Stihl MS170 chainsaw problem

[weirdfish]

Hopefully this is alright in this section.
Stihl ms170 chainsaw, works ok for roughly half tank of fuel then just bogs down under load.
I’ve replaced the plug, air filter, fuel filter and drained and replaced the fuel with fresh stuff mixed as per instructions.
Before I take it down the local dealer, ( which I hate doing ), any pointers as to what to look at.

 

[CPS]

Hopefully this is alright in this section.
Stihl ms170 chainsaw, works ok for roughly half tank of fuel then just bogs down under load.
I’ve replaced the plug, air filter, fuel filter and drained and replaced the fuel with fresh stuff mixed as per instructions.
Before I take it down the local dealer, ( which I hate doing ), any pointers as to what to look at.

The little fuel hose that goes into the tank is probably perished

 

[weirdfish]

The little fuel hose that goes into the tank is probably perished

Are you thinking that as soon as the fuel runs low the pipe is not carrying the fuel to the carb?

 

[weirdfish]

To answer my own question, just filled the fuel tank and it still bogs down.

 

[doobin]

Just get a £15 Chinese carb off ebay and swap it out. Do the hoses whilst you're in there. Ten minute job tops.

 

[V8Druid]

I have a Stihl that does a similar thing - it has a tiny gauze in the carb which literally 'gums up' ... strip carb and clean the filter and is ok for a while then it's the same again --- what blocks the filter is like the finest of talc in suspension with the fuel -- I've virtually sterilised the tank and it still does it -- new lines, filter, etc. -- of the opinion that some how the finest of dust is getting into the system some where

 

[V8Druid]

Just get a £15 Chinese carb off ebay and swap it out. Do the hoses whilst you're in there. Ten minute job tops.

do you have a fave seller for these wonder carbs, you're always extolling Doob .... bought one for my Flemng's Hodna 5.5 and can not get it to run tidy

 

[doobin]

do you have a fave seller for these wonder carbs, you're always extolling Doob .... bought one for my Flemng's Hodna 5.5 and can not get it to run tidy

For Honda carbs I always use LS Engineers. A few quid more but I've never had an issue with them.

 

[V8Druid]

For Honda carbs I always use LS Engineers. A few quid more but I've never had an issue with them.

thank you Doob

 

[CPS]

The little fuel hose that goes into the tank is probably perished

Are you thinking that as soon as the fuel runs low the pipe is not carrying the fuel to the carb?

I was thinking that, my little cheap saw was like that til i changed the hoses.. but i thinknyou have eliminated that.

I have a stihl that does run roughly at the start.... though i put that down to lack of use

 

[V8Druid]

I was thinking that, my little cheap saw was like that til i changed the hoses.. but i thinknyou have eliminated that.

I have a stihl that does run roughly at the start.... though i put that down to lack of use

mines like a demon -- 'til the bloody gauze gums up

 

[Lancs Lad]

thank you Doob

You'll not go wrong with L&S

 

[Stock]

Might be a coil issue when they heat the insulation breaks down causing issues................................................................................. but I'm not a stihl man .........................................................

 

[Lancs Lad]

You more of a dot man?

 

[weirdfish]

I have a Stihl that does a similar thing - it has a tiny gauze in the carb which literally 'gums up' ... strip carb and clean the filter and is ok for a while then it's the same again --- what blocks the filter is like the finest of talc in suspension with the fuel -- I've virtually sterilised the tank and it still does it -- new lines, filter, etc. -- of the opinion that some how the finest of dust is getting into the system some where

Where is the gauze in the carb, can’t remember seeing it.
I might just bite the bullet and get a new carb/coil/fuel pipe, for the sake of £20 it’s got to be cheaper than a visit to the local dealer, ( stihl dealer that is ).

 

[Lancs Lad]

Where is the gauze in the carb, can’t remember seeing it.
I might just bite the bullet and get a new carb/coil/fuel pipe, for the sake of £20 it’s got to be cheaper than a visit to the local dealer, ( stihl dealer that is ).

If your really stuck...jump on atbtalk I'll bet spuds answered a similar issue on there before. He knows his stuff TBF ... to be blunt unless it's a cheap fix you can sort yourself you'll be cheaper replacing it than taking to a dealer.

 

[doobin]

Where is the gauze in the carb, can’t remember seeing it.
I might just bite the bullet and get a new carb/coil/fuel pipe, for the sake of £20 it’s got to be cheaper than a visit to the local dealer, ( stihl dealer that is ).

Gauze in the carb is under the top plate. Take carb off remove plates too and bottom and there’s a membrane (which also needs cleaning) and under that is a port with gauze.

And if you cant get it back together (although a five year old should be able to!) or it doesn’t work still, put a new one on!

It could well be resinous deposits deep inside the carb from ethanol in the fuel, and even an ultrasonic clean won’t shift them.

 

[V8Druid]

Where is the gauze in the carb, can’t remember seeing it.
I might just bite the bullet and get a new carb/coil/fuel pipe, for the sake of £20 it’s got to be cheaper than a visit to the local dealer, ( stihl dealer that is ).

these took some finding ... you can see the issue though

and before anyone says dirty fuel/tank/lines .. clinically cleaned - twice and new lines / filter pick up

 

[weirdfish]

Well, not sure what the actual problem was, but, after removing the carb and taking the top and bottom off, cleaning, ( no real dirt ), refitting cleaning everything as I went.
Started up and revved its bloody head off, adj the idle speed and all seems well.
The real test will come when I cut some more logs this week.
Thanks for all the pointers

 

[weirdfish]

So, it lasted longer than before but ended up full of very fine dust again resulting in bogging down under load.
Stripped cleaned and running as it should.
Surely it shouldn’t block up this quick?
Am I missing something from the air filter area that’s allowing all the dust in?
Should there be 2 parts to the filter?