Premix

[savage sausage]

Dumb person alert !!
let me start off by saying math is not my strongpoint at all.

I stupidly mixed 10 litres of gas @ 30.1 , but should have mixed @ 40.1 how much gas do i need to add to put it right at 40.1

 

[Jacob 'Berg]

Dumb person alert !!
let me start off by saying math is not my strongpoint at all.

I stupidly mixed 10 litres of gas @ 30.1 , but should have mixed @ 40.1 how much gas do i need to add to put it right at 40.1

I would just run the 30:1. A little extra oil will not create an issue, other than a little more smoke.

 

[savage sausage]

just worried it'll foul the plug

 

[RBrider]

Using US gallons, that works out to about 1 oz of oil per 4 liters of fuel or less than 1 oz per US gal.

Like JB, I'd just run it.

RB

 

[savage sausage]

ok will do, thanks

 

[pscook]

Add 3.3 liters of gas to your premix to get to 40:1.

30:1 = 10 l gas + .333 l oil
40:1 = 10 l gas + .250 l oil
40:1 = 13.3 l gas + .333 l oil

I reverse engineered from this website:
http://www.csgnetwork.com/oilfuelcalc.html

 

[motopsycho87]

It won't foul the plug unless you are jetted rich. I always run mine at 30:1 (more oil is only a good thing!), with correct jetting I get no spooge, barely any carbon deposits, and haven't changed my spark plug in over a year of riding almost every weekend.

 

[Zman]

30:1 is actually a slightly leaner air fuel mixture than 40:1 because there is less fuel in the mix.

 

[gasgasman]

30:1 is actually a slightly leaner air fuel mixture than 40:1 because there is less fuel in the mix.

Correct.

The viscosity of the 30:1 mix is heavier than the 40:1.
In simple terms, less fuel through the jets with the 30:1 mix.
You can fine tune your jetting by altering you fuel/oil ratios.

 

[(F5)]

Just buy one of these. Never have to calculate again, just turn to the side that says 40:1 and fill to the level of gas you want. Simples.

http://m.ebay.ca/itm/Apico-Oil-Measure-Jug-Tube-500ml-Max-Motorcycle-2-stroke-Mixing-Container-/251635687160?nav=SEARCH

 

[Cox76y]

I downloaded an app from google play. It makes it easy. You choose the ratio and input the amount of fuel n it tells you how much oil to mix.

 

[motopsycho87]

Correct.

The viscosity of the 30:1 mix is heavier than the 40:1.
In simple terms, less fuel through the jets with the 30:1 mix.
You can fine tune your jetting by altering you fuel/oil ratios.

I was sad enough to actually calculate this. The difference from 25:1 to 50:1 isn't even a jet size, and unless it's an incredibly dense oil, viscosity only changes by a fraction of a centistoke.

 

[3beejay3]

This is one of the reasons why the metric system is so much easier to use than the wonky US system.

Oil/Gas calculations are a snap.

 

[motopsycho87]

But everybody forgets to add the mix to the fuel amount calculation to get it accurate...

I put 30ml in a litre of fuel.
30/1000=33.333'

But really it's,
30/1030=34.333'

 

[Zman]

Correct.

The viscosity of the 30:1 mix is heavier than the 40:1.
In simple terms, less fuel through the jets with the 30:1 mix.
You can fine tune your jetting by altering you fuel/oil ratios.

I agree that the viscosity is increased for 30:1 vs 40:1 and additionally there is less gasoline in the mixture per part air because the extra oil replaces fuel. The oil does not burn with the same energy content as the gas (if it burns at all, but that is a different conversation).

 

[3beejay3]

Curious;

Are all you guys running high level MX or WFO desert such that you need so much oil?

I'm mostly in the woods & have only ever run 50 or 60:1 full synthetic, with really good results. I also don't fuss about fuel either & just run whatever cheap stuff happens to be nearby.
I'm not the fastest rider, but not the slowest either.

Only time I've had an issue with a plug is the stock one that only lasted about 5 hours, when it crapped out. The second plug lasted over 200 hrs and only got changed cause I did a top end that, it turned out, didn't need to be done for another 100 hours or so. (there's a thread around here somewhere about that)

30:1 or 40:1 seems like a lot of oil if the bike is only in the woods much of the time.......

 

[barossi73]

I came across a study somewhere that showed more oil in the mix gave a very slight hp increase due to increased sealing of rings in bore.ie.slightly better compression.the trade off is increased chance of plug fouling.fwiw i run 40:1 but only because thats the oil manufacturers recommendation on the bottle.for the record iv never found any noticeable change in spooge from running different ratios-less oil does not mean less spooge.jetting changes and oils of differing flashpoints will affect spooge though.different oils can change plug colour and/or leave residue on the plug also.(and smell different!)

 

[motopsycho87]

Never fouled a plug at my current mix. The study you're talking about is from the graham bell book, and it was using castor oil, there is at least 4 pages where he talks about people using lean ratios with fully synthetic oil and how people brag about it as if it's a power enhancing achievement. Synthetic oil lubricates better yes, but it also cleans better etc too. But the oil also has to be present in order to achieve this.

And my bike gets thrashed to death. Why would you buy a 2 stroke if you weren't going to open the throttle?

 

[Zman]

I change oil ratios and oils depending on the riding I will be doing. I use more oil when I am riding harder. Similarly I use Klotz R50 when I am riding harder and use the Techniplate when trail riding. The R50 has a much higher flash point and tends to spooge if you are not on the pipe.

I have not had a problem switching between these oils even in the same tank of gas. I do mix premix in a gas can and the two premix fuel seem to blend fine in the tank.

 

[eff]

Amsoil Dominator at 50:1 all the time. Amsoil makes my bike run incredible and you can feel a noticeable HP increase.

My buddy didn't believe me until he tried it and was sold as well.

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