time to adjust the carb?

[chrismechanic]

ahh, thanks ray, that sounds better than 1 turn out.

im checking the carb for a blockage...

 

whats with all the triangle bolts holding this together, i have never seen that before.

some kind of self locking bolts..

cheers,

chris.

[chrismechanic]

ok, so the carb is clean as can be... looks like new inside, no debris.

reset both needles to 2 and a half turns out, H needle was allready around there.

 

start up, i needed to increase the idle screw to get it to tickover.

 

its badly 4 stroking on tickover now so i assume that is too rich.

but leaving it running and it revs up for a few seconds then cuts out.

 

is that because is it too rich? as i under stood it, thats lean?

like i said, i really dont get this 2 stroke tuning..

cheers,

chris.

[spudulike]

ok, so the carb is clean as can be... looks like new inside, no debris.

reset both needles to 2 and a half turns out, H needle was allready around there.

 

start up, i needed to increase the idle screw to get it to tickover.

 

its badly 4 stroking on tickover now so i assume that is too rich.

but leaving it running and it revs up for a few seconds then cuts out.

 

is that because is it too rich? as i under stood it, thats lean?

like i said, i really dont get this 2 stroke tuning..

cheers,

chris.

 

It is probably just over fuelling, try both H&L screw on 1.5 turns out on each and try again. I think both screws should be 1 turn out. The H screw is the one to make sure you don't lean down too much!

[chrismechanic]

spud,

when i used to tune 2 stroke nitro engines i would use a temp gun to determine the correct needle settings..

 

if the engine where to over heat the barrel would expand more than the piston so they would loose compression and cut out, they had ABC barrels.

will my saw do the same?

 

and any idea what the normal/ideal running temp would be?

 

sorry to bug you.

chris.

[spudulike]

spud,

when i used to tune 2 stroke nitro engines i would use a temp gun to determine the correct needle settings..

 

if the engine where to over heat the barrel would expand more than the piston so they would loose compression and cut out, they had ABC barrels.

will my saw do the same?

 

and any idea what the normal/ideal running temp would be?

 

sorry to bug you.

chris.

 

Right you asked, you set the carb to one turn out on each screw, get it running and set the idle so it is ticking over OK, you then turn the L screw in until the idle speed incteases and starts to falter, you then turn it out past the high point and around 1/4 turn out - the engine goes from an even idle and sounds sort of popity poppy:001_rolleyes:

 

You then rev it a bit and make sure the pickup is good.

 

Then you make sure that at flat out, the saw doesn't over rev, this is normally done with a tach and the manufacturers data or just make sure that the saw sounds a little flubby on the top end - if you don't know how this sounds, turn the screw out 2 turns and then take it in bit by bit until the saw runs cleanly with just a hint of fourstroking (flubbing)!

 

That is how most of us do it - you can do more with timed cuts etc but this method gets us to 95% of where we need to be!

[chrismechanic]

ya, cheers spud.

 

i watched a few tuning vids on youtube and thats pretty much what they said.

basically i need it just lean of 4 stroking on idle with good pickup.

 

so will they loose compression when too hot or would they just seize?

chris

[spudulike]

ya, cheers spud.

 

i watched a few tuning vids on youtube and thats pretty much what they said.

basically i need it just lean of 4 stroking on idle with good pickup.

 

so will they loose compression when too hot or would they just seize?

chris

 

All saws lose some compression when warm just through expansion and thinning of the oil but if it ges too hot through over fast running the piston exhaust side will start to melt and seize.

 

I you have fresh fuel, the carb is correctly adjusted and no air leaks, all should be OK!

[chrismechanic]

i have spent hours on this saw... i can't get it to run right

 

i think i will shoot mcculloch an e mail...this is getting silly, i also notice eveytime i refill with fuel the tank filler screw gets tighter.

i can barely screw the cap back in now after filling, so tight it hurts my pinkys.

 

i just put fresh fuel in today just incase the old fuel had gone off, no change

chris

[doobin]

i think i will shoot mcculloch an e mail...this is getting silly, i also notice eveytime i refill with fuel the tank filler screw gets tighter.

i can barely screw the cap back in now after filling, so tight it hurts my pinkys.

chris

 

Good luck with that.... all you'll get back is a list of 'authorised service centres'!

 

I feel your frustration- knowing you should be able to fix it but it won't play ball. Honest advice? If you need a saw, skip the McCulloch and buy a small Stihl or Husky.

[Welshwoodsman]

Good luck with that.... all you'll get back is a list of 'authorised service centres'!

 

 

 

I feel your frustration- knowing you should be able to fix it but it won't play ball. Honest advice? If you need a saw, skip the McCulloch and buy a small Stihl or Husky.

 

 

Sounds like my virually brand new MS291- only brought is as i thought i had killed my ms250- but a good tube of chemical metal fixed the hole in the body that was letting the oil pump suck in air- so 291 has sat with only 2 hours use in the container in yard since april. Went to use it, fresh fuel- wont run. Will start on choke, and actually run- but once revved, dies instantly. After a bit of faff with it- come to the conclusion that new saws are crap, the old neglected battered abused 250 always starts- but i just ripped the rear handle clean off it- hence wanting to ply the 291 into service- so persevere, tale back to dealer, or chuck it in the canal?

 

 

Sent by smoke signal from my teepee.