New barrel and piston for Husky 365

[Ratman]

More oil, leans out the fuel, more air drawn to compensate, saw trying to find lost power, heat increases, bore suffers, from intake side more so, whilst smoking its knackers off, then the inevitable happens! A bearing implodes due to heat and stress and takes everything else out, or cylinder cops it resulting in eventual seizure and outward stress to cause everything else to shat itself. (Exaggerated worst case obviously)

[spudulike]

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!

[peatff]

12 hours ago, Ratman said:

More oil, leans out the fuel, more air drawn to compensate, saw trying to find lost power,

 

How does this saw try to find lost power does it have artificial intelligence ? I've upped the oil in saws to first run them after repair and all I find is they smoke and blow some oil out of the exhaust and sometimes oil the plug up.

[Ratman]

 
How does this saw try to find lost power does it have artificial intelligence [emoji3]? I've upped the oil in saws to first run them after repair and all I find is they smoke and blow some oil out of the exhaust and sometimes oil the plug up.

Me too regards oil and rebuild,
it tries to find the power i.e is made to work harder due to the fuel mix being leaner because of extra oil in mix, so intake of air is increased as it is gasping, which in turn ramps up the temperature. Bit like someone putting their hands round your throat, you gasp for more air and in turn you turn red and get all hot and bothered.

[Stere]

So this guys wrong:

 

https://www.arboristsite.com/community/threads/oil-mix-ratio-for-milling.81581/

 

Quote

I don't think this makes any difference unless you start operating at mix ratios below about 25:1

With 50:1 the gas represents 50/51'ths of the mix, or 98.03% is gas.
With 40:1 the gas represents 97.56% of the mix
I can't see a 0.53% difference in the amount of gas in the mix making much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the oil to gas ratio. This has to change by 10's of percents or more to make a significant difference.

I agree that if the mix is changed significantly the carby should be retuned, to whatever the powerhead needs to run smoothly. Then for milling the high end should also be richened so that the machine RPMs a little lower than at smooth max.

 

[Ratman]

So this guys wrong:
 
https://www.arboristsite.com/community/threads/oil-mix-ratio-for-milling.81581/
 

I don't think this makes any difference unless you start operating at mix ratios below about 25:1

With 50:1 the gas represents 50/51'ths of the mix, or 98.03% is gas.
With 40:1 the gas represents 97.56% of the mix
I can't see a 0.53% difference in the amount of gas in the mix making much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the oil to gas ratio. This has to change by 10's of percents or more to make a significant difference.

I agree that if the mix is changed significantly the carby should be retuned, to whatever the powerhead needs to run smoothly. Then for milling the high end should also be richened so that the machine RPMs a little lower than at smooth max.

 

Nice one Stere, that last paragraph answers what i was kinda pondering regards a saw being used for milling and the possibilities of wear / damage occurring to the bearings due to it being on its side. I get there is vacuum and pressure workings in the crankcase when running regards lubrication.
But it still made me wonder as gravity surely must play a part on the uppermost bearing on a saw when milling.

[wyk]

Yes. He's wrong. As are all folks who use the 'lean' idiology. It ignores the most basic part about chainsaw tuning. It is the air to fuel mixture that allows the chainsaw to idle correctly, climb in rpm and to four stroke at peak rpm(when tuned right) - not the oil to fuel mixture. Oil has little to do with chainsaw tuning. If your saw is tuned right, you can run nearly any ratio. That is how saws ran at 16:1 for decades before, and at 25:1 and 32:1. 50:1 is the leanest ratio manufacturers have found that will work in modern saws using fully synthetic oils. The leanest ratio they dare to use, not the optimum ratio they use. This was done to pass EPA mandated emissions. Why? Because oil burns in the mix, and introduces loads of hydrocarbons to the exhaust. In other words, oil does not lean out the mix - it is part of the mix that burns. Leaning the mix out is a myth. If it wasn't, then manufacturers would be suggesting 80:1 100:1, etc. Which, of course, they don't. When I was young, like back in the 70's/80's, no one I knew had a lean seizure(and I worked in wild land fire fighting with chainsaws in the 80's using non synthetic oils). Nowadays - common.

 

Here is a copy of my statement from the Echo 352 thread:

 

At a mix ratio of 32:1 vs 50:1, you have a difference of 1.125% more oil in the fuel mix - 3.125% VS 2%. 1.125% less petrol is not going to cause your engine to over heat or seize. However, the over all amount of oil that enters the engine at 32:1 is over half again more vs 50:1. So, at 32:1 VS 50:1 you risk an air/fuel ratio compromise of about 1% in order to get at least another 50% more lubrication in to the engine(but you really don't, as some of the oil makes it to combustion) - which is about 14.52:1 air to fuel VS what is the agreed upon 14.7:1 as the optimum fuel/air ratio for most petrol motors - assuming you do not tune your engine for your mix, and you then go from 50:1 to 32:1. Autotune and mtronic (and you, if you know what you're doing) will tune this out as you tune for RPM or 'four stroking' and idle, which is a result of the air to fuel mixture, not the oil to fuel mixture. But, as is obvious, even if you do not touch your carb controls, chances are your mixture will be more affected by a change in weather than a change in your mix unless, as Steve has stated, you start to go down to crazy ratios.

 

At the end of the day it is called mix for a reason. The oil is now part of the fuel, not a separate entity as it is metered in to the saw. Not all of the oil will shear from the fuel as it goes through the engine - only part of it does - otherwise your saw would pour oil from every orifice after a few days of hard use. Much of it is burned, which is obvious if you look at the emissions tables on 2 strokes VS about anything else aside from diesels - the carbon emissions go up drastically when you go from 50:1 to 32:1 - which make sense. If the fuel to air ratio leaned out dangerous from 50:1 to 32:1, you would have to see far, far less carbon emissions vs more.

 

If you want to avoid seizing, carbon build up, etc etc - simply use a good high-quality fully synthetic oil designed for air-cooled non-marine application two strokes at a decent ratio, and make sure your engine is tuned properly.

 

Edited March 16, 2019 by wyk

[Paul in the woods]

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?

[Ratman]

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?

Stick with it. The talk above is a generalisation on what would happen if changes WERE made. I’m still learning with it all, enjoying it too [emoji106]

[spudulike]

Sounds like WYK and I agree on the oil rich mix leaning a saw theory lauded by some. I have never seen a saw heavy with oil having seized. Most are poor carb adjustments, air leaks, fuel delivery issues or old/straight fuel. None have been oily and seized.....never have got that statement used by some.

Stating "Fuel" with two strokes means OIL & Petrol not just Petrol! that is key!