously.

 

[ROWDY]

I agree with everyone above that you most likely have a fuel restriction someplace.

 

[NewToStihl]

Pull the muffler and look at the screen inside the muffler and look at the piston.

Good call on the spark arrester screen . . . for some reason I've seen a lot of 170's with clogged screens.

 

[sefh3]

Good call on the spark arrester screen . . . for some reason I've seen a lot of 170's with clogged screens.

Usually these are homeowners that run these saws. They let it idle and run for short periods. It doesn't run long enough to burn the carbon off the screen.

 

[Fish]

A common problem on these saws is cracks in the fuel line above the tank. Also, the newer fuels can make the fuel line soft and gummy so it pinches shut and sticks together when running.

If either condition is found, a complete carb cleaning is needed as well.

 

[Quickhorse]

make sure you have the plastic spacer between the carb and boot.

I do . . .

On those there is a small rubber duckbill valve on the top of the fuel tank. If memory serves me you can't see it unless you actually pull the tank out of the case a bit. If possible, full the fuel line off of the carb and apply a little bit of vacuum - the vent should not allow vacuum to build up . . . obviously.

I'll try that . . . it's definitely a fuel problem b/c it starts under full choke/throttle . . .