Fuel mix ratio and carb tuning

[RI Chevy]

In doing some reading, and thinking outloud, I would just like some feedback on this. Not sure if anyone else ever wondered about the same thing.

Does one need to retune a carb based on fuel mix ratio? For example, If I had a carb tuned for 40:1, then I decided to try 32:1, do I have to retune the carb for the new mix ratio? Or will it run ok based on the previous tune?

 

[Simondo]

Yes....you need to change the tune as the more oil ..the less fuel . If i use 40.1 and set a saw (or any other machine) to that mix and then swap to 50.1 i will need to retune as the engine will run richer as there is more fuel in a 50.1 mix than 40.1

 

[RI Chevy]

That's kinda what I figured. Just thought I would ask. Thanks. [emoji106]

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[Simondo]

That's kinda what I figured. Just thought I would ask. Thanks. [emoji106]

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Some say they dont see a change between 40 and 50 .1 ...i do.. so its one of the things i need to know ..what the saw is going to run on ..to hand it back to its owner.

 

[jakethesnake]

Even changing the type of oil will throw my 346 out of whack. Sometimes it depends on the specific Saw

 

[RI Chevy]

Wow. Ok.
So basically always, always keep a check on the tune.
I do anyway, but like I said, I just thought I would post and get some feedback.
Thanks Jake.

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[angelo c]

In doing some reading, and thinking outloud, I would just like some feedback on this. Not sure if anyone else ever wondered about the same thing.

Does one need to retune a carb based on fuel mix ratio? For example, If I had a carb tuned for 40:1, then I decided to try 32:1, do I have to retune the carb for the new mix ratio? Or will it run ok based on the previous tune?

Yes

 

[angelo c]

Wow. Ok.
So basically always, always keep a check on the tune.
I do anyway, but like I said, I just thought I would post and get some feedback.
Thanks Jake.

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Jeff, there are times in a day that I will retune a saw....same saw-mix-operator. Ect.
Different humidity and temperatures changes require tunes ... FOR ME....some guys I've been on jobs with have never seen a Stihl orange screwdriver. I have one in every truck/tool box/ work station...there must be 10 in my basement alone.

 

[jakethesnake]

I have a 55 husky that never has been touched Summer winter 50:1. 32:1 runs pretty good I never touch it

 

[RI Chevy]

Thanks Angelo. [emoji106]

Interestingly enough Jake. I never really had to mess with my Stock 029 much either. I kind of set it and forget it. But that was before I was into this current fad. Lol

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[jakethesnake]

I think some carbs are just plain finicky Honestly I don't use my 346 near as much as I use the 55 just for that reason

 

[angelo c]

Thanks Angelo. [emoji106]

Interestingly enough Jake. I never really had to mess with my Stock 029 much either. I kind of set it and forget it. But that was before I was into this current fad. Lol

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I'm so bad there are times I hear a lean saw on some roadside crew I get the shakes.

 

[Tpagel]

Nice topic,
I think sometimes I need to hide my orange screwdriver and just run it.
My normal tune is a touch fat usually.
I have wondered the same thing about mix ratio. The idea being if I run more and better oil can I lean a saw out more and keep it protected?


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[cease232]

I'm so bad there are times I hear a lean saw on some roadside crew I get the shakes.

I've been tempted more than a few times to pull over and help a stranger tune their saw.
I never run a saw without a screwdriver in my pocket.


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[TreeLife]

There's 128 FL oz's in a gallon, for a 32:1 mix you use 4 oz's per gallon if I'm not mistaken. Seems like peanuts to an elephant, but I have found its really per saw/carb. Some are really picky for oil, some are really picky with various Temps.

One of my 460's doesn't give a rats azz what's run thru it or what temp it is. Always four strokes a little off pressure in the cut and cleans up. Bottom end, jug n slug are in perfect shape.

 

[RI Chevy]

TTT

 

[TreeLife]

What else do you want to know or discuss, Jeff? Happy thanksgiving by the way!

 

[smokey7]

From 40:1 to 32:1 is a pretty small change. If your tune is always on the safe side then at 32:1 it will be just a tiny bit closer to a sharp spot on tune. As for the question or statement that if using a premium quality oil at a heavy ratio like 32:1 can you run a leaner tune and still be safe. Yes i believe so. As long as your temps dont go overboard and get away from you it should be fine. Thats where redbulls testing with the thermocouple on a standard carb say would be helpful. On most 2 cycle sleds i try to stay under 1300*. They can handle hotter but the time you can keep them that hot is shorter. So i wouldn't run a milling saw right at 1300* ever due to the length of time it takes to make a cut. A cant saw could probably run 1500-1600 pretty safe due to the time it takes for 3 cuts is so quick the piston never gets heat soaked enough to start melting.

 

[RI Chevy]

What else do you want to know or discuss, Jeff? Happy thanksgiving by the way!

Lol. Happy Thanksgiving Nick.
Just to spur a little interest.
Thanks Smokey. Very informative post.

 

[Deets066]

It shouldn't matter what you are or aren't changing on the saw or mix, just always keep an ear on the tune. Like Angelo said, tune can change from morning to afternoon, just have to know what to listen for.

That being said, stock saws are usually less finicky and don't need as much attention. Ported saws... well if you have a ported saw you'd better damn well know how to tune it.