What fuel you guys running?

[mnovarossi]

After 2 months of not riding, I finally have my rebuilt motor back in the frame again! According to the guy that rebuilt it, detonation was the cause of death. I always used pump gas (92 or 93 octane). He told me I should be ok with pump gas from a high traffic gas station but i dont know if its worth the risk now. What fuels are you guys using? I can get 100 octane(leaded) from the local airport for about $3/ gallon. Think it would work ok? ?

[grayracer513]

I run pump gas.

AvGas is not a good idea, although we used to run it in the really high compression BSAs we ran back in the day. Your engine was built to run unleaded fuel, which is naturally cleaner than leaded as far as what it leaves in the engine and on your spark plug.

If your bike is at the stock compression ratio, it should run fine without the extra octane. A cheap way out if it shows a tendency to ping is to use a GOOD octane booster from a performance parts outlet. I don't trust the cheap ones from the budget auto stores. Even then, because of the possiblity of the chemicals in the booster damging carb components, you'd be on your own.

True detonation is extremely rare, and I would be surprised if that was actually what happened. Fuel is supposed to be ignited at a single point (multi-plug engines are an exception) and the flame is supposed to spread outward like a wave. It's supposed to burn, not explode. Detonation is when all or a large portion of the fuel in the cylinder ignites and burns at the same instant. It is very destructive and can't be tolerated for any significant amount of time.

Pinging can cause damage, too, just not as fast. Pinging occurs when one of the following things happens. The gas burned too quickly, as with too low an octane. The gas "pre-ignites", or ignites too soon, caused by incorrect timing, or something in the combustion chamber hot enough toset it off before the spark does. Or, overheating. In this case, the burn starts normally, but as combustion pressures rise, the combination of heat and pressure cause the fuel to burn too rapidly at the end of the burn.

Something that could cause this is disconnecting the TPS. This removes the ability of the ignition module to create a 3-D timing map (advance/rpm/throttle load) and reduces it to the old fashioned advance based on rpm only. It seems likely to produce too much ignition advance at high throttle/middle rpm condtions.

Try a good pump premium first. If it pings you should be able to hear it. If it detonates, will certainly hear it, probably even feel it.

[yz426onNOS]

Klotz race fuel

[Smegol]

96 or 98, depending on which service station I go do. I prefer the BP Ultimate, or Mobil Synergy 8000 (not to sure if you get that over in the states) both 98 octane. But buying from low volume service stations can be a bit dangerous; recently I had a friend who ended up having to replace the injectors and a whole heap of other parts in his Misubishi Legnum due to bad gas from a very rural service station. I've also run the Elf race gas, and noticed no difference between that and the BP Ultimate in the thumper.

[Ga426owner]

What is the bike?

I only run VP Ulimate4 in my 450....with nothing but great results. ?

But, get your wallet

out

[RJB]

Shell V-Power works fine for me, but then I don't race.

[noslo98]

VP Ultimate 4 mixed 50% with prem 76 best fuel out there.

[Jeffro426]

Mixing pure virgin race fuel with pump unleaded is like mixing a fine wine with coolaid...pretty much defeats the purpose of using race fuel. I for one, run premium pump gas and if the bike needs it(as in its pinging) ill give it straight VP110 or whatever else is handy.

[noslo98]

the bike runs the same mixed as it does with straight u4 and runs like [@#$%&*!] with c12 pre detonates.

[SSpeeDEMONSS]

what is the octane rating for VP ultimate 4? also, how much does it cost per gallon?

[Ga426owner]

what is the octane rating for VP ultimate 4? also, how much does it cost per gallon?

do a search - this has been hammered to death - Octane is not the key issue....VP is probably 92-94 octane - it is highly oxyginated - cost 5-10 dollars per gallon ........ And do not mix this with premium....that's like peeing in your drinking well..... ?

[Jeffro426]

the bike runs the same mixed as it does with straight u4 and runs like [@#$%&*!] with c12 pre detonates.

Then its either not stock or not jetted properly...what have you done to the motor?

[noslo98]

the bike has jardine rt-4 full system and has been jetted by local shop 185 main 50 pilot they told me to mix it. I was thinking of trying it straight next time. When I first ran U4 the bike ran the same straight as it did mixed so thats why i have been mixing it scince.

[mnovarossi]

Oh yea, the bike is a 2000 yz426. I never heard the bike ping or knock, but it makes so much noise normally it would be hard to hear anything abnormal. The guy that rebuilt it is an expert with mx engines so I figure he knows best when he tells me it was detonation that caused it to, umm, expire. Whatever the cause, it is now fixed, (Finally) and I can ride once again! I guess I'll try pump gas again, and see what happens. Thanks for the replies.

[Jeffro426]

So its a stock motor and your getting detonation? Do you even know what detonation is??? ? If your bike isnt running right on straight pump gas or even c12 for that matter, with a stock motor, youve got problems elsewhere. Glad your happy with your U4 though...just think its beyond pointless to run it mixed...but to each is own!

[gonzo]

the bike runs the same mixed as it does with straight u4 and runs like [@#$%&*!] with c12 pre detonates.

Why are you running 112 Octane gas? You couldn't possibly be getting detonation with octane that high. That's your first problem. The second is a 50 pilot. Unless its -276 degrees Kelvin (only other dorks will know this) outside you don't need that. No bigger than a 45 is neccessary. Just run straight U4 with 2 bigger main jets, 45 pilot, and go down 1 tick on the needle. You can mix U4 with premium gas but every bit you mix just decreases the potency that much. Then again I wouldn't mind have a 3% gain for twice as long as a the 6% gain at the same price.

[yzf_rider400]

I run whatever's the highest octane at the gas station I'm at. Usually a 91 octane or above. My engine doesn't ping and I've been riding with it for a few years with no problems. I don't race and the bike runs fine so I say screw it, why not?

[noslo98]

I am running this jetting because the bike ran like crap after i installed the exhaust. So i took it to the yam dealer and had them put it on the gas tester to see where i was at and that us how I ended up with a 50 pilot and a 185 main. I have a friend that dynoed his bike with u4 mixed and straight and the diference was minimal so i dont see the point in running it straight when you can make 10 gallons out of one can when the bike runs pretty mutch the same.I have alwaise ran race gas in my bikes for consistancy reasons i may not need it but i am going to run it no matter what. I would never run straight pump gas in my bike but if you want to put the garden hose in your $8000.00 bike go right ahead.

[yzf_rider400]

I'm going to try the garden hose next time I ride. If the pump gas is working good why not dilute it with some water and save a few bucks. ?

[Jeffro426]

I have a friend that dynoed his bike with u4 mixed and straight and the diference was minimal so i dont see the point in running it straight when you can make 10 gallons out of one can when the bike runs pretty mutch the same.I have alwaise ran race gas in my bikes for consistancy reasons i may not need it but i am going to run it no matter what.

Your totally contradicting yourself there...you say you run race fuel for consistancy reasons...well, as soon as you pour a drop of that pump gas in it, you shot your consistancy to hell. The only reason i could ever see anyone ever wanting to run race/pump gas mixed would be for extra octane if detonation was a problem but not enough to justify straight race fuel. ?

I would never run straight pump gas in my bike but if you want to put the garden hose in your $8000.00 bike go right ahead.

God forbid you put in the tank what the bike was designed to run on!