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Help with chainsaw please


nb celestine

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Hello, I bought a well used Maculloch chainsaw years ago for £40 as I was only going to use it every few months or so. It's done ok, but now it starts after a while but cuts out after a few log cuts.

    I don't want to spend a fortune servicing it, as I'm thinking of getting a new Stihl if this one has had it. So, I've put a new plug in, new correct ratio fuel, and I'm just about to buy a new coil and fuel filter for it.

  So I want to know, when I replace the coil, do I push the magnets tight against the drum or do I leave a very slight gap? I think when I removed the old coil, it was tight against the drum but I'm not sure.

   I did think of taking the carb off and checking the membrane but I'm a bit fingers and thumbs so thought better of it.

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Do you mean what you ask? The magnets should be attached to the flywheel.  The coil should have a very slight gap between it and the spinning magnets.

 

Here's a video...

 

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2 minutes ago, nb celestine said:

Just watched the video. I was wrong, I thought the magnets were on the coil not the flywheel. 

    Thanks for the replies.

     I wish my saw was as clean as that one. 

Tsk, clean it then or I might give RSPC a call

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Nothing like internet trouble shooting but 'to me' it doesn't sound like an ignition issue. Fuel filter is a good call.

Does it start back up after it stops or not?

Did you check to see if has spark when it stops?

 

Typically the carburetor is the main source of problems. Ignition usually just fails and never works. It can fail when hot but sort of unusual. That is why I was asking if you had spark with it stopped.  

 

Someone gave me a older Husqvarna recently. First check was did in have compression.  Then spark and then I tried to crank it. Wouldn't run so I just ordered a new carb and it runs like new. Carb is just so ofen the issue it not worth trying to clean them.  We used these, leave them with gas in the carb which eventually dries up. This leaves a varnish on the all the insides of the carb and doing this over and over it builds up and with such small openings that is usually what fails.

Edited by Kudzucraft
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54 minutes ago, Kudzucraft said:

We used these, leave them with gas in the carb which eventually dries up. This leaves a varnish on the all the insides of the carb and doing this over and over it builds up and with such small openings that is usually what fails.

Exactly the same with outboard engines - it was even worse with 2-stroke when the petrol evaporated leaving an ever increasing jellified blob of 2T oil in the jets.

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I had a problem with a chainsaw stopping after a few minutes. After several goes at fixing it and nearly giving up I found that the fuel suction pipe was degraded in the tank and had a split. this allowed air to be sucked in. The pipe looked fine between the carb and the tankand teh fault in the tank was not obvious.

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I have a 2-stroke strimmer that worked fine the first season I had it, but ever since it is a real problem to start, will only run part choked (and the setting is really critical - too much open or closed and it stops), and it won't run at full speed. I assume the problem is probably a gummed up carb, although I run it dry after use every time.  I really ought to look into getting either a replacement carb or a service kit.

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In my limited experience of chainsaw and similar (eg petrol strimmers) the gubbins inside the carburettors can degrade and cause problems. We had a troublesome petrol strimmer at the gliding club which was really hard to start, ran badly and gradually got worse until it wouldn’t start at all. There as a good spark so I got a cheapo Chinese copy carburettor overhaul kit (cost a pittance from eBay) and when installed, the thing was transformed and ran perfectly. Which was odd because I couldn’t see anything wrong with the bits I took out. Clearly it was just that the magic juice had ran out. We had a similar problem with the chainsaw but IIRC in the end it turned out to be the ignition coil, even though the old coil was sparking ( a bit).

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4 minutes ago, WotEver said:

Ahhh... the petrol equivalent of magic smoke.  Gotcha.

Yes. It’s exactly the same stuff, just in a different phase (like water vs steam*)


 

 

*yes I know steam is actually liquid water droplets, but “water vapour” sounds too dull.

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36 minutes ago, TheBiscuits said:

 Ahem.  ISN'T ...

Ahem IS SO! Although of course it depends on whether you are a railway anorak or a normal person.
Yes a “steam engine” of course runs by means of steam which is water vapour, as understood by the 1% of the population who enjoy watching trains trundling by because they have nothing better to do with their tedious lives.

But for the other 99% who actually have a life, steam is the thing that comes from the kettle and is of course comprised of water droplets. Ditto for when they failed to ventilate their boats/houses properly, or listen to Tina Turner and get “steamy windows”. 

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13 hours ago, nicknorman said:

Ahem IS SO! Although of course it depends on whether you are a railway anorak or a normal person.
Yes a “steam engine” of course runs by means of steam which is water vapour, as understood by the 1% of the population who enjoy watching trains trundling by because they have nothing better to do with their tedious lives.

But for the other 99% who actually have a life, steam is the thing that comes from the kettle and is of course comprised of water droplets. Ditto for when they failed to ventilate their boats/houses properly, or listen to Tina Turner and get “steamy windows”. 

 

If you can see it, it's not steam, it's water vapour. 

Steam is (a) invisible and (b) at a temperature above 100°C.

 

Unless, or course, my undergraduate thermodynamics course 45 years ago was wrong.

 

A steam engine runs on steam (yes, really) but you can only see water vapour, once the energy has been extracted from the steam. 

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22 minutes ago, Machpoint005 said:

 

If you can see it, it's not steam, it's water vapour. 

Steam is (a) invisible and (b) at a temperature above 100°C.

 

Unless, or course, my undergraduate thermodynamics course 45 years ago was wrong.

 

A steam engine runs on steam (yes, really) but you can only see water vapour, once the energy has been extracted from the steam. 

You are incorrect on two counts. If you can see it, it is not water vapour it is liquid water. Time for a theory refresher, or send back your degree certificate. Secondly, as I alluded to earlier, look up the dictionary definition of steam. It has two meanings. Get over it!

Edited by nicknorman
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