Stihl Chainsaw dies after few second or under load

Stihl Chainsaw dies after few second or under load

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Tampon

Original Poster:

4,637 posts

225 months

Sunday 8th February 2015
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I have had the saw for a year or so (bought secondhand) it has been brilliant. (It has a non adjustable Carb)

Last few times I used it the saw needed revving up before cutting or it would bog. It died last week cutting some wood. It would catch slightly when warm but nothing else.

It will start cold on full choke and rev its nuts off on half choke but touching the throttle will kill it.

I bought replaced the carb for a new one, I have removed the fuel filter (to check it isn't blocked), cleaned the old carb (tried both and same result) it has fresh fuel, spark is good and spark plug is clean, air filter has been cleaned, there is no spark arrestor on the exhaust to be blocked (made that mod straight away).

Even after all this (and trying both new and cleaned Carb) I have the same issue, will run on full choke for a while, will rev its nuts off on half throttle, occasionally idle off throttle but not for long. Saw always dies.

I am thinking there is a slight leak in the fuel line which shows up under load (saw is about 10 years old and the line is very soft)

Apart from that I am out of ideas. Any thoughts?

I have a full service kit of new filter, spark plug, fuel filter, fuel line, oil line etc on its way. Thought I would ask to see if there was anything I had missed?

kev b

2,714 posts

166 months

Sunday 8th February 2015
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I had a similar problem last year with a different make. The cure was to cut a slot in the two "tamperproof" mixture adjusting screws and tweak the mixture.

There are guides on the net for Ryobi, your Stihl is likely to be similar, I cut the slots with a dremel or you can knock a piece of tubing over and turn them that way. HTH

Tampon

Original Poster:

4,637 posts

225 months

Sunday 8th February 2015
quotequote all
kev b said:
I had a similar problem last year with a different make. The cure was to cut a slot in the two "tamperproof" mixture adjusting screws and tweak the mixture.

There are guides on the net for Ryobi, your Stihl is likely to be similar, I cut the slots with a dremel or you can knock a piece of tubing over and turn them that way. HTH
Cheers, will have a Google. Still thinking it is more fuel delivery under load, so will change everything (not least because it is just fun to play with engines) then give your idea ago if it doesn't work.

Thanks.

T1pper

275 posts

136 months

Sunday 8th February 2015
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I think I had a similar problem about 20 years ago IIRC it was a blocked exhaust, as it was 2 stroke it tended to clog up.

TvrJohn

1,058 posts

255 months

Sunday 8th February 2015
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how about coil failure under load ?

Tampon

Original Poster:

4,637 posts

225 months

Sunday 8th February 2015
quotequote all
TvrJohn said:
how about coil failure under load ?
How could you test for that? replace with a known working coil?

longshot

3,286 posts

198 months

Sunday 8th February 2015
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Ask on here...

http://arbtalk.co.uk/forum/

There's a forum half way down for chainsaws.

bonzza82

12 posts

138 months

Monday 9th February 2015
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Hi
It sounds to me that it is the bearing seals on the crank, and possibly the crankshaft bearing themselves, you would have to take the pull cord off assembly off to check for crank movement,

CrutyRammers

13,735 posts

198 months

Tuesday 10th February 2015
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kev b said:
I had a similar problem last year with a different make. The cure was to cut a slot in the two "tamperproof" mixture adjusting screws and tweak the mixture.

There are guides on the net for Ryobi, your Stihl is likely to be similar, I cut the slots with a dremel or you can knock a piece of tubing over and turn them that way. HTH
I "inherited" a Stihl which was not running. After stripping and cleaning it did what the OP describes, and did indeed seem to be the mixture that was wrong. The screws are not tamperproof on mine and easy to tweak, I got it back to running easily enough and used it for a couple of years.
That said now it's stopped working and won't even start now frown. Another thing on my big list of things to fix.

Also check that the chain isn't binding as I had similar symptoms on our Ryobi when the oiler went (the plastic drive gear stripped so no oil was getting to the chain). That caused it to stall every time; I'm told (though I haven't checked) that Stihl also use a plastic drive for the pump. If you take the bar off and run it, you can easily see if it's pumping oil.

Tampon

Original Poster:

4,637 posts

225 months

Saturday 21st March 2015
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Update - I hate it when people ask for help and don't post up the end result.

It was the fuel line, the saw sat in the shed in bits until I got home from work last night and bought a mower to fix up as the grass is growing. After finishing servicing the mower I had a go at the saw.

Replacement was straight forward and i put the original carb back on as I had cleaned it. So now I have a spare cheapy one when this one needs a service kit putting on.

The mower started up 4th pull and ran perfectly.