2 Stihl 090's 50" bar White Ash

[Rusty-880]

I know a lot of think it's boiling inside the container, but to be boiling it would have to continue to bubble long after the cap has been removed.

QUOTE]

It was boiling, tank was fairly warm to touch and bubbled away for a good few minutes. My main thought on extra oil was to give it a bit more lube so there might be a bit more chance that it would'nt seize.
When it comes to race cars, chainsaws ect tho you only want to tune for max power. Under that kind of load you will only damage it and probly take longer and use more fuel because you have less power.
To an extent the more power you have the more fuel efficient it is. (Dosn't work as hard to do same amount of work)

 

[BobL]

It was boiling, tank was fairly warm to touch and bubbled away for a good few minutes.

My main thought on extra oil was to give it a bit more lube so there might be a bit more chance that it would'nt seize.

Unless straight gas is used, it's not the lack of lube that is the prime cause of seizure but the temperature. A two stroke needs very little lube to run even under very hard loads provided it is well cooled and well tuned. A CS will even run on 100:1 but at those ratios there is very little room for error so that's why most manufacturers generally recommend 50:1. It would be interest to know why they tell operators, who wish to use anything other than their brand lube, at 25:1, is beyond me. I can't help thinking it is to provide a financial incentive for operators to use their branded product.

The point I'm trying to get across, especially to newbie millers, is that significantly reducing the mix ratio and not re-tuning (to make up for the fact that reducing the ratio leans the mix) can contribute to seizure. Although it's still a good idea to retune, going from 16:1 to 25:1 changes the mix ratio by 2% which is within atmospheric press change tolerances so the chance of problems are low even if the saw is not retuned. Going from 50:1 to 16:1 is a 4% change, which when added onto anything else that is on the lean side and can cause problems. This can be something a simple as running the CS on it's side too close to the ground so the CS is inadequately cooled - I've seen this happening with people milling on their knees and the log on the ground with the mill and the saw almost touching the ground. Yet another good reason not to mill on the ground.

When it comes to race cars, chainsaws ect tho you only want to tune for max power. Under that kind of load you will only damage it and probly take longer and use more fuel because you have less power.
To an extent the more power you have the more fuel efficient it is. (Dosn't work as hard to do same amount of work)

I don't quite understand what you mean?

In a stock form and tuned for max power most CS used in CS mills run the risk of overheating and seizure because they are not designed to run in mills. Unlike a motor vehicle which generally has more than sufficient cooling capacity at max power, one need equal to or maybe greater than requiring max power when milling with a CS is keeping the saw cool. A simple way to do this to stock saws is to run the saw a little richer since the unburnt fuel helps carry away additional heat. This is why extreme porting (even more "extra max power") is not advisable for a milling CS. Just lowering the mix does nothing for cooling since the extra lube carries away very little heat and is in fact unnecessary for lubrication.

The other way to cool a stock saw is to open up the muffler - it's one of the few mods that, provided retuning takes place, can generate more power and cooler running. Some mild porting can also probably help do the same thing.

 

[masculator]

Correct me if I am wrong but I thought the boiling point for petrol was between 75 and 85 degrees celsius, depending on a number of factors (been a long time since I worked for shell) vaporisation, like when boiling water, will occur at a lower temperature, which will increase the deterioration of the fuel and speed the drop of octane. It also reduces the ratio of volatile elements in relation to oil so if for instance you mixed at exactly 50 to 1 after 15 minutes in the can in the sun you may have lost say 5 percent (completely hypothetical figures) of the volatile hydrocarbons but retained 99.999% of the heavier lubricating oil (which has a much higher evaporation point) you may have reduced your mix ratio to say 45 to 1, and the octane rating of the fuel may have dropped 1 or 2 points (maybe even more.) and this is why I only mix what I will use and put the excess through my mower with a low tech briggs and stratton.

 

[masculator]

.... It would be interest to know why they tell operators, who wish to use anything other than their brand lube, at 25:1, is beyond me. I can't help thinking it is to provide a financial incentive for operators to use their branded product.

The main reason that they do this BobL is the fact that in some countries such as PNG and The south americas, and african countries they use the same oil to lube their bar as they use to mix their 2 stroke, and this may be anything from rockdrill oil to gear oil or in some cases virtually crude oil. there are also some companies that produce very low quality 2 stroke oils (Lacking the solvents that keep the oil in solution with the fuel, again normally in the lesser developed countries.) Hence it covers their ass as far as warranty goes.

 

[masculator]

yup,,and me thinks the extra rich oil to gas mix helps out plenty also--

You can suck that oil smoke down olyman, I get a bad enough headache at 40 to 1, and when I have run at 25 to 1 it was eye watering and I could almost feel the oil dripping off me after 2 tanks. NOT for me thanks, I use the good oil and warranty covers it, or I fix it (not that I have to EVER due to fuel issues.)

 

[Rusty-880]

You can suck that oil smoke down olyman, I get a bad enough headache at 40 to 1, and when I have run at 25 to 1 it was eye watering and I could almost feel the oil dripping off me after 2 tanks. NOT for me thanks, I use the good oil and warranty covers it, or I fix it (not that I have to EVER due to fuel issues.)

You guys must have some serious sensitivities to oils/petrol. I cant change rods in the carb on my chev without gotting crook and running a saw has never made me crook, no matter what mix im running.
I ment when you are running something like a saw or race car (something under a decent load and working hard) you never try and tune for economy, always best power setting- usually fractionly rich.

 

[BobL]

You guys must have some serious sensitivities to oils/petrol. I cant change rods in the carb on my chev without gotting crook and running a saw has never made me crook, no matter what mix im running.

Yep I admit I'm probably more sensitive than most operators, even drying oil based paints make me sick. Some say that chemically sensitive people are similar to how canaries were used re in minesites. When I work on engines in enclosed spaces I need really good ventilation - I usually put my dust extractor on and place a flexi hose inlet on the bench.

 

[betterbuilt]

Most of the furniture I build is for the chemically sensitive. All the finish I use is No VOC. I have to go through a long and painful process of eliminating a bunch of different factors.

I wouldn't call myself sensitive but, I would say I'm more aware than most.

 

[mtngun]

Correct me if I am wrong but I thought the boiling point for petrol was between 75 and 85 degrees celsius,

Good question, thankfully we have the internet at our fingertips.

Apparently, there is no easy answer, because of all the added ingredients.

Winter gasoline is different than summer gasoline. Winter blends contain stuff like butane and iso-butane to make it vaporize readily in cold weather.

 

[BobL]

The main reason that they do this BobL is the fact that in some countries such as PNG and The south americas, and african countries they use the same oil to lube their bar as they use to mix their 2 stroke, and this may be anything from rockdrill oil to gear oil or in some cases virtually crude oil. there are also some companies that produce very low quality 2 stroke oils (Lacking the solvents that keep the oil in solution with the fuel, again normally in the lesser developed countries.) Hence it covers their ass as far as warranty goes.

I re-read a recently downloaded 880 owners manual and cannot find any reference to using non stihl lubes at 25:1.

No mention of 25:1 and all lubes to be used at 50:1

 

[Rusty-880]

The owners manual that came with my 880 said Stihl oil 50:1 all other brands 25:1. Bought it nearly two years ago. From what I've been told Stihl oil is made by Castrol.

In the local Stihl shop there is a thing on the counter from BP that says about what happens to fuel as it ages, I only had a quick look but it just sounds like the octane rating gets higher.

I wasn't having a go at anyone over fuel/oil making them crook, if I get a small amount of fuel on me it affects my nerves really bad, REALLY bad. Same goes for any chemical.