Do I need race fuel?

[wysguy]

I have a 2006 YZ250 and have been riding it for a couple months.  It seems to run well, but I am coming from 3 previous 4 stroke bikes so I am not well versed in 2 stroke performance.

Two other riders that I know that have quite a bit more knowledge than me on 2 strokes say that they went through pistons within 5 hours on their YZ250's because they weren't running high enough octane fuel (race fuel).  They both said they ran premium but recommended that if I continue to ride/race my YZ that I run race fuel, or at a minimum blend it with premium gasoline.

This seems like a huge distraction for me as race fuel isn't immediately available, not to mention expensive.

Maybe some background is helpful; I ride 2 -3 days a week all MX tracks.  I race monthly in C and Vet classes, so nothing too fast, but still competitive.  I am mechanically inclined, I rebuilt the top ends' of my 4 strokes in the past and am not afraid of rebuilding my 2 stroke now.

The bike runs well, the spark plug tells me the jetting is reasonable.  I currently use Sunoco 93 octane with 32:1 S2 oil.  I haven't pulled the head to look at the piston, but plan on doing that in the near future.  I do however notice some odd sounds from my YZ but because I am not used to 2 strokes they may be normal.  I cannot tell if it is detonation or just "2 stroke rattle".

Any advice?

[ACMX]

Bikes tend to last longer and happier using an octane of around 104. I buy some 108-110 and mix that 50/50 sometimes 60/40 with premium to keep it around 102-104.

[MXLord327]

If I remember correctly, the '06 did run right on the edge of detonation with pump gas.  I think Yamaha put a different needle in the carb for '07 to cure this.  If you don't want to run race gas, check into the new needle.

[wysguy]

If I remember correctly, the '06 did run right on the edge of detonation with pump gas.  I think Yamaha put a different needle in the carb for '07 to cure this.  If you don't want to run race gas, check into the new needle.

A needle change seems much simpler, and cheaper, than finding race fuel to ride.

I appreciate the advice.

[motomike894]

Try the needle I guess but all my Rm's and my 04 and 05 Yamaha's almost always would detonate without at least running like 1 gallon 100 to 3 gallons 93, I am now running half and half, and sometimes totally race gas, but the price isnt much different.

There are 2 gas stations that sell 110 around me and its like $5.89 a gallon, hell 93 is like $4.09 a gallon right now.

[ACMX]

I would advise against using only pump gas. Most of it is 15% Ethenol, which will gum up your carburetor and your bike will not run well. Here I can get 109 octane for just over $10/gallon and 108 for just over $8/gallon.

[snook620]

Every 2 stroke Ive had LOVED race gas. You can tell a defference from the minute you go to clear it out.

[ACMX]

Every 2 stroke Ive had LOVED race gas. You can tell a defference from the minute you go to clear it out.

yep

[MyckMcClung]

I just found an old school gas station with non ethanol 93  it's cheaper than most other places in town too. Gonna get me some of that this weekend.
As for race gas I have used it in the past on my YZ250, it needed it, my KX not so much, when I first got it, it would detonate occasionally on 93 but only if it was last weeks gas. Since I lowered the compression (with two high compression base gaskets) I haven't had a problem , the gas in it now is 3 week old 93, started it up yesterday and it ran fine.

[yo_marc]

It's funny, here in Mass I can get away with 93 just fine.  I've had my bike (2000 RM250) detonate, but only by jetting it too lean.

I'm not sure what our ethanol content is.  I want to say 10%, but I'm not certain.

[VintageBlueSmoke]

My advice is not to use race fuel if you can get away without it. My reasoning is this: As a Vet C rider, the performance gain from the fuel will not be worth the added expense. You would be better off saving the pennies (nickels and quarters!) and putting the money to a riding clinic or school or a new set of tires.

The caveat of course is detonation and piston life. Be sure jetting is correct and you get good fuel. SAMS CLUB or the 7-11 down the street will not have the best quality pump gas. You might pay a little more, but in the long run, it is worth it. Also, at the more expensive gas stations, you stand a better chance of finding non-alcoholic fuel.

Back when I was traveling a lot to the races, I noticed higher gas mileage in my tow vehicle if I spent the little bit extra on good gas. It always worked out in the long run.

[Coop]

It's funny, here in Mass I can get away with 93 just fine.  I've had my bike (2000 RM250) detonate, but only by jetting it too lean.

Same here. Heck I have run 89 in my KDX before with no detonation, pinging etc. I wanted to ride and it's all I had here (I use the cheap stuff in the Craftsman tractor  ) so I mixed it up and it ran fine. I do not race, but I ride hard.

[wysguy]

My advice is not to use race fuel if you can get away without it. My reasoning is this: As a Vet C rider, the performance gain from the fuel will not be worth the added expense. You would be better off saving the pennies (nickels and quarters!) and putting the money to a riding clinic or school or a new set of tires.

The caveat of course is detonation and piston life. Be sure jetting is correct and you get good fuel. SAMS CLUB or the 7-11 down the street will not have the best quality pump gas. You might pay a little more, but in the long run, it is worth it. Also, at the more expensive gas stations, you stand a better chance of finding non-alcoholic fuel.

Back when I was traveling a lot to the races, I noticed higher gas mileage in my tow vehicle if I spent the little bit extra on good gas. It always worked out in the long run.

Not to sound ignorant, but how do you tell which gas stations sell good fuel?  I chose Sunoco because of word of mouth.

And yes, I have no need for the performance gain, the YZ250 is plenty of bike for me and the class(es) I race.  I just wanted to treat it properly so it won't fail prematurely.

Thanks

[wysguy]

Last night I decided to pull the head off just to have a look at the cylinder.  I could see no signs of damage from detonation, and I would suspect the jetting to be a bit rich although the plug likes just about right.

I am going to do a little scouting around to see if I can find a local station with race fuel as it is not a matter of the expense but more of the hassle to always have some on hand.  I guess the 4 strokes have babied me and I am used to grabbing fuel on my way to the track.

[VintageBlueSmoke]

Again, just from my experience; Mobile, Sunoco, BP, Shell, (surprisingly) Hess - the name brands. My guess is that they have more at stake than the budget operators so make their franchises live up to a higher standard.