Quick question: Is it true that a chainsaw should always be run at WOT when cutting? Just curious, since I will often use less than full throttle to give myself better saw control, esp. in tricky cut situations.:greenchainsaw:
Wot?
- Thread starter teacherman
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gink595
Addicted to ArboristSite
Thats what I always assumed, I thought that the carbs didn't have a way of metering part throttle use ie. needle jets and such. I thought they were tuned for running wide open. I normaly run my wide open, but feather out the throttle near the end of the cut.
Jonsered2095
ArboristSite Guru
Good question!
Re-phrased:
Does the vacuum caused by the shape of the barrel (Venturi) mysteriously disappear between idle (low speed jet) and WOT (high speed jet) or just the flow rate decelerate/accelerate?
What would cause any reduced flow through the venturi to off-set optimal tuning set at WOT and idle?
And should engines with two barrel+ carb.s on motor cars only be run at WOT also?
Re-phrased:
Does the vacuum caused by the shape of the barrel (Venturi) mysteriously disappear between idle (low speed jet) and WOT (high speed jet) or just the flow rate decelerate/accelerate?
What would cause any reduced flow through the venturi to off-set optimal tuning set at WOT and idle?
And should engines with two barrel+ carb.s on motor cars only be run at WOT also?
gink595
Addicted to ArboristSite
1) No, it has to be there, that is what causes more or less fuel to be metered.
2) I'm not quite following your question, but there is several stages to metering fuel throughout the rpm range, idle, part throttle/cruising adj. by needle jets, WOT main jets. there are all kinds of different carbs that work numerous ways, but all have a specific use, obviously you can't run a car wide open, like a chainsaw. As far as I know a chainsaw doesn't have a part throttle adj. therfore it can be run at an idle and WOT. That is why you have to tach tune at a specific rpm.
Bowtie
Gearhead
opcorn:
gink595
Addicted to ArboristSite
For arguments sake, This explains the chainsaw carbuerator's functions.
http://auto.howstuffworks.com/question377.htm/printable
http://auto.howstuffworks.com/question377.htm/printable
ropensaddle
Feel Lucky
Bowtie
Gearhead
Well what ya think teacherman? Is wot the best way to cut? You convinced or not?
Bowtie
Gearhead
I run my saws WFO........:greenchainsaw:
Me 2
stihl 440
Addicted to ArboristSite
chainsaw
If you run a saw at mid-throttle it will cause it to produce carbon build up on the P&C, and eventually it will lean the carb out and the saw will not run right. I had buddies that did this and would not listen to me, and they eventually fried their saw running it mid-throttle. They learned....but the hard way. They run em' wide open now and no porblems.:greenchainsaw:
If you run a saw at mid-throttle it will cause it to produce carbon build up on the P&C, and eventually it will lean the carb out and the saw will not run right. I had buddies that did this and would not listen to me, and they eventually fried their saw running it mid-throttle. They learned....but the hard way. They run em' wide open now and no porblems.:greenchainsaw:
Last edited:
grandpatractor
Addicted to ArboristSite
I run my saws WFO........:greenchainsaw:
Me 3
Bowtie
Gearhead
POST 2000! And I did it running my chainsaw at WOT!!!!!
:greenchainsaw:
:greenchainsaw:
gink595
Addicted to ArboristSite
POST 2000! And I did it running my chainsaw at WOT!!!!!
WoooooooHooooooooo
Congrats, finally fluffed your way to 2K. HaHa
Freakingstang
Doctor Freakinstein
WOT or nothing.
There is not part throttle fuel metering on these simple carbs, if there was there would be a 3 mixture screws.
on a conventional saw carb, There are three screws, but only two adjust fuel flow. There is a low jet mixture screw that controls fuel metering at idle speeds. The high jet mixture screw controls the amount of fuel that is metered at WFO.
The idle screw has nothing to do with fuel. It adjusts the throttle shaft to let more/less air through the carb body/ There is no fuel adjustment with that idle screw, only mechanical shaft positioning.
There is not part throttle fuel metering on these simple carbs, if there was there would be a 3 mixture screws.
on a conventional saw carb, There are three screws, but only two adjust fuel flow. There is a low jet mixture screw that controls fuel metering at idle speeds. The high jet mixture screw controls the amount of fuel that is metered at WFO.
The idle screw has nothing to do with fuel. It adjusts the throttle shaft to let more/less air through the carb body/ There is no fuel adjustment with that idle screw, only mechanical shaft positioning.
JLROOT
ArboristSite Operative
I am not a carb man but my manual says to use WOT. Then again it also says some other stuff that I choose to ignore.
rms61moparman
Addicted to ArboristSite
I am not smart enough to enter into the carburetor issue but the old gentleman that taught me to run chainsaws always said that part throttle cutting allowed the clutch to slip too much creating all kinds of heat/clutch issues.
Mike
Mike
Freakingstang
Doctor Freakinstein
I have heard the same, but have no proof that it actually does...
WOT for normal cutting. Partial throttle for those finesse situations will be fine. Just dont go with partial for regular long cutting .
Freakingstang
Doctor Freakinstein
yup.
Every now and again when I finish a cut on the ground, I let it idle down so I don't hit the dirt at WFO
