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New barrel and piston for Husky 365


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10 hours ago, Paul in the woods said:

I'm still a little confused. If I'm milling with a modern 80cc saw that the manual states use a 50:1 mix and I'm using good quality fuel and a good quality synthetic oil such as Stihl HP utra what mix should I use? Stick to 50:1, or use more oil 40:1, 30:1?

Husqvarna suggest using 32:1 in their manuals as well as 50:1. I can not find a suggested ratio for milling as milling is not even mentioned in the owners manuals I have here.

 

Modern chainsaws are not designed for milling. Mills are designed for milling. Chainsaws are designed mainly to idle, and then occasionally make a few cuts at WOT, idle some more, repeat(and, if you like to run Sabre at 100:1 - seize up somewhere in there). Chainsaw milling is WOT for very long cuts.

 

Let's do some sitting and thinking here... which operation will produce more heat? CSM, of course. Anyone experienced at milling will either run more oil in the mix, or tune their saws to run richer(lower top RPM, which means more oil in the mix reaches the engine per rpm), or both. 40:1 full synth and 11.5-12K rpm on an MS660 or 288xp/3120xp is very typical. That is much more oil than MTronic is going to suck in to the saw at 50:1 with a WOT closer to 13.6K RPM. On top of that, MT and AT are going to be running at 14.7 or so to 1 VS maybe 13.6:1 - a far leaner AF ratio, which means higher temps for milling. What you are trying to do with milling is not only lubricate the engine, but also keep it cool as possible. With an mtronic or AT machine, you don't get to tell it what rpm to top out at(yet). You have to run more oil if you want to introduce more oil in to the chassis. How much more? Fucked if I know - I don't dare mill with an electronic carb saw...I even see folks that do chainsaw carving set their saws up very rich since they often are at partial throttle. Yes, you will foul plugs occasionally, especially when you are on the front of the curve. But a 5 pack of NGK BPMR7A's is a tenner. A 3120XP isn't.

 

The idea of lean seems to originate from folks that do not understand the fact that oil BURNS in a chainsaw, or maybe have never used a chainsaw before uh.. 1997 when 30 and 32:1 were common. Maybe someone in the modern courses is talking shit? I dunno. What you need to come away with is the fact that oil doesn't always shear out of the mix in to the chassis. Thus, a good part of the oil makes it to the combustion chamber. When you tune a saw, you are tuning for fuel air mixture. Much of that oil in the mix is in that fuel that reaches the combustion chamber. If the saw is lean, it's due to the tune, not to the mix.

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On 15/03/2019 at 20:34, spudulike said:

Well try a 25:1 mix in your saw and let me know when this happens, has anyone seen it actually be the route cause of a seize, what about WYKs millers, surely his 16:1 man must get through a saw per week!!!

I know what you are saying but the heat is caused by too much air and not oil, both will have different effects on combustion!

OK, so no one reads owners manuals. I know...I'm old and have nothing better to do when I am popping Ibuprofen during my extended lunch breaks. But hear me out:

 

Open up your Husqvarna owner's manuals and flip to the page about mix. It states there clearly to use a mix of 50:1. If it is not Husky brand oil, you are to use 33:1(this includes other full synths) or even _25:1_. Why would a company state in their own literature(owner's manual, no less) you should use more oil in the mix if it is different from one they've tested and approved other than the fact that maybe they are pushing the limits of lubrication at 50:1? Yes, they do want to sell their own oil, but that likely doesn't mean they also want you to destroy your saw if you don't.  And they are stating this right in their own literature. They aren't suggestion 25:1 because it will lean out the saw and destroy it. The manufacture themselves are suggesting it to prevent premature wear and promote proper lubrication because there are so, so, so many choices in oil out there, and so very little knowledge about their usage.

 

Go to page 25 of the 365,372 operator's manual for the reference:  http://www.husqvarna.com/ddoc/HUSO/HUSO2004_EUenAPen/HUSO2004_EUenAPen__1140206-26.pdf

 

If HUSQVARNA two-stroke oil is not available, you may use another two-stroke oil of good quality that is intended for air cooled engines. Contact your dealer when selecting an oil. Mixing ratio 1:33 (3%)-1:25 (4%)

 

 

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Sniff!, why do I not unreasonably suspect that stating "any other oil" must be mixed at 33:1 has, at least,  2 positive effects;

(i) The saw will not run a well at 33:1 mix,

(ii) it will cost more for the greater quantity of  2S oil required,

ergo, the gullible owner will buy the Husquvarna oil.

I simply cannot see how any modern computer designed or optimised for a particular mass market application 2 stroke engine, is any different from any other.

Ditto for reputable mass market 2S oils designed for particular applications.

Pure happenstance I run Stihl oil in a Stihl saw, but adhere to the view that good oil is good oil, when used within its particular  manufacturers recommendations or specifications, regardless of the branding.

Marcus

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More lube is a good thing, but as stated by others, it does change your Mix ratio,

which you should bring back into line, as that bit of extra oil does lean the saw and

that is not good, if your on 50:1, and want to use 40:1, make your saw rich by turning out the High screw, a little, just enough to ensure it is four-stroking a tad too much, then add you newly Mixed 40:1, the saw should still be four-stroking, if not you still need to give it a bit more fuel, may be even on the Low screw too, depending on whether or not the saw is bogging down when going from idle to full throttle, if its not bogging down then give it more juice on the High until the engine four- strokes, it probably wont take much if your saw was tuned right for milling to start with, but it should be addressed.

Its better to foul a plug if your adjustment is too rich or you are running too much oil than to fly the saw, a plug is a lot cheaper, looking at your plug if your not sure of your tune is a good thing, it will soot up in no time if you are running too rich, when you think your tune is spot on, check the plug after a tank, that plug will tell you what you need to do. You should not need much adjusting of the H, and may be none on the Low going from 50:1 to 40:1 unless you were running too lean to start with, otherwise you will need just a little to get her four-stroking again. Not suggesting anyone do this, but I doubled the 50:1 dose just to show someone what is possible, I still had less smoke than people I see using their saws every day, almost undetectable, but the saw was tuned to run it, more fuel added as mentioned above, no that was an extreme example just to demonstrate that normal amounts of oil and proper carb adjustment is achievable and definitely advisable.

Edited by Echo
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7 hours ago, Echo said:

"as that bit of extra oil does lean the saw and

that is not good,"

I think we have to be careful about saying it "LEANS" the saw as "LEAN" is used in two strokes to describe the relationship between AIR and FUEL with FUEL being the liquid we pour in to the tank and not the components of the fuel - oil and petrol.

All we are leaning when we add more oil to the fuel is the PETROL content in relationship to the air content and are replacing the petrol with oil. Unless the extra oil changes the atomisation of the fuel vapour to the extent it doesn't flow through engine in the same way or the oil heavy fuel doesn't flow through the carb in the same manner, the amount of fuel delivered will stay the same so the air to FUEL ratio will stay the same so no leaning.

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33 minutes ago, spudulike said:

I think we have to be careful about saying it "LEANS" the saw as "LEAN" is used in two strokes to describe the relationship between AIR and FUEL with FUEL being the liquid we pour in to the tank and not the components of the fuel - oil and petrol.

All we are leaning when we add more oil to the fuel is the PETROL content in relationship to the air content and are replacing the petrol with oil. Unless the extra oil changes the atomisation of the fuel vapour to the extent it doesn't flow through engine in the same way or the oil heavy fuel doesn't flow through the carb in the same manner, the amount of fuel delivered will stay the same so the air to FUEL ratio will stay the same so no leaning.

Adding more oil to a given amount of petrol, and not adjusting the carb to compensate, means the engine sees less petrol, and a little more oil, its the petrol that fuels the engine and it must be brought back up to the correct level or the engine will run leaner, because the air to fuel / petrol ratio has been changed.

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The air always remains the same as it goes through the carb, sucked in by the piston going up in the cylinder producing a vacuum in the crankcase. All these are constants, set by the bore of the carb, crankcase volume, bore volume, RPM etc etc. The carb dispenses the fuel in to the engine so if the ratios of oil to petrol change, unless the viscosity of the fuel changes radically, the same amount of fuel is dispensed in to the engine as dictated by the setting of the carb screws.

So......if you are changing the ratio of petrol, air and oil by changing from 50:1 to say 40:1, the ratio between fuel and air remains the same so my comment is that "leaning" in two stroke terms means reducing the amount of fuel let in by the carb or a mechanical issue letting air in to the engine where it shouldn't and doesn't relate to the air to oil or air to petrol ratios.

The prime effect of a lean mix is an increase in engine RPMs, this produces more heat and eventually fries the piston through the piston material melting.

If you stick more oil in your fuel, it is more likely to foul the plug more readily lowering revs rather than raising them!

Lean = too much air or too little fuel

 

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So the extra oil added to the petrol, does not somehow go through the carburettor,

because if it does, it has got to have ousted the same amount of petrol in doing so,

as said, constants at work, same amount of air sucked in, and same amount of drag

through the carb, thus the same volume of fuel mixed with oil get sucked in, except now there is less fuel and more oil passing by the needles.

Yes, plug fouling is also a result of too much oil, as is ring sticking and carbon build up, its a fine line, but if in doubt I would add a little extra oil than go the other way.

The new oils though do seem to be better at their job.

I have ran Two liters through a small Echo CS 352, the fuel can was clean,

that fuel was finished this evening, I put my finger into the fuel can and rubbed around the top of the can, was delighted to find an ever so slight oily film all over the inside of the can, this came from shaking the fuel before fills, just a couple of swishes, amazing stuff, the plug in the saw is in great shape, that was 50:1, I now have a mix of 40:1 ready for tomorrow, so will be able to see how this changes the tune of the saw, same petrol, same oil, just different ratio.

To me there is a fine line, and there is basically three options,

#Use 50:1 or whatever the manufacturer specifies and tune correctly

#Use 50:1 and tune richer to aid lubrication, cooling, and run slightly slower

#Use more oil in your mix and tune to your four-stroking

Option Three is the one I like, but One and Two are also good options, and based on our needs and our experiences we each have to choose for ourself.

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