The Accidental Smallholder Forum

Smallholding => Equipment => Topic started by: Nick Benny on March 03, 2014, 08:06:05 am

Title: Chainsaws, What am I doing wrong?
Post by: Nick Benny on March 03, 2014, 08:06:05 am
I am having a rather frustrating time with a pair of chainsaws, one is fairly old and although it works ok, it suffered from a number of 'issues' I managed to iron most of these out and although it won't idle it worked ok for a while and then would lose power and stop even under full throttle.  I then broke the brake band so whilst awiting delivery of a replacment decided that I would buy a new one, because it has to be handy to have a spare!

I bought a McCulloch/Husquarvana, bought new fuel, mixed it with new oil, set up the chain tension and fired it up, awesome for about five minutes, then it loses poser and cuts out, it won't restart for 10 minutes or so then I repeat the cycle, five minutes operation and  then more waiting!

So I have similar symptoms for both chainsaws, what am I doing wrong?
Title: Re: Chainsaws, What am I doing wrong?
Post by: MikeM on March 03, 2014, 08:12:01 am
you are putting the choke back in after it starts? At least, that's one thing that immediately springs to mind.
Title: Re: Chainsaws, What am I doing wrong?
Post by: devonlad on March 03, 2014, 09:05:14 am
I'm wondering about the fuel mix ratio
Title: Re: Chainsaws, What am I doing wrong?
Post by: UPoneacre on March 03, 2014, 10:30:08 am
I've got a fairlry new McCulloch as well, and had similar problems to start with which was partly due to using the wrong fuel mix (note to self - read handbook  ;D). Apart from that the more I've used it the easier it's got so I suspect that everything was a bit tight from new and it needed running in. Can only suggest you check your fuel mix  and then persist.
Title: Re: Chainsaws, What am I doing wrong?
Post by: MikeM on March 03, 2014, 11:09:36 am
just another thought, I also have a mcculoch and cutting out is not totally unusual for chainsaws. McC's have an odd restart/hot start procedure where you have to apply half choke when you crank it. Dunno if it's the same for all their models though.
Title: Re: Chainsaws, What am I doing wrong?
Post by: MAK on March 03, 2014, 01:36:52 pm
I was alerted to a potential problem re: Fuel oil mix. The Stihl oil says to mix to 2% , the Mc Culloch handbook says 3% and the chap servicing all types of chainsaws tells me to use 4-5% with cheaper motor oil.

Any comments re: dirty sparkplug and need to frequent need to clean it - ?
Title: Re: Chainsaws, What am I doing wrong?
Post by: Nick Benny on March 03, 2014, 04:20:54 pm
Yes all these comments seem to fit! I have choke operation sussed, checked plug clean and sparking.
Now fuel mix, the book does say 3%, so 150ml in 5L, ok?
So next bit I guess will be to continue to use and try changing mix to 5%, so 250ml for the 5L, agreed?
Title: Re: Chainsaws, What am I doing wrong?
Post by: Nick Benny on March 03, 2014, 04:21:56 pm
Sorry I forgot to say a big thank you for your help!
Title: Re: Chainsaws, What am I doing wrong?
Post by: spandit on March 03, 2014, 06:28:33 pm
I use the little Stihl oil shots that you add to 5 litres of petrol - seems to work for me
Title: Re: Chainsaws, What am I doing wrong?
Post by: MikeM on March 03, 2014, 06:40:13 pm
I have to say I never scientifically and pedantically measure out the oil/fuel ratio, (though I probably err slightly on the heavy side) and I've never had a problem.
Title: Re: Chainsaws, What am I doing wrong?
Post by: UPoneacre on March 03, 2014, 08:04:20 pm
FWIW I bought myself one of those plastic mixing containers which have the mix ratios marked down the side - just fill up to the first mark with petrol then top up with 2 stroke oil to the required ratio mark - helped this idiot no end in getting it right but I do have to remind myself from time to time that the chainsaw uses a different mix to the hedgecutter to the brushcutter - danged if I can remember which is which at the mo' ;D
Title: Re: Chainsaws, What am I doing wrong?
Post by: little blue on March 03, 2014, 09:29:40 pm
ours is electric, but ... found out the hard way you can't put cheap oil in - knackers it!!

if that's any help!!
Title: Re: Chainsaws, What am I doing wrong?
Post by: rkardo on March 03, 2014, 10:21:04 pm
I have used one Homelite bought by grandfather when i was a kid so  coming to 30 years now with no major issues some parts had to be replaced due to wear and tear but nothing major, I did broke in some of the chainsaws for my uncles they run thru them quite fast due to lack of care and maintenance. 2 things I did one I mixed 5'ish % of used good quality motor oil i got from the mechanic at good price :) second i used duck tape (sellotape) not quite sure how you call it here taped the throttle between 1/4 and half the way in and let it run it into the pace. Just keep an eye on the blade so you notice if oil is dripping...   that shall loose the joints...  :roflanim:
Title: Re: Chainsaws, What am I doing wrong?
Post by: MAK on March 03, 2014, 10:46:54 pm
Nick -150 -250 ml of oil in 5 litres of petrol is correct.
Another tip - If the chain tension drops then you may notice a poor cut and hear the engine working hard - stop cutting as the engine temp will soar and can ruin the engine. Expensive error ! Possibley more likely if you run at 2-3% 2 stroke engine oil.
Title: Re: Chainsaws, What am I doing wrong?
Post by: chrismahon on March 04, 2014, 03:39:32 pm
Sounds like both are seizing up Nick. As all have said, get the oil mix right. Stihl oil is measured at 100mL per 5 Litres of petrol but I always mix it with 4 litres. So that's a 2% mix but some old chainsaws need a 5% mix. I suspect that is because they pre-date fully synthetic oil. If you use too much oil you risk sooting them up.


If the symptoms persist you may need to strip them down and have a look. Friend of mine had a Stihl down on power and discovered the bore all scored up due to seizure.


The chain bar expands during use and can over tighten the chain, in my experience. Not what I expected as I thought both would expand at the same rate, if anything the chain would get hotter and go loose.
Title: Re: Chainsaws, What am I doing wrong?
Post by: Small Farmer on March 08, 2014, 08:25:36 pm
Two stroke motors are very simple and very reliable even when abused terribly so unless it's been run without oil I'd be surprised if that was the problem.   With a modern engine and modern oils I'd stick to the manufacturers spec:  too much oil doesn't actually help combustion because it's just more to be burned and potentially foul the sparking plug.


By far the most common problem is dirty fuel, especially water contamination.  The in-line filters that some modern engines have block easily even from the condensation that you will get inside a partly full can.  Fuel does also go stale if stored even for 12 months: there are some additives but I'm not sure it isn't oil company propaganda.   


Air/fuel mix can be an issue especially if it's too lean when the engine will run very hot.  You can easily check this by cutting into a reasonably sized log.  Off-load the engine should be 4-stroking, making a sort of deep barking noise at full throttle.  On load it should change into a smooth scream.


One other place to look is the air filter.  If the chains aren't kept really sharp sawdust can block the filter and make the engine run badly, though not in 10 minutes.