tuning a saw?

[billpierce]

can anyone point me to some reliable advice and instructions of tuning a carb? have fiddled with various saws over the years when they seem crap and all seem to run sweet but don't want to end up damaging them.

 

thanks in advance

[predator]

spuds your man he will put it plain and simple

 

meanwhile lol screw the h & l screw in gently till they stop then unscrew one full turn anti clockwise then start the saw up n warm it up etc then give it a quick rev to see if its got any flat spots if it has try unscrewing the l screw out 1/4 turn then try it again if it's ok then try the saw flat out clear its throat so to speak and if it screems you need to un screw the h screw 1/4 turn at a time untill it sounds like its burbling at peak rev's do not run the saw flat out for more than you need to whilst tuning the carb but make sure its burbles or whats call four stroking before you put the saw to any work as it will bugger the engine i think thats about it just tweek the screws till its got no flat spots and burbles at peak revs then set the idle screw so you dont get chain creep

[wyk]

Mitch has got it goin on:

 

[billpierce]

Thanks - when you say 4 stroking/ burbling i assume you mean not screaming, but not sort of bogging down (prob the wrong way of describing it) - its seems too rich on H and it starts to drop a bit so just off that yeah?

 

white spark plug = too lean?

 

chocolate spark =about right?

 

black = too wet?

 

does this forum have sticky threads? i had a bit look for tuning a carb on here but i think that phrase bought up far to many threads mentioning tuning.

 

thanks again for the help!

[spudulike]

Thanks - when you say 4 stroking/ burbling i assume you mean not screaming, but not sort of bogging down (prob the wrong way of describing it) - its seems too rich on H and it starts to drop a bit so just off that yeah?

 

white spark plug = too lean?

 

chocolate spark =about right?

 

black = too wet?

 

does this forum have sticky threads? i had a bit look for tuning a carb on here but i think that phrase bought up far to many threads mentioning tuning.

 

thanks again for the help!

 

Four stroking on two strokes means the carb throwing in so much fuel in to the engine at flat out revs that every other spark fails to ignite the fuel hence the term.

 

In real terms, you are using the H screw of the carb as a rev limiter - tune it too lean, the saw will over rev and get so hot, the piston will melt on the exhaust side as it is the hottest.

 

The four-stroking phenomena sounds like a reverberating or drumming in the exhaust note at flat out revs, on some very high revving saws, it is almost impossible to hear but the spark plug colour will be a good guide.

 

If you are unsure about this, set the H screw to 2 turns out and see how strangled the machine sounds when revved turn it in to 1 1/2 turns and hear it clean up and then at 1 turn, there will just be a slight hint of fourstoking.

 

A tach is a useful tool in getting a saw up to optimal safe top speed running as you set the carb so the machine will rev up to a set maximum RPM set by the manufacturer.

 

Easy:lol:

[billpierce]

great. thats pretty much what i've been doing but real nice to know your not definately wrecking your saws.

 

what tach would you use? i seem to like running really old saws bought cheap then uneconomically spending loads of time and money fixing them constantly - learning to tune good must be pretty key to al this - and reckon many saws are scrapped as they are out of tune?

 

thanks again

[spudulike]

great. thats pretty much what i've been doing but real nice to know your not definately wrecking your saws.

 

what tach would you use? i seem to like running really old saws bought cheap then uneconomically spending loads of time and money fixing them constantly - learning to tune good must be pretty key to al this - and reckon many saws are scrapped as they are out of tune?

 

thanks again

 

I use a Tech Tach TT20k, the good part is that it is induction based and needs no wires to attach to the engine, it also has a replaceable PP3 9v battery.

 

Cost is around £75 and worth every penny as I have tuned hundreds of saws with it. The UK rep (Richard) is a decent fellow and they actually send out the kit without payment and then trust you to pay on receipt - very trusting and great service.

 

If you choose another, make sure it is capable of reading to over 15,000rpm and also has a 0.5 second refresh rate as you don't want to be revving that engine flat out for longer than is needed. I do recommend what I have mentioned above though!

[billpierce]

so i was trying to sort out a 254xp (doesn't get much better!) today for a pal, he said it kept cutting out. all seemed good, so had go at tuning. got it running sweet except that it would occaisonally stop if say you were starting a cut, a tooth caught on the wood so the chain wouldn't move, normally you would just release the throttle a bit and lift the saw but as soon as you released the throttle it would stop. no biggy but just wandered what i might have done wrong?

 

also it would occaisonally stop if you were leaning into a cut and took your finger off i.e revs going from high to low quickly - maybe normal?

 

thankyou thankyou thankyou in advance

[mikerecike]

Could be idle speed set a bit low. You can take it up to just below point of clutch engagement.

 

Sent from my SM-N9005 using Arbtalk mobile app

[billpierce]

Thanks mikerecike - its about as far as it can go without chain creep. it seems to help if you wack it up a bit but then you get a decent bit of chain creep which i reckon is worse!