Fuel mixture

Blaster_faster

New Member
Nov 24, 2011
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yelm wa
i just put a oil block off kit on my blaster what would be a good mixture? i want a little more power but i dont want to harm my engine. stock muffler and jetting
 
32:1 is fine and is what most people on here run. 8oz of yamalube for every two gallons of gas.
 
32:1 is the most common ratio unless the maker of the oil you use states differently.

I am prolly going to kick a bees nest, but to get a little more power I premix at 25:1, which is said to raise the compression a tad due to the extra oil.

I use a castor based oil "Maxima 927".

If running at 25:1 you will need to increase the size of the main jet by one size as the extra oil leans the fuel out some.

I also use 98 octane fuel.

I also have the timing an extra 4 deg in advance to increase the low/mid range, this mod will loose a little top end.

If you want lots more power swap the pipe for an aftermarket one, and rejet accordingly,,,, but not a DG.
 
To help cut down any confusion here.

There are two different type of mixtures when you are premixing your gasoline and oil. You have the oil mixture (generally 32:1) and then you have the air/fuel mixture (main jet size)

Blaaster, oil ratio is a personal preference. Some believe it does help power to have more oil in there but the fact is, more than is required to maintain an oil film for the piston skirts and crank bearing surfaces is just being wasted. You're fouling plugs a little quicker and possibly sooting up the works a little more than necessary.

Air/fuel ratio however is NOT a personal preference. That is demanded by the particular engine. That's what a "plug chop" is all about, determining your engines fuel requirements. A lean engine puts out more power but for a much shorter amount of time. Lean engine's run much hotter and as a result are closer to predetonation and loss of the oil film.
 
Some believe it does help power to have more oil in there but the fact is, more than is required to maintain an oil film for the piston skirts and crank bearing surfaces is just being wasted. You're fouling plugs a little quicker and possibly sooting up the works a little more than necessary.

To kick the nest again. And I am not advocating that any one runs a fuel/oil ratio other than their personal preference. I am just stating what works for me.

The extra oil is to help the rings do a better job by stopping excess blowby.

Also to give me peace of mind that the motor is getting the correct amount of lubrication it was designed to run on.

I have been riding 2 strokes for over 50 years and can count on one hand the amount of plugs I have fouled and ports I have cleaned from using that little extra insurance of a little more oil.

In my way of thinking a correctly jetted motor, ridden hard, with that very little extra oil, is going perform better, and last so much longer between rebuilds.
 
http://www.blasterforum.com/engine-13/pre-mix-ratios-myth-facts-read-14935/ If you read this you can make your own informed decision. My son and I run the Blasturd and Banshee both @ 28:1.

IIrc from reading this, the smaller the size the more oil. My 250 Elsinore was either 16:1 or 20:1 can't remember. When I finally tore it down after countless hours the bore was still well within specs, only ever used Castrol R bean (no longer avail).
 
32:1 on amsoil dominator and I cant complain cause it's premium stuff anyway. Generally my buddies rule of thumb is 32:1 with iffy stuff and 40:1 with the good stuff. Like i said above I play it safe with amsoil at 32:1 cause it's good stuff and cheap where i live.
 
32:1 here! Super M! I did use 28:1 once but only cause that's all that was left in the bottle at that time, didn't notice any difference.
 
i am new to all of this and dont want to hurt my bike, i was wondering what type of yamalube to put in my fuel
 
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The quart size Yamalube bottles will have a blue Banshee on the front.

On extra oil... I don't recall ever seeing 2-stroke engine failure that was a result of too much oil in the premix. It will contribute to fouling plugs, but that doesn't mean that simply going to a richer premix will absolutely result in fouled plugs, only that it can. I ran the same plugs in my Banshee for 4 years, the first two of which were ran at 24:1, then 32:1, and 40:1 for the past 6 months.

Also, if you think that you may run gas with ethanol at some point, jet according to the gas with ethanol now. At 10% ethanol, you'll require 4% more fuel than mogas in order to maintain the proper stoichiometric ratio for that fuel blend. Top that off with the difference the fuel content per volume between 40:1 and 24:1 (1.4% leaner), and you're now running 5.5% less fuel that you need. That's enough to go from an AFR of 13:1 to 13.7:1, which I call significant. If you add to that the increased viscosity of the richer premix, which flows less through your jets, and the situation is worsened in a multiplicative fashion. If you jet for 93w/eth, you'll be rich when going to mogas = good to go.

Of course, you can figure all of this out and know why you need larger jets, but in the end, you're going to need larger jets. Effectively, nothing has changed on the practical side once you choose your fuel and oil choice; you still need to jet and plug chop either way.

I will say this though: I've seen cars that were tuned on 93w/eth that threw knock codes when running mogas. The simple reason for this is that ethanol has higher detonation resistance. This is negligible, but it does exist. 93 with 10% ethanol is roughly equivalent to running 95 octane (again, negligible).

Side note - I spoke with a tuner some time ago and he told me that pure ethanol is capable of roughly making the same power as 116 octane.
 
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In a nutshell, if you add more oil to the fuel you will need to increase the size of the jets to compensate for the leaner AFR.

Changing from 32:1 to 25:1 leans out the fuel ratio approximately one size main jet.

It is possible to run 16:1 in a 200cc engine without fouling a plug, but jetting must be changed to suit the lack of fuel in the mix.
 
In a nutshell, if you add more oil to the fuel you will need to increase the size of the jets to compensate for the leaner AFR.

Changing from 32:1 to 25:1 leans out the fuel ratio approximately one size main jet.

It is possible to run 16:1 in a 200cc engine without fouling a plug, but jetting must be changed to suit the lack of fuel in the mix.
Blaaster I can tell that you have much knowledge in two strokes I recently rebuilt my 99 blaster .02 over with pistonI have a 3/8 inch Reed spacer and a FMF pipe I am currently at a 260 jet but it still seems to sputter when it hits the powerband and the plug still seems to be a bit light in color should I increase the jet size maybe one to two sizes upI am relatively new to working on two strokes myself any info would help Thanks again