OT: chainsaw question

Most don't spark until over 400rpm, often the clutch dragging will prevent pulling it over fast enough.

Whip the exhaust off and check the rings are free through the exhaust port.

AJH

I often have to get similar things going for the allotment holders nearby, most common are fuel problems rather than spark, such as fuel lines that have gone rigid or cracked. The other common fault is that people leave fuel in the machine and leave it for six months, meaning that the mix on a two stroke becomes very oil rich, and it may also gum in the jets, restricting their size, making it run weak (which sounds like your problem from here.) Have you checked the spark with a new plug? Your plug may be sparking internally. That leads to another problem, people using ordinary engine oil instead of two stroke oil and adding a little extra oil to the mix, which makes it run weak and overoils, and clogs up the plug, which is then pretty much useless due to the deposits on it, it also clogs the rings and the exhaust. The other common problem is leaking crankshaft seals, which draw in air, making it too weak to start, particularly from cold, again a distinct possibility in your case.

Mrcheerful wrote: [snip]

In general, once I have it running, as it runs out of fuel it goes faster - which suggests to me that it normally runs rich.

But it has been left over the summer with fuel in it, so I might drain the tank and wash it out with neat petrol before refilling with the correct mixture.

Do you have any recommendation for cleaning jets in situ rather than dismantling the carb?

You could try a tiny bit of car fuel system cleaner. The stuff that will definitely dissolve fuel residue gum is nitrocellulose thinners. But in one extreme case I actually had to resize a jet using a one of the tiniest drill bits, about a size 72 iirc because the gumming was so bad where it had been left for a couple of years with fuel in and the fuel tap on.

[...]

All petroil two-strokes do that.

Chris

and more ....

Clamped it to a workbench so I could pull the starter with both hands. After many pulls it started, but would not run at full throttle - suggests not enough fuel getting through. I kept it going for a couple of minutes until it was properly warmed up then let it tick over - which it did happily for another minute or two. It then died, and would not start despite several more pulls.

Took out plug - clean and dry - so probably no fuel getting through. Next step is to dismantle and clean the carb. U-tube has a good video. Though no explanation of how fuel is pulled into the carb - can anybody point me to a website which explains how these carbs work, please?

Related question:

My sister and her husband have an Efco MT440 chainsaw bought in 2012. Husband used it successfully until last and winter.

Husband now slowly dying of lung cancer, so no longer strong enough to pull the starter. So my sister wants to use it. She paid the local dealer to service it, and saw it running in their workshop when she collected it. But she is just not strong enough to pull the starter successfully.

Is there any clamping mechanism available that would allow her to stand and use both hands to pull the starter? Ideally something that she could take to where she is collecting the firewood?

Alternatively does anybody know of a model with a foot-operated starter?

TIA

Pumps are usually operated by engine suction, on the carb there will be a sort of square bit with a rounded middle, inside there will be a rubber diaphragm with two little ears which act as one way valves, plus a light spring. Sticking or obstruction of the ears is possible as is a hole in the main diaphragm. One of my chainsaws died because the fuel pipe inside the tank had cracked, another refused to work unless it was on its side as the fuel pipe had become stiff, which meant that the weighted fuel pick up could not fall into the petrol, both would run with a full tank of fuel for a while.

There are several makes of electric start chainsaws (macculloch and stihl at least).

My recommendation would be to move her to an all electric chainsaw and get an inverter to run it remotely (but near a car) Electric chainsaws are a revelation after petrol ones.

or get her a battery powered chainsaw, depending on her needs it might be more than adequate.

Does she know what she's doing with it...?

Put it on the ground, foot on the wider bit of the handle, and both hands on the cord. Will that give her enough leverage?

If not, is she up to manhandling the uncut logs about...?

I have an old B&D cordless and it is remarkably effective even with NiCad batteries which I wouldn't normally use these days.

[snip]

That's worth a try ...

I had one a long time ago - about 1kW rating - was OK for small logs - up to about 3-inch diameter.

But even then, 1kVA from a car battery via an invertor is a significant problem - would need about 80A continuous at 12v - don't think many alternators are up to that.

But this is for serious firewood - fallen trees up to a foot thick ...

I've tried this with mine - I still need one hand on the front handle to stop it twisting up as I pull ...

- er no, and neither would I be. Mainly fallen trees in local woodland. Generally have to cut into 1-foot lengths to lift into trailer - then split once brought home.

[...]

It wouldn't be continuous though. The maximum current would only be when actually cutting; perhaps 50% of the time?

Even modest cars have 80A alternators nowadays. It's about the lowest rating available, and 125A is not uncommon. As long as the battery was in good condition you would have some reserve.

Chris

[snip]>>

I've looked at both those manufaturers' websites. There are battery powered chainsaws, and petrol.

The battery powered models don't have a petrol engine - they rely toally on the battery.

All the petrol versions have "recoil starters" which means that the starter rope "recoils" into the housing when released.

NONE have a battery to turn a starter motor - which is what I would like to obtain.

Can you state a model number for one with true "electric start", please?

TIA

Looks as though they are no longer available here.

mcculloch 310 e, but they no longer make them, stihl apparently also made an electric start model for a short while (unknown number)

stilh now make ergo start chainsaws, two finger gentle pull and away , which works by interposing a clock spring between your pull and the crank, so you do not get the compression to overcome directly with your arm

Strange! My lawn mower is electric start - and the battery is about a

6cm cube. I see that even something that small would be a problem with a chainsaw, but surely a 12v motor and a cable to a car battery would be practical. See

- towards the end of the video you can see the separate battery, or - separate 12v motor with friction coupling ... I'm sure I remember model aicraft engines (in about 1965) with a "spring start". You wound the prop slowly the wrong way against a spring, energised the glow plug then released the prop. The spring turned the prop the correct way - really fast - and the engine would fire. I always undestood that to be the definition of "recoil" ... I'm sure the same technique could be made to work with a chainsaw.

But you had to get your fingers out of the way fast! I'm shuddering at the idea applied to a chainsaw.

;-)

It's certainly been done with lawnmowers. They had a crank on the top that you used to wind up a spring. Not sure whether it ever really caught on in a big way though. (A quick search on't web suggests that they were more trouble than they were worth).

Tim

[...]

The other big problem with any sort of self-starting system applied to a chainsaw is weight; if you're using one all day, and perhaps climbing trees with it hanging from a belt, every gram counts against you.

Chris