Carb tuning

Bermy

Bermy

Acolyte of the short bar
Joined
May 3, 2008
Messages
8,626
Location
Tasmania
I have about six tanks run through my new 461 now, but full in a cut it doesn't lose what I think is called that '4 stroke' sound, it still sounds like a bit of a double beat. Will you only get the crisp sound at full throttle when cutting wood, will it still '4 stroke' if you are not using full throttle when cutting?
I can do the basic tuning on saws but am in no way approaching the level of skill and experience of some of you guys...

I ran the video of Randy and the 150 and it was very obvious how it went from the '4 stroke' to a clean crisp sound...
I think I got it right on my other saws by chance!
 
Fiona, you should be getting a bit of four stroke at full throttle. Is it four stroking at lesser throttle? Good technical question, I suspect it is more so, but you can't really decipher it from the total sound. I could be wrong. At max rpm there should still be a bit of warble in the noise. Not having that is risking damage.

Running at full throttle most all the time when cutting, including small stuff, it seems to be one of the most common misuses of chainsaws, a bad habit that almost everyone has, including myself. Tons of gas gets used up that way when it doesn't really need to be. A guy keeps telling me that. :lol:
 
I'd recommend tuning the 461 with a Tachometer. The 461 has a rev limited ignition system to keep the engine from spinning faster than 13,500 RPMs. When they ''hit'' the limiter it gives about the same sound as fourstroking does. Easily mistakable. You can also tune it in the cut by starting rich at first, then lean it out a little at a time while cutting until you think it's right. Both ways work well, but if your not comfortable tuning it in the cut, I recommend a tachometer.
On saws without a rev limited ignition tuning by ear works excellent.
 
Full throttle all the time when making small cuts leads to bottom end failure prematurely also.
 
komatsuvarna said:
I'd recommend tuning the 461 with a Tachometer. The 461 has a rev limited ignition system to keep the engine from spinning faster than 13,500 RPMs. When they ''hit'' the limiter it gives about the same sound as fourstroking does. Easily mistakable. You can also tune it in the cut by starting rich at first, then lean it out a little at a time while cutting until you think it's right. Both ways work well, but if your not comfortable tuning it in the cut, I recommend a tachometer.
On saws without a rev limited ignition tuning by ear works excellent.
Click to expand...

I'd listen to Durand.....he knows saws.
 
Tuning a saw in the cut seems like there could easily be the tendency to make it too lean, like when then going WOT not cutting. That would take getting familiar with the method, it seems, otherwise risky.
 
You make the saw too fat. Then lean it out a little at a time, making sure it still four-strokes when you lift pressure in the cut.
 
When using a digital tach should the high end be tuned while running WOT with no load?
 
That is my understanding, Leon. One thing I find though, and i think I have a good tach that refreshes quickly, is the rpms really jump around when taking readings, varying as much as three or four hundred rpms when WOT. Sometimes the number will stick for awhile at one particular, but then it will start jumping around again. When it stops at one number for a bit, i usually see that as the best reading, but even with a tach, i think it takes a bit of feeling it out with the sound.
I've often wondered if the rpms are really jumping around like that, or that is just how the tach reads for some reason. A tach with a memory for highest rpm is helpful.
 
Thanks Jay. My experience with my digital tach (got it from Bailey's) is similar. I've got to work on hearing the right sound.
 
  • Thread Starter Thread Starter
  • #14
Thanks guys...I run my saws at the throttle that is appropriate for the work they are doing.
Usually I set them factory spec then twiddle a bit, listening to them...(the description I have on the page from my workshop notes from school are pretty good) then check the plug colour after a couple days work. I'm always very careful not to set them too lean.
High jet tuning is the one I find trickier than low, what with the sound level!
 
To many it seems almost counterproductive to have a saw blubbering away running slightly rich .However once you get slightly into the cut that excess fuel turns into power .

There's a gent from Ohio I won't mention his name that did a pretty fair job of souping up a saw but always ran them too lean .They simpley would not cut what their potential was .He got it because the last several times we've met those saws run a whole lot better than before .
 
I had a hard time being real happy with the tune of my 461 till i swapped out the 460 coil ,in small stuff it bounced off the rev limiter a lot with the stock coil making it harder to tune ,i am real happy with the saw since i swapped coils
 
Al Smith said:
To many it seems almost counterproductive to have a saw blubbering away running slightly rich .However once you get slightly into the cut that excess fuel turns into power .

There's a gent from Ohio I won't mention his name that did a pretty fair job of souping up a saw but always ran them too lean .They simpley would not cut what their potential was .He got it because the last several times we've met those saws run a whole lot better than before .
Click to expand...

That helped......but me pushing him helped even more Al. I drove him like a borrowed mule till he got a lathe, and some right angle tools.

Brad and I have ended up becoming pretty good friends.....
 
Many of the tach's are too slow to respond and the rev-limiting coils may further confuse them, but definitely use a tach to get it close. Better to be a little bit rich on the high side, if you are not doing any cookie cutting races. Cookie cutting races change everything. :( It should "blubber/4stroke" out of the wood @ WOT and clean up when you stick it in big wood. Remember, If you tune a saw for big wood and are then heavy on the throttle limbing you might be running it too lean! Just always be listening. You may get tinnitus but you will blow up less saws. Like others have said, bouncing off the rev-limiting coils does sound much like a blubber/4stroke, so if you are unsure, just use a good fast tachometer, or change to a non-limited coil if it's a problem. The coil might have printed right on it what RPM it is "limited" at.
 
  • Thread Starter Thread Starter
  • #19
Great info thanks everyone!
I need to go away and digest all this and have a think...definitely no cookie racing going on.
I did mention earlier when I first got the 461 I thought it was a bit 'screamy' in small stuff...so I took it easy. I do make it a habit to listen to all my machines, one gets an 'ear' for when things are not quite right, or when I'm not sure...hence this thread!
 
Bermy said:
Great info thanks everyone!
I need to go away and digest all this and have a think...definitely no cookie racing going on.
I did mention earlier when I first got the 461 I thought it was a bit 'screamy' in small stuff...so I took it easy. I do make it a habit to listen to all my machines, one gets an 'ear' for when things are not quite right, or when I'm not sure...hence this thread!
Click to expand...
Fi, you won't have to worry about making a bad carby adjustment on your 461, just follow your 461's owners manual instructions and your good to go. With these modern saws they have so many limiters on them to avoid lean seizures the worst that could happen is a fouled spark plug from an over rich condition.
The owners manual for your saw won't steer you wrong.;)
 
  • Thread Starter Thread Starter
  • #21
Roger that Willard!

SOP is to read the manual, but good to know about all these extra things too :)
 
IMHO, tuning the high side is just as easy as tuning the low side. First video, the saw is still running somewhat fat in the cut. You can hear her break up every now and then while cutting. Second video the saw is just about perfect (for me) as she cleans up in the cut, but 4 strokes as I rotate off the dogs. When I pull them apart, there is allways a clean looking P&C thats wet and shiney, 32:1 mix and a slightly fat tune have served me well over the last 20+ years ............ the wear is virtually non-existant.

http://www.youtube.com/watch?v=LImYkWMM21U
http://www.youtube.com/watch?v=WDsCF21ZDiY
 
Trying to understand this all for me, is like someone trying to understand, from many people's helpful advice how to set up the 3:1 return on the HH with a base-tie with a back-up system. I get lost. I wish I had a local to sit down with, adjust and cut. I probably don't get all the performance out of my saws as possible, but seems to work okay now.


Can a tach even be used on modded saws? My 460 and 660 have been souped. 064 just sits after the last time I tried to adjust it. When you have souped 660, what's a old 064, for?
 
If it will make a good milling saw, I'd do that. It just seems slow. Might be THIS 064. Bought it for $300 used hard and put up wet with a bad oiler and nose sprocket.
 
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