First tank of fuel

[Leather Face]

Hey,
I've been using saws for a number of years, I'm no amateur with them. However, I just bought a new saw and the guy who sold it to me told me to run the first tank of fuel rich. Is this a good idea or what? I feel stupid for not knowing but that's what we're here for right?

 

[Haywire Haywood]

When I bought my first saw some years ago, the dealer told me that the carb was set a little rich for the break in period... several tanks worth... and to bring it in afterward for him to lean it out to the optimum setting.

Ian

 

[Four Paws]

Hey,
However, I just bought a new saw and the guy who sold it to me told me to run the first tank of fuel rich. Is this a good idea or what?

Well, run the carb set rich, not the fuel mixed 'rich' (eg: 16:1). More oil in fuel = lean. Might not make sense, but remember, you are talking about your air/fuel ratio when one specifies rich/lean. 40:1 seems to be the preferred ratio by many, using a high quality synthetic oil and good pump gas (no ethanol or ethanol blends). 40:1 with your carb set rich (eg: more fuel than needed per volume of air for a stoichiometric burn) will help your saw during the break in period. It will also help as the saw tends to 'lean' itself out as it runs in. Haywood spoke of taking his saw back to the dealer to be readjusted and timed after break in, and that is why. The saw will actually start to run faster and faster due to less internal friction, and leaner fuel/air ratio. Did I make sense?

 

[Leather Face]

Well, run the carb set rich, not the fuel mixed 'rich' (eg: 16:1). More oil in fuel = lean. Might not make sense, but remember, you are talking about your air/fuel ratio when one specifies rich/lean. 40:1 seems to be the preferred ratio by many, using a high quality synthetic oil and good pump gas (no ethanol or ethanol blends). 40:1 with your carb set rich (eg: more fuel than needed per volume of air for a stoichiometric burn) will help your saw during the break in period. It will also help as the saw tends to 'lean' itself out as it runs in. Haywood spoke of taking his saw back to the dealer to be readjusted and timed after break in, and that is why. The saw will actually start to run faster and faster due to less internal friction, and leaner fuel/air ratio. Did I make sense?

Perfect sense, thank you. I've used saws since I was a kid but this is the first new saw I've had, thanks again for the good explination.

 

[Elmore]

I ran two gallons of fuel at about 26:1 when I first got my Makita DCS 520i. After that I leaned the ratio to 32:1. As long as the carb is adjusted properly I don't see a problem running your first batch of fuel with a rich ratio. I have heard that this is a good way of breaking it in. Correct me if I am wrong.

 

[Haywire Haywood]

I ran two gallons of fuel at about 26:1 when I first got my Makita DCS 520i. After that I leaned the ratio to 32:1. As long as the carb is adjusted properly I don't see a problem running your first batch of fuel with a rich ratio. I have heard that this is a good way of breaking it in. Correct me if I am wrong.

If I read the other post right, when you mix the fuel with more oil (26:1) you are reducing the amount of gasoline per volume of mix and are actually running "leaner" than say 40 or 50:1. The idea of running rich is to adjust the carb for more mix per cycle rather than changing the ratio of the mix itself.

I see what you mean tho... run the mix 'oil rich' and also enrichen the carb adjustments.

On another thread, someone broke down what difference it makes between running 32,40, or 50:1 as far as the "octane" of the mix and the burnable fuel available and it was, from a practical standpoint, negligible.

Ian

 

[coveredinsap]

Uh, the more oil in the mix, the more lubrication for the engine, and the less likely to seize up the piston. (And more leeway you have for improperly adjusted carbs)
I run all my old saws (more than 15 years old) at about 15:1, and new saws at 32:1, and adjust the carbs accordingly to run properly on those mixes.

The less oil in the mix, the less lubrication for the engine, and the more likely to seize up the engine. And less leeway you have for improperly adjusted carbs.

But what the hell do I know....I'm just a carpenter.

 

[Four Paws]

Uh, the more oil in the mix, the more lubrication for the engine, and the less likely to seize up the piston. (And more leeway you have for improperly adjusted carbs)
I run all my old saws (more than 15 years old) at about 15:1, and new saws at 32:1, and adjust the carbs accordingly to run properly on those mixes.

The less oil in the mix, the less lubrication for the engine, and the more likely to seize up the engine. And less leeway you have for improperly adjusted carbs.

But what the hell do I know....I'm just a carpenter.

Well, I think you have been breathing too many fumes from that 16:1 mix. Seriously now - when an engine lean siezes, it means it is not getting enough fuel. Not enough fuel per volume of air is the result of a poorly adjusted carburetor. Mixing your gas (on a new saw) at 16:1 or 24:1 or 32:1 or whatever:1 when it calls for 40:1, and the carb is set for 40:1 creates a condition of not enough fuel per volume of air. The oil is displacing the fuel. The incoming fuel/air charge cools the cylinder/piston - not the oil! Sure, the oil lubes the cylinder walls, but what good is that going to do when it is so hot in there, from a lean condition, that it just burns off? It's not going to do any good = lean siezure. I could :deadhorse: until I am exhausted, and there will still be people who think 16:1 is better. Well, if it works for you, continue wasting oil and go for it! OR, adjust your carb properly, run 40:1 and be done with it.

 

[alderman]

stoichiometric burn?

Help me out on this. I haven't found it in any of my Shindaiwa manuals.

 

[Elmore]

Uhh...yeah...

Stoichiometric Combustion
Stoichiometric or Theoretical Combustion is the ideal combustion process during which a fuel is burned completely.
http://www.taftan.com/thermodynamics/COMBUST.HTM

Combustion Stoichiometric Ratio
The lambda is the ratio of air divided to fuel, divided by the stoichiometric ratio.
The stoichiometric ratio is the ideal ratio. If the lambda is high, there is more air than fuel, which leads to inefficiency and NOx. If the lambda is low, there is more fuel than air, which leads to CO and non-combusted fuel going through.
http://mainland.cctt.org/istf2002/background/engines.asp