The L mixture is not for the purpose of setting the idle speed, although it affects it. It's sole purpose is for setting the fuel/air mixture at idle. It is the purpose of the LA screw to set the idle speed AFTER the L needle has been properly set.
Have I been tuning saws wrong
- Thread starter mopar969
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This is how I tune a saw, starting with the L needle. In this case there was no need to change the idle speed after setting the L and H mixture needles.
jmssaws
Addicted to ArboristSite
Yep that's the way I do it.
Very rarely do I need to adjust the la.
I guess on a stock saw that I was trying to get to 2500 exactly the la is handy but all I tune is ported and not to a rpm just to power and the chain not coasting.
Usually a little faster than spec.
Like 27 to 2900 is where they idle.
Some will go slower but not all.
Depends on the carb
jmssaws
Addicted to ArboristSite
When you go to tune one where do you set the la?
I think that 1.5 turn from the point where the screw just start to touch the butterfly is good.Every screw on the carb is highly related with the others.L screw can affect idle as blsnelling said such as a lean H screw can affect acceleration.But every screw has its point and must be used only for its propose.I am not saying that you are doing something wrong,i am far from expert.
M
MattG
Guest
Not quite. The influence of L and H screw will overlap in the middle of the airflow to an extent i.e. at certain points in the airflow the FA mix will have a contribution from both.
D
Deleted member 135597
Guest
What would a really lean tune rpm be for a stock ms461 (well it does have a dual port muffler cover) ?
Amp4027
ArboristSite Operative
So if a technical manual says that the default setting is 1L and 1 1/2H out from lightly seated, and the limiter caps should be set at 1/4L and 3/4H - does that mean that the actual adjustable setting (in relation to lightly seated needles) of the carb screws is 3/4 to 1 1/2L side, and 1 to 1 3/4H?
Big_Wood
westcoast dweller
who's the goof in the video? i was gonna say he didn't know how to tune but then saw he knew he was making it unusable so that ok then lol
jmssaws
Addicted to ArboristSite
Tuned 2 saws today.
A 395xp and a 044 that I ported today.
The 395 is Shaun's that he sent me to play with and run against this 394 I did a week or two ago,I start it to check the tune and it was pretty much dead on,surprising seeing how he lives in another state.
To me a 395 always sounds lean at idle,almost sound like a lean surge
A 395xp and a 044 that I ported today.
The 395 is Shaun's that he sent me to play with and run against this 394 I did a week or two ago,I start it to check the tune and it was pretty much dead on,surprising seeing how he lives in another state.
To me a 395 always sounds lean at idle,almost sound like a lean surge
M
MattG
Guest
Approximately, yes... I've removed caps from several STIHL power tools, and sometimes been able to leave the screws "where they were" for comparision. And yes, you notice the incrementing effect of the initial setting. I don't agonise on it a great deal, as you get some variance in the how the limiter cap tabs bear up against lugs on the carby... and also you tend to see a bit of variation with "not perfectly fitting" screwdrivers in the screws slots.
So I tend to ignore these "fractional settings e.g. 1 1/2" and use my ear or a tach or whatever.
Amp4027
ArboristSite Operative
So if you are basically 10ft above sea level, and its 70-90degs out on average (Florida), where exactly would it be approximately when compared to a saw tuned for somewhere like Colorado (1 mile above sea and much much colder air)? If the saw was tuned perfect here, and went up to there, would it be too lean without changing the carb settings, and have to be made fatter?
Chris-PA
Where the Wild Things Are
You seem to be hoping to get someone to tell you how many turns the screws should end up for various conditions, but this isn't possible. The carbs just are not accurate enough for that and initial settings of X-turns are just that - a starting point to get it going before tuning. There isn't any way around actually tuning the saw.
When you go up in altitude the air pressure is lower and air molecules get farther apart, therefore each intake stroke pulls in less oxygen and the mixture will be too rich. So at higher altitude you must lean the mixture.
Amp4027
ArboristSite Operative
This is what I was looking for - Perfect. Thanks!
Gypo Logger
Timber Baron
A saw ran rich most of its life will be carboned up, so leaning it to specs can cause piston score on the exhaust side. Plus a saw won't tune if the spark arrestor is clogged.
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