Bike Problem or Bad Fuel?

[Tim Mainard]

I ran my 954 last weekend at the track. I put racing fuel in it from the track and it ran really bad.  It shugged and sputtered on and off.  I took it to the dealership and it tested out fine, no problems.  They said it might have been the fuel. It has about 1800 miles on it and is all stock. Has anyone had similiar problems with fuel injected bike?

[sportbikepete]

When you switch to race fuel without and carb/fi changes of course you may have problems. You know race fuel is also leaded right? Think about modern cars, if you run Super in them they run like crap because the computer FI is set up for a max octane of say 87 and you put in 93. Now on your bike it may be set to handle 94 octane and you put 111 in it you will have problems.

[TBMain]

Thanks for your input. I didn't specify in my first post, but I did run 100 octane unleaded race fuel. I know better than to run leaded in a bike that requires unleaded only. Sorry for the lack of info.

[tcchin]

Octane ratings are not something for which a fuel delivery system is tuned, as they don't affect the air/fuel ratio. Switching between 87 and 93 octane pump gas in any stock production vehicle that's designed for 87 octane should be completely seamless. If anything, the higher octane might allow the knock sensor some time off and let the ignition run slightly more advanced, thus improving throttle response. Also, the additive packages in the 93 octane fuels may also yield slightly higher energy densities in the fuel, allowing slightly higher output and better fuel economy.

I'm not sure which brand of fuel you were using, and what the condition of the fuel itself was, but if the fuel was stale, or if its physical and chemical properties differed significantly from pump gas, then I can understand how you would have problems. However, if the fuel was fresh and it was something like VP Performance Unleaded or 76 Unleaded Racing Fuel which are both oxygenated, 100 octane, unleaded fuels, then I would be surprised that your bike noticed a difference.

[Xian_13]

 ??? Hum...
When it comes to gas, it seems that there are alot of people that only know half the story... I am sure I am one of them.

Octane rating... This is the rating given to the gas based off of its combustion factor. Meaning the high the octane, the less chance of it firing with out ignition. (desieling).

High compression motors need high Octane. Piston knocking is pre-ignition of the gas, Lower Octane gasses ignite before they are meant to.

The wrong octane. If your motor is engineered to run 95 octane, you should NOT run less then 95. The compression will ignite lower octane fuels before ignition. If you run to high of octane, you have nothing to worry about. However... Higher octane fuels will hurt your proformance. I have seen the dyno results (no rejetting) from pump 97 to race 110.

If you lean out your motor (lean is faster, but runs hotter) you can gain HP, but if you are getting things to hot, you will cause the desieling effect (knocking, and under racing conditions, a blown motor). If you are jetted to run pump gas, and you are not lean , higher octane will hurt HP. High octane may cause a Fat effect.
Though I may be miss informed, but these are things I have seen off of the dyno.

[tcchin]

Knock is the sound of the piston rattling in the bore as the multiple flamefronts caused by detonation collide. Pre-ignition is silent.

Race fuels produce less power than pump gas if they are not oxygenated. Union 76 Super has produced three more peak horsepower than VP C12 on back-to-back dyno runs on a stock GSX-R600 because of its oxygen content. However, many of the oxygenated fuels become unstable in high-temperature conditions (Pike's Peak, Las Vegas, Phoenix, Willow Springs, Texas, etc.), and you need a more traditional fuel to keep your motor together.

Leaner is not faster. Stoichiometric mixtures are only efficient in theory. In fact, optimum power is achieved somewhere between 12.2:1 and 11.8:1, depending on the motor, the fuel and the atmosphere.

If you are jetted to run pump gas, then your jetting would be way too rich to run non-oxygenated race gas. Oxygenated race gas (Special 5, MR1, etc.) would probaly be a closer match. This has nothing to do with octane ratings and everything to do with oxygen percentages.

[pmoravek]

Huh?

[unforgivenracing]

I'm going to stay away from the gas issue and ask you something towards the other.
 Did you change the pipes on the bike?

Being that you have Fi, It could be the problem.
  If so, Try disconnecting the battery, wait a while, reconnect, and run the bike (with the desired fuel of your choice) for about 125miles.
This will reboot the memorie and allow the computer to recal the fuel setting via the new reading it receives without it thinking there is a problem it is trying to fix.  It is a computer after all. this trick works for other things too.

[Litespeed]

Getting bad race gas is a common thing at tracks.  It used to happen about every other outing to at least one of my friends when I was drag racing.  Getting bad gas from the local station isn't as likely because they run through it so quickly.  IF your bike doesn't need the octane don't buy it.  If your bike does need the octane, make sure you get it from a reliable source in a sealed container.

[TZ_Boy]

I'm going to stay away from the gas issue and ask you something towards the other.
 Did you change the pipes on the bike?

Being that you have Fi, It could be the problem.
  If so, Try disconnecting the battery, wait a while, reconnect, and run the bike (with the desired fuel of your choice) for about 125miles.
This will reboot the memorie and allow the computer to recal the fuel setting via the new reading it receives without it thinking there is a problem it is trying to fix.  It is a computer after all. this trick works for other things too.

Sounds good except  the computer does not have memory, or different fuel settings, is unable to take readings, and is helpless to fix itself.

[TZ_Boy]

Thanks for your input. I didn't specify in my first post, but I did run 100 octane unleaded race fuel. I know better than to run leaded in a bike that requires unleaded only. Sorry for the lack of info.

What is wrong with running leaded in a bike that requires unleaded?

[unforgivenracing]

What is wrong with running leaded in a bike that requires unleaded?

Yea, I was wondering that too.  I would think that the presents of a lead additive would help prevent damage to the valves.  Or am I going crazy?