Still MS170 chainsaw hard to start & doesn’t run long

[ipbr21054]

Just noticed H and L holes which mine don’t have

 

[ipbr21054]

Just looking at a video and see H and L on his also but they must be blanked off.
Now need to go check mine again.

 

[Burnerman]

So many carburettor variations - some have mixture screws, some don't.
This is a very popular carb with the smaller Stihl chainsaws so plenty replacements are available.
John

 

[ipbr21054]

Ive taken mine apart again & i now do see the holes BUT they are not threaded, So never a jet fitted just a hole & it looks like either a small brass fitting with a hole or just a blank at the bottom.

Ive taken carb apart again & cleaned it but pretty much clean.
I took the chain side cover off & was covered in fine sawdust / bar oil so cleaned it up.

I think i might of nudged the poor design filter a touch when putting on the top cover as when i did this yesterday i made sure it was spotless but this morning i could see a small amount of sawdust in that black plastic part which holds the car to the engine.

Yet to start it but will do very soon

 

[Deluks]

Not an engine expert, but my Stihl chainsaw exhibited similar symptoms a few years ago. Changed the coil pack, all resolved.

 

[ipbr21054]

10 pulls but nothing in the way of you thinking it will start.
Added a drop of carb cleaner down air filter port, choke on then 2nd pull it wanted to start.
Choke off then 2nd pull it started & kept running.

Ive left it running now 5 minutes & seems ok.

So if coil or plug was an issue i assume the starting / running of the saw wouldn't happen ?

Did i just clear out a partial blockage & that's why it now runs or advise why 10 pulls & nothing but carb cleaner it then starts ok ?

Carb, Plug, Filter & Coil in post anyway but just wanting to learn from this

SHORT VIDEO CLIP

 

[Burnerman]

Nothing can be proved here, but simply you gave the machine the correct fuel / air mixture that it liked......on two strokes, fuel is ingested into the crankcase first before being burnt above the piston. Fuel that condenses in the crankcase can cause a rich mixture, which your cleaner spray dealt with. - hence the start up.
I don't know what your technique is, but always use full throttle, hot or cold.
If the machine is clay cold, always use the choke. If it's slightly warm, choke may again be needed (one pull only) to get it going again.
It's what the word 'temperamental' was invented for!
you'll rarely see any blockage in these carbs, but the diaphragms do weaken with age and fuel......and that you can't tell.
John

 

[ipbr21054]

So reading your reply above i might have found the issue with the starting.

When i start the saw i move the black lever to the bottom position.
I pull it over until it tries to start.
Once i hear it try to start then i move the black lever to the upper position shown.
I pull it over until it then starts.

I do this WITHOUT touching the throttle lever hence maybe my starting issue.

With regards it stalling after say 5 minutes twice on last job i think it must be down to the fine sawdust ?
Think ive sorted out the diaphragms question as it sat there quite happy ticking over for 5 minutes.
If it was an issue i would expect it to play up but it didnt.

Thanks

 

[Burnerman]

That starting technique is correct.......if you touch the throttle when the choke is set the throttle may well spring back - defeating the object!
If the machine seems flooded, set the lever to I and have full throttle on - a few pulls should clear it.
John

 

[ipbr21054]

So i read you reply wrong.

When you wrote **I don't know what your technique is, but always use full throttle, hot or cold.**

You mean when the saw IS IN USE

 

[Burnerman]

Errr no - just when starting up!
If you are just lopping small branches there's no need to rev the thing flat out.
If the bar is completely deep in a log, you'll need full throttle though.
John

 

[ipbr21054]

Confused.

I didnt use throttle lever at all only choke when starting

You mentioned full throttle then next reply said no or it defeats the object.
So when you using full throttle that you mention

 

[Burnerman]

When you move the lever right down to the full choke position, the throttle is automatically set by the linkage behind the orange cover.
John

 

[ipbr21054]

New coil & Carb here & now fitted.
Same start up procedure as mentioned before.

Now with this new carb which is a very good chinese copy & cant get it to run.
It starts & as soon as i use the trigger it stalls.
Do i turn screw in or out for it to keep running.

Bearing in mind i have no idea to what its currently set at

 

[ipbr21054]

Ive now got it started after a fashion but after i let it warm a little then try & give it a rev it bogs.

I have tried the following but still the same.
Tried it with air filter off.
Tried it with fuel filter off.
Tried new plug.
Let it warm up longer.

Spark arrester is clean & not blocked / gummed up.

I screwed the idle screw right in then 2 turns out & then this is where i start from
After letting it warm up i turn the idle screw one way 1/4 of a turn then again then again but it starts to want to stall.

I then do then same again but the other way this time.
At a certain point i then see the chain start to rotate on the bar so now i tell myself ive done it too much then i go back the other way until bar slows / stops.

This is done with putting screwdriver through handle & side of carb casing.

It seems to want to tick over ok but i have to tickle the throttle lever before i grab it to get revs right up.