Gas oil ratio question

[SHADOW]

At Christmas eve,I was talking with my father in law
and he say to only use 1:40 ratio in my ms260.

But Stihl owner manual say to use 1:50 Stihl oil ratio
for my saw.

What are you using with your Stihl?

Why?

Thanks

[Warbird]

I have always used factory recommendations for my 2 Stihls and have had no problems.

[lumberjack48]

When a saw is still under warranty , absolutely run the mixture they call for, because this is the first thing they check is the gas, if you have trouble. A Stihl dealer was a friend so he gave me heads up how the warranty worked.
After warranty he recommended me to run 32:1 because he new how hard i ran my saws, I had a 038 Mag and a 044 Mag for 8 yrs on the job, these saws impressed me.  I used a 034S for a felling saw, i would tip up to 400 trees a day with it, in clear cut Aspen, that little saw impressed me every day, I'm pretty hard to impress. Pound for pound the fastest saw i ever had was a Lombard Lighting 3, boy she was hard on the ears, it looked like a XL12 Homelite.

Happy New Year

[Al_Smith]

 Pound for pound the fastest saw i ever had was a Lombard Lighting 3, boy she was hard on the ears, it looked like a XL12 Homelite.

Happy New Year

For all intents it was a Homey Xl-12 just larger .According to a local dealer who at one time sold Homelites that saw engine ,Al 42 series was designed by the same engineer who did the Xl-12 . Fact is If I'm not mistaken there might be a larger version also using the same time tested design .Might have been sold by Remington .

BTW if anyone owns a Comango,Lighting,Lighting II or III or super Comango they are known seal leakers .Good old cutters .I have two operational and three in parts boxes with scalded cylinders because someone cooked them,not I though .

[lumberjack48]

Thanks for the info Al, very interesting , i seen it break the start rope when i shout it off. It had more compression then any saw i have ran, it would just about tear your fingers off. I had to replace the starter rope once or twice a day, you had to seek up on it to start it. 

[Al_Smith]

I don't think they are an excessively high compression engine although they do have a lot of power for 4.2 cubic inchs . You have to keep in mind though that that engine had a 35 degree advance of spark so more than likely it would bite you at least on occasion .For what it's worth though I've had worse finger pullers .

Something I might add though on that series since it's kind of a side track at the moment .The newer models had a screwed up auto oiler that like some of the McCullochs would leak bar oil into the crankcase .Made them smoke like they were burning soft coal .Now the problem with that was not the fact if they would run because they would  but it masked a bad seal . People would get annoyed and block off the crankcase tube and just use the thumb oiler .What would happen then is they would lean out and cook the cylinder  because of the leaky seal .

In thinking this over knowing with what I know  today that is most likely why Lombard recommended them to be ran on 20 to 1 oil ratio .At that time period most other brands were at 32 or 40 to 1 .That extra little shot of oil would have most likely saved them although better seals would have been a better plan .

[SPIKER]

It has/had been recommended to me that you run the lowest ratio based on the engine MFG & oil MFG you are using.   If you read up on the oil brand you are using it should give you a mix ratio based on that oils manufacture.   They design the oil to properly lube the engine when mixed per the oils instructions. 

SO if the engine mfg says 40:1 and the oil manufacture says mix it 32:1 then I mix it 32:1.   If the engine is 40:1 and the oil is 50:1 then I mix it 40:1.   I have NEVER had an issue with any of my 2 cycle engines this way even power always seems very good.

Mark

[JohnG28]

When I mix fuel for my Stihl I use the pre measured bottles but put a little less fuel than is recommended.  For a bottle made to mix one gallon I go with around 9/10 gallon.  This makes around 45 to 1 and accounts for any small amount left in the bottle.  I also run a fuel stabilizer mixed with the fuel.

[John Mc]

Shadow -

If you use a good quality oil and keep your engine tuned properly, 50:1 ratio will work just fine. The 40:1 ratio (or 32:1 or whatever) that your father-in-law used in his younger days was likely driven by the limits of the oil they were working with back then. Oil has improved a lot over the last couple of decades. I run 50:1 in all my chainsaws. I also run 50:1 in my weed whacker (which calls for 32:1) and used to run 50:1 in a leaf blower I had (called for 40:1). I never had any lubrication-related problems with any of them. I did have to re-adjust the carb fuel mixture settings when I switched from running the factory recommended oil ratios to 50:1.

John Mc

[smalldog]

Just remember the more oil you put in the mix, the leaner the fuel/air ratio is. Your carb jets flow only so much mix, so if you have more oil, you have less fuel. So, if you have one of these newer, fuel efficient saws that are running quite lean anyways, then you mix at 32:1 instead of 50:1, you just made your fuel/air ratio 35% leaner. You may think you are saving your engine from seizing with more oil, but, in fact it may be worse unless you adjust your carb richer.

[Al_Smith]

 ??? I'd like to know where that line of thinking or thought pattern originated ?

Rich or lean regarding the saw is merely refering to the air and fuel ratio and has nothing to do with the oil ratio .The oil leaves behind a residue of microscopic particles which lube the cylinder bearing etc .Without it the engine would cease to run after a few seconds .

If one would adhere to that then the old saws and outboards would never have lasted as long being operated on 16 to one fuel/oil ratios .Fact being there are literally thousand of those old relics which still run as good today as they did 50 years ago ,heavy oil or not .

Now I'm not suggesting by any means to operate a modern saw with modern oils mixed at 16 to one .Unless you are fogging for mosquitos but it certainly won't cause one to sieze unless it were poorly tuned .Then again any poorly tuned saw stands a chance to become  door stop if tuned too lean .

[chucker]

??? I'd like to know where that line of thinking or thought pattern originated ?

Rich or lean regarding the saw is merely refering to the air and fuel ratio and has nothing to do with the oil ratio .The oil leaves behind a residue of microscopic particles which lube the cylinder bearing etc .Without it the engine would cease to run after a few seconds .

If one would adhere to that then the old saws and outboards would never have lasted as long being operated on 16 to one fuel/oil ratios .Fact being there are literally thousand of those old relics which still run as good today as they did 50 years ago ,heavy oil or not .

Now I'm not suggesting by any means to operate a modern saw with modern oils mixed at 16 to one .Unless you are fogging for mosquitos but it certainly won't cause one to sieze unless it were poorly tuned .Then again any poorly tuned saw stands a chance to become  door stop if tuned too lean .

i like your way of thinking!! perhaps this is the reason why all my "old junkers" are still in action?

[smalldog]

I'm NOT saying that more oil is bad or that it causes damage. I'm saying that if you replace gasoline molecules with oil molecules going through a fixed jet size, you ARE leaning the fuel/air mixture. If you want to send more oil through that carburetor jet, fine, just allow for the change and increase the jet size to keep the same amount of fuel. Yes, the old 2-strokes ran high amounts of oil in their fuel, but, look at the jet sizes. They had larger jets to make sure they had an sufficient amount of fuel also.

[Al_Smith]

Well firstly I'm casting espersions nor picking on anyone .

The first time I ever heard this mentioned was a certain on line personality who was so anal about things he would invaribley argue that for instance 3/8" pitch chain was not it fact truely 3/8" .The same with the oil mix ratios saying 40 to one was actualy some other ratio and argue forever he was correct and the rest of the world was wrong .I suppose he might have mixed his fuel under laboratory conditions perhaps . :

Now I could care less  nor give a hill of beans about anyones favorite oil nor how they mix or in what ratio , not my saws .I have however seen way more saws get a fried top end from a lean carb setting than from running a rich fuel/oil ratio .It may sound neat and bad to the bone running like the wind out of the wood but unfortunatley given enough time the saw will clam up and never make another peep.The sounds of silence .Then if large enough, a boat anchor, smaller a door stop . :(

[Al_Smith]

I'm NOT saying that more oil is bad or that it causes damage. I'm saying that if you replace gasoline molecules with oil molecules going through a fixed jet size, 

They aren't fixed unless they are smaller less expensive home owner type saws in most cases .That's what the needle valves are for,to adjust the mixture .

Now granted from time to time some saw manufactures had the bright idea to use fixed jets but that had more to do with stopping warentee work than any thing else .As a rule they didn't run worth a hoot though .

It makes sense that less oil in the mix would burn a little hotter the same as a lean mixture would .However going to the absolute extremes just for debates sake it would be unwise to lessen the ratio to perhaps 80 to one in the interest of providing more gasoline than oil .That would be just another boat anchor in waiting .Not good .

[smalldog]

I was just trying to bring up what I learned at Suzuki and Yamaha service tech schools. Because I had customers that depended on me to help them with their problems, I would listen in class and read the service bulletins. I had people that would take a engine made for 40:1 and switch to 100:1 amsoil and wonder why it's running rich. Or the person that has a machine made for 50:1 that runs 20:1 and cooks the top end from heat. Make sure you rejet if your changing your premix ratio. 2-stroke oil in your fuel lowers your octane rating also. That's why they say to run higher octane fuels. So you get the customer that has a MS460 with a dual port muffler cover(which will lean it), and is running regular low octane fuel mixed at 32:1(more oil=less fuel), and wonders why it has problems. A MS460 comes with about a .68mm main jet. If you mix at 32:1, that is a 1.125% increase in oil volume going through the jet which means 1 jet size increase. Some people will wrongly blame the oil for damage, when in fact the ratio and jetting was the cause.

[John Mc]

Samlldog -

I know little about small engines. However, I can follow what you are saying, and see the logic in it. If the carb is set to allow a certain amount of gas/oil fuel to mix with the air, and you put more oil in your mix, you have less gas in that amount of fuel mix the carb is metering in. Less gas = leaner burn (depending on what is happening to the oil??) I would also guess that if the viscosity of the fuel mix was changed significantly by the extra oil, that might allow less of the fuel mixture into the carb.

I wonder how significant the change is? If I tuned my saw using non-ethanol gas, then switched to E10 gas, I found I needed to tweak the mixture setting a bit richer to get back to the same place (makes sense, since ethanol is an oxygenated fuel). It was pretty subtle however - and may have even been in my mind, since I'm no ace at tuning saws at this point.

My question is, woudl you really need to re-jet the saw? Can't you just adjust the mixture a tad to compensate?

[smalldog]

Yes, you can adjust the H screw but you will notice the mid range lean like many of the new EPA saws have. You know what I mean...when you touch the wood only running half throttle and it seems the saw has no power unless your running full throttle. If you rejet, you gain that midrange torque.

[Al_Smith]

Hmm,well first of all it's apples and oranges .A rich burner two stroker motorcycle has usually had oil injection or the few I paid attention to have had for decades . Of course being an old Harley man I gave them little heed . 8)

Generally speaking a saw has two running conditions ,wide open ,let -er-rip or idle .All mid range does is get you to top speed .BTW a duel port or in fact any muffler modifications are design to allow the saw engine to breathe better .More air,more fuel but of course the carb needs to be reset , elementry . Back to that  adjustable jet thing . ;) Try as I might I can't get through my 2 inch thick scull why anybody would run a saw at half throttle for very long  ??? Unless you were limbing with an 084 or something which I'll guarantee you won't do for very long .Cruel and unusual punishment .

[smalldog]

Yes, 100:1 is not much oil. I've seen crank bearings and lower rod bearings go bad
and wrist pin scuffing on engines running 100:1 mix.

[smalldog]

Suzuki came out with a service bulletin on ethanol fuel used in premix back in the 80's. It said the problem with ethanol is it will absorb moisture and in turn, force the oil out of the premix. So, we tried it. We mixed a 40:1 premix using 10% gasahol(we tested it) in a glass container. We slowly added water to the mixture(several drops at a time). It was amazing how much water could be absorbed instead of settling on the bottom. Before long you could see the oil forming into small droplets in the mix.

[smalldog]

OK AL, NONE of the Honda CR's, Kawasaki KX's, Yamaha YZ's, or Suzuki RM's EVER had oil injection. Neither did the racing 2-stroke ATV's(like my LT250R) or the Kawasaki Jet Skis I worked on. Or the all the early snowmobiles and ultrlights I've had.

I'm not saying you HAVE to have a nice mid range, but, it sure is nice.

[Al_Smith]

 :D I'm having flashbacks I think or I've traveled this road before with  about the same success rate I'm probabley going to have with this discussion .

We should take a survey of two things .First just how many people run a saw for an extended  period of time at half throttle and secondly who would suggest that operating a saw with more oil per gallon mix as opposed to less would suggest that more would cause the saw any harm regarding a tendency to cease .

I mean for heavens sake that's about like saying it's better to straight gas them .We all know that won't work---or do we .

[smalldog]

 I'm having flashbacks I think or I've traveled this road before with  about the same success rate I'm probabley going to have with this discussion .

Ditto

All I'm saying is the premix ratio affects jetting. If you want, Google "premix affects jetting" and read for your self.

I never said less oil is better. I did say that if you have a newer EPA saw that is quite lean to begin with, increasing the oil in your premix WILL lean it out further. Just adjust your carb for the new mix.

I NEVER said I run my saw for EXTENDED periods at part throttle. I DO enjoy a saw that has a non EPA midrange (slightly richer) that will actually cut wood at part throttle. That enables me to start a cut at part throttle, then roll into full throttle.(remember the old saws?) Some of these new EPA saws are so lean at part throttle, the HAVE TO be full throttle at the very start of the cut.

[Al_Smith]

   .

I That enables me to start a cut at part throttle, then roll into full throttle.(remember the old saws?) Some of these new EPA saws are so lean at part throttle, the HAVE TO be full throttle at the very start of the cut.

:D :D Remember who you are talking to .I remember the "old " saws when they were new saws .Fact is I ran the Mac 250 about the first year they were on the market if that tells you any thing .

That aside the only" new " saws I have are the pair of Stihl 200T's .I doubt they are EPA  compliant .Especially after I got through tweeking them . 8)

Plus the fact I'm somewhat of an outlaw sawman when it comes to edicts of the EPA .Chances are if I do ever get one of those so called EPA saws its' chances of staying that way are somewhere between slim and none .

Joking aside I've never ran much less fiddled with one of those things .As I type though residing in my shed are several brand new Stihls that belong to a trimmer bud of mine .Once he gets tired of whimpy saws chances  are great the EPA wouldn't much approve of those either .Now keep this on the QT because I don't want the chainsaw police knocking at my door . ;)