what kind of number rating on race fuel

T

Tuff

Member
Aug 17, 2004
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Hey guys, what i was wanting to ask is what kind of number rating on fuel should i run with a 240 big bore kit on my kdx 200. I mean 93 or above would be the best..and is this a hassle to get the fuel!

thanks to all!
 

IndyMX

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Joburble said:
My understanding is that you always run the highest octane fuel you can get.
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Which would be a waste of money..

My understanding is you run the lowest octane your bike will run with without knocking. Otherwise you are spending money on higher priced fuel for no reason.

Unless that fuel has other properties that you require.

If you aren't racing and somewhat seriously, you can get away with decent pump fuel.

I run Amoco Ultimate in my bikes, and haven't had any performance issues.

I have run cheaper pump fuels, but the Amoco Ultimate seems to be quite a bit cleaner running than most other pump fuels I have seen around here.
 
J

_JOE_

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May 10, 2007
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It's not going to hurt anything to go over the required octane though you can cause some engine damage by going too low.

If you can afford it a 2 stroke bike specific fuel would be best for many more reasons than just octane rating.
 
T

Tuff

Member
Aug 17, 2004
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What do you mean by specific fuel? Like what ever compression im running go with fuel that is designated for that. IM not sure what your saying.

thanks cyrus
 

Joburble

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IndyMX said:
My understanding is you run the lowest octane your bike will run with without knocking.
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That actually made me laugh. That's like saying I'm gonna eat the crapiest food I can eat with out getting sick. Same deal with the bike. Sorry Indy I'm not with you on that one as find it a poor philosophy. Cheapest oil I can run without it seizing, cheapest tie downs I can buy without them snapping, etc etc.
I am not saying you do those things, but rather as a philosophy I think to treat your bike the best you can and it will treat you the same way. That's how I roll :cool:
 

ellandoh

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IndyMX said:
Which would be a waste of money..

My understanding is you run the lowest octane your bike will run with without knocking.
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thats my understanding too :cool:

find the fuel you need and jet for it and stick with it.
octane suppresses spark knock and will not make your bike faster or safer unless you have a tendency to run hot. i.e covering the rads or cooling fins with mud and need some spark knock safety buffer

i personally go for the guy who has 93 octane with the least amount of ties to hugo chavez
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Running high octane race gas will not gain you vast horsepower increase across the board, matter of fact, none at all. What it will do is when properly jetted, increase throttle response. If its a decent race fuel for dirt bikes! Some high octane race fuels can destroy your engine. Specific for what you need, there are a lot of different types of race fuel. Unless you are suffering detonation from higher compression, you do not need high octane race gas. I have always went to a busy Amoco or Shell station for premium fuel, or when I really need it, Firepower race fuel. Trail bikes could probably run on regular gas, or kerosene for that matter. I will guarantee most premium fuels will respond better than that. Vintage Bob
 

IndyMX

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As long as the engine isn't knocking, for the majority of us weekend warriors (non-racer types) anything more than that isn't doing us any favors, and isn't doing us any harm.

I would never suggest running the worst pump fuel you can find, and I didn't suggest that above.

If it happens that your bike requires 110 octane race gas, then by all means. However, most bone stock motocross bikes will run just fine on 93 octane pump gas. I believe that's that the manufacturer recommends.

If I were to go out and buy 5 gallon containers of VP race gas just to do the little bit of riding that I do on the weekends, it would be a colossal waste of money.

I'm sure a lot of the wiser minds around here would agree.

If you choose to spend the extra money on fuel that you don't need, no one is saying you shouldn't.
 

Joburble

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Fair enough Indy. Here in New Zealand we can easily buy 91, 95 and 98 octane. I tried 91 octane a couple of times years ago in my XR600 and it knocked like a dog when I had it pinned to the stopper. Prior to that I always used the highest octane I could find and since then I have too. Every one I know and have heard of in this country runs the highest they can find and some people I knew used to run 100 octane aviation gas. Personally I will stick to the highest octane I can find as it's only a few cents more expensive. Also I think we may have different additives in our gas that don't apply in the US, so having said that I think I will refrain from commenting on gas issues in other countries in the future because what applies here may not apply there.
 
P

Porkchop

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Apr 27, 2001
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Chevron , Shell, or Unocal 76, 93 pump premium with some Pennzoil outlaw octane booster added to it, has served me well for many years.
:ride:
 

whenfoxforks-ruled

Old MX Racer
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Porkchop said:
Chevron , Shell, or Unocal 76, 93 pump premium with some Pennzoil outlaw octane booster added to it, has served me well for many years.
:ride:
Click to expand...
Everything but the seemingly miracle in a bottle. Nothing more than an old wives tale, nada senior! Vintage Bob
 

IndyMX

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Joburble said:
Also I think we may have different additives in our gas that don't apply in the US, so having said that I think I will refrain from commenting on gas issues in other countries in the future because what applies here may not apply there.
Click to expand...


From what I've read on here, they use different additive packages in different areas of the country here, and different package from summer to winter. So I wouldn't be at all surprised to know that they use a different package there.

I'd even venture to guess that they don't rate the octane in the exact same way either.
 
J

_JOE_

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Fuels blended for your application will burn much cleaner. You'll have less power valve gunk, cleaner combustion chamber and silencer packing should last longer. It's easier to jet and does provide better throttle response.
 
P

Porkchop

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Hey V- Bob, the pennzoil stuff is just an easier way to get a shot of toluene in my fuel without the epa paperwork associated with buying it by the gallon. The difference between winter blend/ summer blend can cause my ride to ping, when dealing with heat & large elevation changes during a ride. Wives tale or not, I've had good luck with it. :cool:
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Joburble said:
I bet 'Tuff' is confused now :ohmy:. Sorry Tuff.
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Who? Kidding aside. Look into the archives. There was a guy who went to the paint store, toluene is cheap, and he thought it worked great. Throttle response, he could hold it wide open, and light a smoke before the revs caught up, imo? Thank someone none of the dolts have been around lately with the aviation fuel again! Vintage Bob
 
T

Tuff

Member
Aug 17, 2004
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well, sorta..he went from good to way out in left field beyond the corn stalks. but hey...its alright no biggie! but hey ..do you all think 93 octane would hurt a 240 cc cylinder.
 
J

_JOE_

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Unless the compression ratio is jacked way up you should be fine. Just ask whoever does/did it. They will know what the fuel requirements will be.
 
M

mudpack

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Nov 13, 2008
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Joburble said:
I tried 91 octane a couple of times years ago in my XR600 and it knocked like a dog when I had it pinned to the stopper.
Click to expand...
The XR600 has very different octane requirements than a KDX200/240. For one, it is a fourstroke and does not enjoy the knock suppression qualities of premix that a twostroke does. For another, the huge bore of the 600 is far more prone to detonation than the small KDX. Lastly, even in the XR600, you only need the lowest octane rating that will allow you to operate without detonation, no matter what that octane rating might be. High octane/high priced fuel is not "better" for your engine than fuel with just adequate octane rating....in fact, your engine doesn't even know it.
High octane fuel is simply fuel that is harder to ignite than lower octane fuel. :cool:

IndyMX said:
My understanding is you run the lowest octane your bike will run with without knocking. Otherwise you are spending money on higher priced fuel for no reason.
Click to expand...
IndyMX is quite right.
 

Joburble

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Interesting. If higher octane is harder to ignite it must change the burn timing, hence the knock of low octane as it is too advanced, makes sense.

If that's the case in theory you could retard your timing and run lower octane fuel. Unless it pre-ignites on its own without a spark.
 
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whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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There is a guy, actually a Doctor. He works with the Phillips bp research, racing, anything with an engine. Believe it or not, he enjoys talking 2 stroke MX race bikes. And if I ever get the money for his management and sensor systems???? But, he developed a numbering system for pure race fuel. WARNING: Talk to Dr Dave before trying to use it! Tell him what you are doing, he will tell you what you need. Some fuel does not have enough piston cooling characteristics, even though its a type of 2 stroke race fuel, not for MX! The Xamax oils and Race Kool are unprecedented quality also. Take the fuel quiz! Vintage Bob , http://www.precisionautoresearch.com/RACING_CHEMISTRY/PAR14.htm
 

Joburble

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Doh! I was wrong in my initial response to the post about going for the highest octane you can get (there is a first time for everything :) ). Sorry IndyMX for my comments about me laughing, I was wrong (although I did laugh it was out of ignorance).
 

IndyMX

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No worries.. Education is a good thing.
 
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