Fuel?

[arnie230]

I am new to the 4 stroke world and I am wondering what fuel to run in my new '06 yz450F? Do I have to run high dollar race gas?? I have been a 2 stroke guy 4ever and need some advice....Thanks!!!!!!

[450_rider]

All you need is good fresh premium fuel.

[flintlock28]

Yep, what 450 rider said....

Motocross Action magazine recommends 91 Octane to about 94 octane (R+M)/2 method.

The (R+M)/2 method is the typical method you'll find on U.S. gas pumps. THe only time you'll need to run higher octane, is only if you change over to a high compression Piston.

[TexN343]

What is the disadvantage from from regular unleaded? I'm thinking it's 87 octane?

[barch88]

My front fender sticker, and manual says "Premium Unleaded Only" so that is what I run.

[quailboy]

cheaper gas will give you worse performance and will dirty your carbs. its best to run the best fuel and oil that you can afford. makes things last longer

[flintlock28]

At 87 Octane, you may experience detonation (Ping).

Short term, a mild amount won't hurt anything, but if you get detonation over a long period of time, you're going to damage your Engine. Ping is caused when the Piston is still coming up, and the fuel is prematurely igniting, trying to ram the Piston back down as it's still moving up....NOT good!! Higher octane fuel (say 91) won't prematurely ignite as easy as 87, thus no Ping.

The manual for my 04' Yz450f calls for 95 RESEARCH OCTANE (which translates to 91 octane (R+M)/2 method) Use 91 minimum for a STOCK engine.

[450_rider]

So is ping kind of like your engine acting like a diesel

[YZ117]

AVGAS for sure!

[flintlock28]

Yes, Ping is similar to a diesel since compression is firing off the fuel.

What is happening is that as the Piston is going up, it is generating heat as it compresses the fuel/air mixture, and unfortunately it is igniting the fuel/air mixture before the piston reaches TDC (top dead center), even before the spark plug fires.

Just imagine the kind of force that piston is encountering as it's making it's way up, and getting slammed by the pre-maturely lit fuel/air mixture!!! Yikes, Not Good!! Eventually, you're gonna get piston damage. Every engine is designed to use a certain Octane Rating which is nothing more than a rating to prevent ping (a certain value).

With these typical 4 strokes (Honda, Yamaha, Kawisaki, etc.) they are designed to use about 91 Octane. If you go lower then this value, than it means the fuel will be more prone to ignite too early (ping), thus subjecting your Piston to a downward "push" as it's still coming up. As long as you meet the Octane value rating by the Engine designers you'll be o.k.

You can use higher than required Octane (let's just say you use 100 octane for your bike) and that will be fine, But why spend more money for a higher priced fuel that won't result in any more power???? Remember, Octane Rating is nothing more than a rating for preventing 'Ping" or "knock", it has nothing to do with Cleanliness of Fuel, or

Quality of Fuel, or energy content. People seem to mix this up all the time.

So on a STOCK bike, just use 91 octane or slightly more.......I usually use BP 93, since it's common around here. If you switch to a Higher compression Piston than STOCK, THAN you will have to up the Octane rating because know you have increased the cylinder compression, and that 91 octane fuel will probably pre-ignite (ping) with the higher compression.

hope this helps.

Don

[flintlock28]

AVGAS is another INCORRECT fuel to use....

I don't feel like posting all the reasons why....but let's just say that AVGAS is designed to be used by Airplanes running at much higher Altitudes, at nearly CONSTANT RPM's. HOW MANY OF US RIDE OUR MX/OFFROAD BIKES AT NEARLY THE SAME RPM'S???? it is basically a proprietary fuel, designed for the narrower applications of Airplanes. Plus it costs quite a bit more money.....

A number of the MX magazines, stated the same things and said "Don't use it"

[YZ117]

I was just kidding.

[arnie230]

I had to ask as the manual recommends 95 octane or higher. I wonder when Sunoco stopped selling there 94 fuel?

[barch88]

I had to ask as the manual recommends 95 octane or higher. I wonder when Sunoco stopped selling there 94 fuel?

I thought it recommended 91 or higher...not 95.

[jamiehughes]

i run the race gas in mine and it seems to make it not pop so much on hard deceleration,when its real warm outside. seems to make the bike run a little cooler.

[ncmountainman]

i run the race gas in mine and it seems to make it not pop so much on hard deceleration,when its real warm outside. seems to make the bike run a little cooler.

thats because higher octane fuel will genarally make your bike run richer,one good thing about race fuel is that it is usually more consistant than pump fuel,pump fuel actually changes content seasonally and regionally ?

[Desert Rat 450]

Yep, what 450 rider said....

Motocross Action magazine recommends 91 Octane to about 94 octane (R+M)/2 method.

The (R+M)/2 method is the typical method you'll find on U.S. gas pumps. THe only time you'll need to run higher octane, is only if you change over to a high compression Piston.

? enough said.

[Ga426owner]

AVGAS for sure!

a big no no................ ?

use premium unleaded or use VPU4

VPU4 is expensive but adds 2-3hp and burns much cleaner than pump gas. I use this exclusively

[Daffy Duck]

What is the disadvantage from from regular unleaded? I'm thinking it's 87 octane?

I think low octane petrol can cause pre-ignition which means the petrol air mix explodes before it should. This is bad in a car (knocking) but it is really bad in a high compression aluminium engine..

[grayracer513]

flintlock, you're almost entirely correct. Good job. ? But there is a fundamental difference between detonation in a gas engine and compression ignition in a diesel, or in a gas engine, for that matter.

In a diesel, even though the fuel is ignited by the heat of compression, the fuel burns over a period of time as it is injected into the cylinder, not all at once. In an old, carboned up gasoline V8, you can have a condition under which the heat of compression can cause a hoe spot in the carbon to glow and ignite the fuel, but it still burns outward in a wave from that point.

But Detonation, whether it is the partial detonation of the last bit of the fuel charge that you hear as pinging, or serious early detonation, is the instantaneous combustion of all the remaining fuel in the combustion chamber, all at the same time. It is extremely dangerous. Rocks in the cylinder would actually better for the engine.

Arnie, the manual says 95, but that is Research Octane, which is generally about 5-8 points higher than the Motor Octane number for the same fuel. U.S. gas pumps are marked with the average of both of these (shown as (R+M)/2, as was mentioned), so 91 at the pump is the equivalent of 95 research, or even higher.

Race fuels change the jetting requirements for reasons related to fuel chemistry, not their octane rating. Some high and low octane fuels behave differently for the same reason, but the octane rating itself tells you ONLY how resistant to compression detonation the fuel is, and nothing whatsoever else.