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Uhhhh stupid question...which gas?

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Hey guys, so I've been running premium through my 2005yz. Around here premium is 93, well I just randomly noticed the PDF manual I stumbled upon claims 95 or higher. So does that leave me to need to run race gas...?

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Not really.  I've tried 87 octane regular, and it ran.  I've also tried 110 race gas.  But I regularly run the highest grade pump gas I can find.   It's more convenient and a lot cheaper than 110.

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Hey guys, so I've been running premium through my 2005yz. Around here premium is 93, well I just randomly noticed the PDF manual I stumbled upon claims 95 or higher. So does that leave me to need to run race gas...?

run 93

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ah someone that didnt read the very FIRST part of the forumfaq.

.

Sunruh FYI the FAQ isn't all that these days. Also the search function isn't much help.

Besides this forum needs something for us to discuss or FNG to pick on! :)

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so running a 110 leaded race fuel ok in these engines?  I typically like to mix some with 91 or 93.

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Not really.  I've tried 87 octane regular, and it ran.  I've also tried 110 race gas.  But I regularly run the highest grade pump gas I can find.   It's more convenient and a lot cheaper than 110.

Uhmm... I would NOT run 87 octane just to try it. Get on the power real good and you'll likely hear a loud screechy sound, followed by a violent sound, and then a really quiet sound.

Edited by BazookaJoe
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so running a 110 leaded race fuel ok in these engines?  I typically like to mix some with 91 or 93.

 

1st off, why would you think it is NOT ok to use?

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1st off, why would you think it is NOT ok to use?

 

I have heard that if piston/ring interface is not designed to be used with leaded fuel it will create issues with the pressure on the cylinder walls.  I have also heard that modern valve guides/valves are not clearanced to withstand the lead in the fuel.  I could be wrong and it has happened many times in the past but this has been my understanding of a possible downside of running leaded fuel in newer motors.

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Don't forget the real reason for higher octane fuels: to prevent pre-detination.  Higher octane fuels do not in and of themselves add power, but they do allow you to run a higher compression ratio (which these 250F bikes are high compression), which does produce higher power.  Whatever additive is used, it slows down the flame front and flame propagation across the combustion chamber as a way of preventing high pressure zones in the chamber which will burn on their own without a spark.  Usually this occurs at different time than would normally occur, and that causes problems, hot spots, and basically the engine will have some kind of failure as a result. 

 

Don't forget that because of the slower burning, it can make an engine harder to start, especially when its cold outside.

 

Octane can be raised by lead (not readily availabe any more) or by other additives in the fuel.  Carbon buildup on the piston and head will raise the compression slightly, and when it flecks off, get lodged in the sparkplug and short it out (usually more often in a 2T).

 

The recommended rebuild time on the Yamahas is 25 hrs, which from what I've seen, is not enough time for a large buildup of carbon, unless the jetting is really fat.... just my experience.

 

If anyone is interested, look up aircraft fuel, 100LL, and others.  It makes for a really good science project/report, as do sparkplugs.

Edited by ronbuell

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I have heard that if piston/ring interface is not designed to be used with leaded fuel it will create issues with the pressure on the cylinder walls.  I have also heard that modern valve guides/valves are not clearanced to withstand the lead in the fuel.  I could be wrong and it has happened many times in the past but this has been my understanding of a possible downside of running leaded fuel in newer motors.

 

hearing is a lot different than seeing.

 

you will encounter many more issues by running pump swill than any issue you can dream up by running a quality leaded race fuel.

and i've been running leaded race fuel in a yz250f since december of '00 (vp c12 and also howell 002).  yes thats 14 years.

however i like vp ms103 better.

while 100LL is better than pump trash, its evap points show that its not idea for throttle changes like on a bike vs the set and go on a plane.

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hearing is a lot different than seeing.

 

you will encounter many more issues by running pump swill than any issue you can dream up by running a quality leaded race fuel.

and i've been running leaded race fuel in a yz250f since december of '00 (vp c12 and also howell 002).  yes thats 14 years.

however i like vp ms103 better.

while 100LL is better than pump trash, its evap points show that its not idea for throttle changes like on a bike vs the set and go on a plane.

 

I will find out what our local gas station has available to run at the pump.

 

Here are the different options...All I know at the moment is the local store has 110 octane, but Im not sure which one.

 

Race Fuel Products
  • Unleaded Sunoco GTX 260 (98 octane)
  • Unleaded Sunoco GT 260 (100 octane)
  • Unleaded Sunoco GT Plus (104 octane)
  • Leaded Sunoco Standard (110 octane)
  • Leaded Sunoco Supreme (112 octane)
  • Leaded Sunoco HCR (114 octane)
  • Leaded Sunoco Maximal (116 octane)
  • Leaded Turbo Blue (110 octane)
  • Unleaded Turbo Blue (100 octane)

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as i have posted before, Hot Rod mag did a test and proved that you actually want a LOWER octane level that still prevents pre-ignition and detonation.

 

while the 250f's have a static cr that seems quite high, it actually is not very high while at rpm.

 

stay far away from gtx 260...it will cook off in your garage this summer.

even gt 260 would not be wise at my house.  it might be ok in michigan, but not here in texas.  gt260 plus is also not an option for me.

 

turbo blue unleaded plus looks darn good

turbo blue unleaded looks good too

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