Tuning a chainsaw - need help
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From: Wyoming
Tuning a chainsaw - need help
Got my OLD McCoullogh Eager Beaver 2.3 running - finally. It was unused for about 7 years, and after taking the carb apart and hosing it down with carb cleaner it is now running. A new spark plug and fuel filter probably helped.
It has 2 carb screws - labeled H and L (assume that is high and low). The manual is long gone (bought this thing in '92). How does one tune with the two screws? Right now it seems to run best with the choke covering about 1/3 of the carb throat - that can't be right. I'm running it at about 6000 ft elevation; I would think it would be almost starving for air. It's got a marginal idle for now too.
One more concern - I've been adding some injector/carb cleaner to the gas. Will this screw up the lubrication of the 2 cycle? I figure it would be okay short term.
It has 2 carb screws - labeled H and L (assume that is high and low). The manual is long gone (bought this thing in '92). How does one tune with the two screws? Right now it seems to run best with the choke covering about 1/3 of the carb throat - that can't be right. I'm running it at about 6000 ft elevation; I would think it would be almost starving for air. It's got a marginal idle for now too.
One more concern - I've been adding some injector/carb cleaner to the gas. Will this screw up the lubrication of the 2 cycle? I figure it would be okay short term.
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From: So Cal
My manual is at home, probably packed somewhere, but foggy memory is that one screw is for idle mixture. Tune it until the engine starts to speed up and then back off a bit.
The second screw is for throttle transistion, ie squeeing the throttle. Tune it so that when you squeeze the trigger the engine transitions smoothly from idle to full speed ahead. If it is tuned wrong the engine will stumble and maybe die. I think if it is tune too much the other way it runs rich and bogs.
Good Luck,
Jim Henderson
The second screw is for throttle transistion, ie squeeing the throttle. Tune it so that when you squeeze the trigger the engine transitions smoothly from idle to full speed ahead. If it is tuned wrong the engine will stumble and maybe die. I think if it is tune too much the other way it runs rich and bogs.
Good Luck,
Jim Henderson
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You need to depress the trigger to full throttle to adjust the H screw for best operation.
The McCulloch site should have a PDF file of a manual.
http://manuals.mtdproducts.com/mtd/public/list.jsp
If not I'll scan mine for you.
The McCulloch site should have a PDF file of a manual.
http://manuals.mtdproducts.com/mtd/public/list.jsp
If not I'll scan mine for you.
Last edited by Mil1ion; Apr 30, 2007 at 05:16 PM.
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From: Lancaster County PA
Although i don't do a great deal of major 2 cycle work, I have tuned quite a few over the years.
I have had excellent results fattening the mixture at high speed so you get a little "4 cycling". In other words, don't lean it out until it screams like a banshee. When the engine is under load, that lean mixture is going to raise temps. Open it wide up, dial in the high speed needle until it sounds like a "perfect" tune, then open that HS needle slightly until you get an occasional "brraaap" while at full throttle.
That's just the way I do it. I think I learned it at a Stihl tech update meeting I attended.
I have had excellent results fattening the mixture at high speed so you get a little "4 cycling". In other words, don't lean it out until it screams like a banshee. When the engine is under load, that lean mixture is going to raise temps. Open it wide up, dial in the high speed needle until it sounds like a "perfect" tune, then open that HS needle slightly until you get an occasional "brraaap" while at full throttle.
That's just the way I do it. I think I learned it at a Stihl tech update meeting I attended.
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Joined: Jul 2006
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From: Las Vegas, NV
ckal704 has it right. If you tune it until it screams, you will most likely burn up the engine. Keep in mind that you should tune the high needle first, then set the low or idle needle. You will need to re-set the high needle again after the low is set.
I have always set my high needle until it was screaming then backed off a 1/4 or 1/2 turn. I used to do a lot of log cutting years ago when I was building log houses, and selling firewood as a side job. I had both McCullough, and a Stihl 44 that ran for years. Man that stihl was almost scary when it got wound up and cuttin".
I have always set my high needle until it was screaming then backed off a 1/4 or 1/2 turn. I used to do a lot of log cutting years ago when I was building log houses, and selling firewood as a side job. I had both McCullough, and a Stihl 44 that ran for years. Man that stihl was almost scary when it got wound up and cuttin".
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From: Blue Hill Township
Its amazing what a little carb work will do for small engines.
We have a small snowblower at the shop for the sidewalks in the winter. One of the guys that works for us attempted to tune it last winter or something like that but the dang thing wouldn't run right unless it was half choked and you could not throw snow and drive the wheels at the same time. I got sick of it this winter and grabbed my screwdriver and got her runnin like a champ. Everyone was so suprised that the little snow blower ran that good.
We have a small snowblower at the shop for the sidewalks in the winter. One of the guys that works for us attempted to tune it last winter or something like that but the dang thing wouldn't run right unless it was half choked and you could not throw snow and drive the wheels at the same time. I got sick of it this winter and grabbed my screwdriver and got her runnin like a champ. Everyone was so suprised that the little snow blower ran that good.
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Originally Posted by smokestone52
ckal704 has it right. If you tune it until it screams, you will most likely burn up the engine. Keep in mind that you should tune the high needle first, then set the low or idle needle. You will need to re-set the high needle again after the low is set.
I have always set my high needle until it was screaming then backed off a 1/4 or 1/2 turn. I used to do a lot of log cutting years ago when I was building log houses, and selling firewood as a side job. I had both McCullough, and a Stihl 44 that ran for years. Man that stihl was almost scary when it got wound up and cuttin".
I have always set my high needle until it was screaming then backed off a 1/4 or 1/2 turn. I used to do a lot of log cutting years ago when I was building log houses, and selling firewood as a side job. I had both McCullough, and a Stihl 44 that ran for years. Man that stihl was almost scary when it got wound up and cuttin".
Is this a one man job, or does it take another hand to hold the saw's top handle? If I keep my right hand working the throttle, the saw's going to want to vibrate around quite a bit.
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From: Wyoming
Left the chain on, put it in a vise, and got it tuned pretty good. The High screw was good at about 1.25 turns - rpms topped out at 1.0 turns. but the Low went all the way to about 2.5 turns before things began to smooth out. It must have a little blockage left in the carb. I started at 1.5 turns with both. Stunk up the garage for awhile since that's where my vise is mounted.
Seems to be good as new now. I'll try it out soon on some ponderosa pine. Thanks for the help.
Seems to be good as new now. I'll try it out soon on some ponderosa pine. Thanks for the help.
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