I agree. A great mechanic can listen a tune. Too many newbies are buying tachs, and assuming they are doing right by an engine...
Spark Plug Wisperers?
- Thread starter MAWoodsman
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Audible tuning is very much subject to interpretation. A tach isn't. I don't know how you make the jump that tuning by sound is better for newbies.
I tune by ear to get in the ballpark, but the real tuning is really done next when it’s under load. Finally confirm with a tach.
Every engine is different, some like to be richer up top and some leaner, some like a richer idle others a leaner one. I have found barrel type carbs prefer a leaner idle while the butterfly carbs that have progressive drillings generally like to be a bit richer.
Although tuning by sound and feel by experienced user is better than a generic number from a tack, it takes time and experience.
If you’re new, get a good tach and set it to 500-1000 rpm below max.
2 stroke air cooled engines like to be run on the rich side for best power and cooling, but that’s often still leaner than the majority realise or run themselves.
Edit:
Regarding spark plug colour alone, as bwalker said, don’t waste your time.
Every engine is different, some like to be richer up top and some leaner, some like a richer idle others a leaner one. I have found barrel type carbs prefer a leaner idle while the butterfly carbs that have progressive drillings generally like to be a bit richer.
Although tuning by sound and feel by experienced user is better than a generic number from a tack, it takes time and experience.
If you’re new, get a good tach and set it to 500-1000 rpm below max.
2 stroke air cooled engines like to be run on the rich side for best power and cooling, but that’s often still leaner than the majority realise or run themselves.
Edit:
Regarding spark plug colour alone, as bwalker said, don’t waste your time.
Curious how they think the factories tune them. Some little old lady with hearing aids I suppose.
MAWoodsman
ArboristSite Member
Ok, I questioned it because I stated in my original post that both of these saws are ported/modified.
In your experience, after porting or doing a muffler mod, are saws a little rich?
Husky77
ArboristSite Operative
Years ago a dealer not far from me had a boy working with his (and still is) he looked at my saw one day and tuned it by ear. Being young and keen to learn I said how do you know the revs are set right without a tachometer. His words, I been doing it a long time pass me the tacho. He held it next to the saw and sure enough it was stop on. Some people know and understand a two stroke and some just dont and never will. As long as it starts and runs the average jo just runs it and when it stops takes it to a shop. The manufacturer goes a long way to develop a good saw, stick to their recommendations and you wont go far wrong. If your cutting for a living you dont want to be fiddling with a screw driver all day.
Have fun & stay safe
Have fun & stay safe
Setting to the factory no load setting is plenty safe IME. No need to set it 1000 rpms richer.
Myself I use a tach and set to the factory spec I then fine tune by feel and record the number like I mentioned. It's then easy to get repeatable results from a tach going forward.
One thing that most guys dont understand is that a state of tune is very transient and often changes from morning to lunch and for sure change with temperature and humidity. Carbs are not a set it and forget it type thing.
All of this is why Autotune and Mtronic area good thing...
1 in 50 can do that repeatedly.
In most cases when you port a cylinder you increase the vacuum that the carb sees. This pulls more fuel through a given "jet" size. As a result you often have to lean them up from stock saw settings. In addition ported saws often function at a higher peak power rpm. They need to be tuned accordingly.
It should be stressed that paying for a port job and then not taking the time to tune the saw properly is counter productive.
I think the part about tuning them 500 RPM richer is because many of us are never going to put the saw in a stick of wood. All stock saws come with carb limiters anymore and it is wise to just set it all the way on the rich side of the limiter. I rebuilt a MS361 the other day and it was turning 13,900 all the way against the limiter which is probably why it scored to start with. So, I ground the tab off and set it at 12,900 , or thereabouts.
They will increase in RPM once they come up to operating temperature. So, unless you have time to run every saw you fix you fudge on the rich side.
They will increase in RPM once they come up to operating temperature. So, unless you have time to run every saw you fix you fudge on the rich side.
I gotcha and you are right the saw has to be up to full operating temp prior to tuning.
I also suppose that most of the guys that take there stuff in to be worked on are never going to touch the carb anyways so running it pig rich is a good idea.
13900 on a 361 isn't dangerously lean IME. Of course if that was 13900 prior to a full warm up it may have become dangerously lean when warm.
Air leaks are what kills the majority of saws that seize. Which is another reason not to use ethanol gas unless you absolutely have to and to preemptively replace rubber parts on well used saws.
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I would put it to you that straight/incorrect fuel mix and overheating kill just as many if not more saws that air leaks if we count all saws from box store cheapies up to top pro level sold to all levels of users.
The scrap piles and skip bins of any saw shop should confirm this and the vast majority will be small consumer uneconomic repair saws previously owned by very casual saw users.
But, this is a thread started about two spark plugs and their combustion waste colour- we have digressed into how I tune things and this way is the right way.
If whatever system used works for the user and their tuned equipment does not blow up- it works.
Thats Mechanic 101. Every engine suffers wear of the cylinder, rings, and piston skirts. They get old. Tuning to the ear, essentially is how to best determine what the engine wants, NOT what its 20 yr. old manual spec. says it should be. Tach tuning is certainly the preferred method, with a perfect engine, new fuel system, and clean air filter........and no muffler mod. For the newbie with little experience at small engines (Little meaning less than 20 yrs), its another ghee-whiz look at my bench feature. Knowledge is power; tools aren't.
Not sure what is subject to interpretation. ALL ears hear........and all experienced mechanics listen for that sweet spot......
The sound...
A tach reading compensates for wear or any other changes in condition as well...
You guys are grasping and I bet most of you can't tune a saw as well as you think..
I have been tuning saws or go kart engines for 50 years. 13,500 scares the hell out of me.
The only way I'll even get close is with a tach. Otherwise I would be at 12,000 and if you knew the difference you would be tuning it yourself to start with.
When tuning for peak speed the last Ms260 I had liked 14,800 if recall. At that RPM you can't really tell much by sound.
I'd rather know exactly where I am at than guess and I would rather not tune a saw by pouring the fuel to it until it misfires, which is what "four stroking" is.
I've been tuning two strokes since the early nineties snd have used many different methods including egt guages and data loggers. I'm somewhat obsessed with it.
You might be right on straight gassing. A friend bought a new Ms440 years ago and was about to run it with straight gas before I told him he had to mix oil with his fuel. He replied that he did add oil to the motor...referring to the bar oil tank.
We’re splitting hairs here. There is a fairly large window where a 2 stroke will run just fine. Only just cleaning up under good load, through to cleaning up as soon as it touches the log. Neither will cause damage to an engine, we all just obsess about it too much. If you’ve got experience use all means at your disposal, sound, feel under load, how it responds after a cut and a tach. If you don’t have experience, stick a tach on it.
