Anyone know owt about chainsaws?

[biodoctor]

no needles - it's one of those carbs with a diaphragm rather than needles.

is there a split in the diaphram ?,ive heard that the diaphrams can also stretch and go floppy so it moves but wont pull/push any fuel .

 

[breezer]

Already changed the diaphragm. That was 1st thought. I was still quite upbeat at that point

As regards the wisdom of my old man - yeah he's old & wise enough to think - I've not got the time to **** about with the bloody thing - he just asks me to!

Oh for the experience of age and the energy of youth!

 

[Sam]

Checked exhaust, checked settings, fresh petrol, nothing doing...

no idea what is wrong with it! It's got me stumped.

Cheers for the ideas though fellas!

For both machines to develop the same problem at the same time I would still be inclined to try new fuel and mix!

 

[tigler]

If the spark is definitely ok , timing is correct it has to the fuel system unless it's losing compression when hot.

 

[pedrobedro]

Will it try to run with some fuel down the plughole ? If you've done anything to the carb it may need the settings altering now. Does it have two screws like mine, one for mixture and one for tickover ? Screw the mixture screw in counting the turns then back out again to the same place and a bit further out or in a little at a time. It can't hurt to experiment with it if it gets some reaction. When mine is cold and been stood for a while I have to give it a good shake to get it to fire but it never needs full choke, more like half to three quarter with the half throttle stop clicked on.

 

[Omniata]

Make a slightly oil rich fuel/oil mixture... If it normally has 50:1 use 40:1, if it's not been used for ages, 35:1...

Sounds like it's seizing if you getting part of a run...

If it has full choke crank it until it "barks". Squirt a drop of "easy start" inside the air filter, then instead of knocking to half choke go straight to no choke and pull as hard and fast as you can...

Rev up to full throttle, if it hits a good solid rev on full throttle gently back it off to idle...
Should just tick, if it doesn't, just up the low idle a tiny bit, 1/8th of a turn...

Try to avoid fiddling with the high speed screw unless you absolutely have to...


Avoid pouring neat oil in the cylinder, it won't really help the saw or your lungs

Edit: If the saws not been properly used for a while I'd run it on the slightly rich side...
If the spark plugs "biscuit brown" it's set fine, black = too rich, white = too lean... Grey is not the happy medium

 

[breezer]

IT'S SORTED!!!!!

The link madkayaker put up was to a different parts catalogue than the one I have. It turns out the spark arrestor screen was not what I thought it was. I took the exhaust apart, cleaned the spark arrestor screen and it was off like billy-o.

It's got 3 screws a tickover screw, plus (I think) high & low mixture screws. One red one blue, these only have about 270 degrees adjustment.

The plugs a bit on the black side, but this MAY just be down to the fact I could only get it running with the choke on. I'll try a new plug & see where that takes us.

I've had to wind the tickover screw out a bit further than the manual states, but it starts, ticks over, revs up & holds revs now, so I'm hoping it's okay.

As my old man thought it was dead he's well pleased - anything he gets out of it now is a bonus.

Thanks for ALL your help & thoughts & ideas.

 

[shenion]

Good to hear. Those mixture screws I referred to before. They should be marked H and L (L is usually closer to the engine.)

I adjust the high at full throttle out until it starts 4-cycling (pitch dropping down an octave.) Then in 'till it just barely runs smooth.

Worked a lot on those carbs for my R/C planes. Those plastic caps that limit the adjustment screws seem to accidentally break off

 

[Justme]

Does it have two screws like mine, one for mixture and one for tickover ?

Most chainsaws have a H & L screw.

They are for setting the mixture / max & min revs at tickover & full throttle.

H= high speed screw
L = low speed screw

 

[scotclayshooter]

Most chainsaws have a H & L screw.

They are for setting the mixture / max & min revs at tickover & full throttle.

H= high speed screw
L = low speed screw

Yep and its best to set the L first as the L affects the H setting a fair bit

http://www.madsens1.com/saw carb tune.htm

Theres a WAV file on the page. The secret is to listen through headphones and you will hear what your looking for better.

As for reading the plug you really need to be cutting at full throttle and just hit the kill switch then pop the plug out as even returning to idle can change the colour of the plug.

Making saws faster is a hobby of mine

 

[scotclayshooter]

http://www.youtube.com/watch?v=3UTDBQ-N82o

Some proof i know a little bout saws LOL

 

[Sam]

My mate who owned Swona performance exhausts was hydroforming expansion exhausts for competition cutting chainsaws. Only saw (no pun) it on tv once was Robby Coltrane on one of his journeys stopped off at an event. Mad!

 

[scotclayshooter]

My mate who owned Swona performance exhausts was hydroforming expansion exhausts for competition cutting chainsaws. Only saw (no pun) it on tv once was Robby Coltrane on one of his journeys stopped off at an event. Mad!

Theres vids on youtube of hydroforming with just a pressure washer!

If i had more time i would make up a "pipe" but to be good on a pipe the port timing has to be radically altered.

Ive started using flat special shaped files on the chain and there seems to be amazing gains over round filed it slices the chips out rather than rippeng them out but the edge is less durable and the sharpening takes longer.