Converting 50:1 to 40:1

[Husky187]

Hello all, the question of tuning still baffles me from time to time and I would like to fully understand exactly how to precisely do it. Currently on two of my saws (372xp and t435) I run a 50:1 mix, and on my other two (346xp and ms200t) I run 40:1 one.

I would like to run them all on the same mix, two gas cans is annoying to lug around. I know it has been said that running a 50:1 on 40:1 mix is a big no no but 40:1 on 50:1 is okay.

Is it worth running one mix over the other? I understand that running wide open to adjust the H screw for lean or rich (little or more fuel) and then on the idle adjusting the L screw accordingly. Then the final screw T is for the adjustment of idle RPMs - correct me if I am wrong.

Just trying to get a good definitive answer on which direction to go with the saws, without having the expense of seizing any up to learn. Appreciate any input.

Thanks.

 

[P.M.P.]

Just run your 40:1 in all of them and if you can't get e free gas in your area run premium. Then just retune.

32:1 MAXIMA K2 E.FREE FTW

 

[RIDE-RED 350r]

Just understand that when you switch a saw that has been running 50:1 over to 40:1 you will need to re-tune. More oil in the fuel mix at 40:1 will lean your combustion mix slightly. Generally, going from 50:1 to 40:1 will not be enough of a change to guarantee a burn-down if you don't re-tune, but just the same, re-check your tune.

I used to run 50:1 per Husky recommendation. But since I modded two of my four main saws I switched to 32:1, which I run in all of them now including my stock (for now) 346 and mostly stock 359. My modded saws are spinning about 14K+ RPM for work, and a bit higher for testing and playing around. The moving engine internals will be better served with more oil running at higher RPM.

 

[Husky187]

When readjusting for the 50:1 - 40:1 conversion should I back my H needle out more as to richen the mixture more?

 

[Joe Kidd]

When readjusting for the 50:1 - 40:1 conversion should I back my H needle out more as to richen the mixture more?

Yes. Maybe no more than 1/8"-1/4" turn. The saw should "4-stroke slightly" out of the wood and smooth up when just in the wood. H needle adjustments are difficult to tell you "how much" to turn. Listen and tune the saw in and out of the wood. Youtube has some videos showing saw tuning which may be helpful. Be mindful it's better to err on the rich side if learning saw tuning.
Ambient temps can also affect tuning and weather conditions. Keep the screwdriver handy.

 

[Duane(Pa)]

You can do a lot more harm running lean than running rich. Back the H screw out and dial it "in" from rich to just right. not vice versa. Remember temperature affects tune. More fuel needed in cold air. You will be surprised how much affect a small change in the H screw has.

 

[RIDE-RED 350r]

Not only that, but you need to get the saw fully up to operating temp and under a load. Make a few cuts with it set safely rich, then tune it. What might be a good tune firing up a cold saw and wacking the throttle after a brief/non-full warm up will translate to a lean condition when working the saw under a real load and fully up to temp.

 

[bikemike]

I'm a 40.1 guy. But now I have been running 50.1 in my saws. But I'm also using amsoil Saber 100.1 at the 50.1 ratio.
It's some good stuff and lubricates very well, smells good,

 

[Husky187]

I currently am running Klotz Original Techniplate. Here in NEPA it's been in the low 30's for running, just trying to get the firewood pile up a little more, and have a few dead logs that need to be trimmed up. Wondering if the risk of tuning is worth it now...

 

[RIDE-RED 350r]

You should be just fine. Tune the saw and cut that wood.

 

[Husky187]

My main goal after getting the 40:1 mix into the other saws it that to stay on the safe side they are running rich and not leaned out.
I assume I would want to tend to stay on the H screw with the weather being colder now?

 

[RIDE-RED 350r]

Cold air is more dense than warm air.. so yes, when we tune for temperature, colder air requires a richer setting. With a stock saw this will not be a drastic adjustment.

Do you still have the limiters on your carb??

If yes, I would recommend cutting the limiters off so you have all of the adjustment available your saw needs. Once those are gone, just set the saw safely rich and make a few cuts to get it warmed up. Then start dialing it in listening for at least slight 4-stroking at WOT no load. If you feel like you want a bit more 4-stroking, by all means go for it. You will never hurt your saw running it a bit on the safe side. And setting it a little on the safe side you will be less likely to have to re-adjust when the weather changes. If you are tuning for max performance on the edge, you will need to pay closer attention to your state of tune and re-adjust more frequently.

 

[Husky187]

I assume the limiters are still on the carbs. Never cared to mess with them because there was never an adjustment issue. Always seemed to be getting the most on them. Nothing gets abused but it is definitely used. I'll try to mess around with it over the weekend, and hopefully get a video of everything running as it, and see which direction I need to go. Great info so far.

 

[MustangMike]

I run Saber at 40:1 in all my saws.

H screw for lean or rich (little or more fuel) and then on the idle adjusting the L screw accordingly. Then the final screw T is for the adjustment of idle RPMs - correct me if I am wrong.

The H screw is for adjusting rich/lean on the Hi speed circuit, the L screw is to adjust rich/lean on the low speed circuit, the third screw (often labeled LA on Stihl saws) is the idle adjustment screw.

When adjusting the H, the saw should break up a little at WOT when it is not in the cut, and clean up in the cut. If it does not break up it is too lean, if it does not clean up in the cut it is too rich.

Adjusting the H properly is very important, if it is too lean you WILL burn up your saw.

 

[CoreyB]

Your t435 may not get hot enough or put under enough load to burn clean with a 40:1 mix depending on oil used.

 

[bikemike]

I run Saber at 40:1 in all my saws.


The H screw is for adjusting rich/lean on the Hi speed circuit, the L screw is to adjust rich/lean on the low speed circuit, the third screw (often labeled LA on Stihl saws) is the idle adjustment screw.

When adjusting the H, the saw should break up a little at WOT when it is not in the cut, and clean up in the cut. If it does not break up it is too lean, if it does not clean up in the cut it is too rich.

Adjusting the H properly is very important, if it is too lean you WILL burn up your saw.

Only reason I went to 50.1 on the saber is cause my top handle saw takes a few cuts to clean out, in a tree it's not always an option. Use to run the echo powerblend at 40.1 no problem with clean out. The saber is so much more slick and oily when you have a spill our leak and the gas evaporates away. I like the saber

 

[bikemike]

Your t435 may not get hot enough or put under enough load to burn clean with a 40:1 mix depending on oil used.

Stihl and Echo oils 40.1 will clean out fine. The saber takes a bit at 40.1 50.1 is fine. And is twice the recommended ratio the saber suggest

 

[jake wells]

i run 32:1 in everything i guess im doomed.

 

[bikemike]

Stihl and Echo oils 40.1 will clean out fine. The saber takes a bit at 40.1 50.1 is fine. And is twice the recommended ratio the saber suggest

Plus amsoil Saber reps say if your motor isn't old and you run it at 100.1 and a internal failure happens due to not enough lube they will take care of it. Makes me want to run a leaf blower on it they are under load from the time they are fired up

 

[Al Smith]

i run 32:1 in everything i guess im doomed.

Me too,we're both in the soup I guess .

Then again being a dumbazz somebody is going to have to explain to me how running a richer oil mix could cause a lean burn .If that were so I'd have thought those old Johnson and Mercury boat motors would have seized up.How they ever kept running for 50 some years remains a great mystery .Oh not to mention ,right from the book on McCulloch go kart racing engines they recommended 20 to one .How is that so ?BTW that was racing oil not SAE 30WT .