Great advice, from Dirt Bike Mag, July 05, page 76.

FUEL! by Gary Hazel

"We tell all of our riders who have new CRF, YZF, RMZ or KXF bikes that they should run a MIXTURE OF 50% RACE FUEL TO 50% PUMP GAS, even if the motor is stock. This insures that you always have good quality fuel in the tank. A few years ago fuel quality was great all across the U.S., but it has gone downhill. In some cities they use additives to help keep emissions down. These additives hurt the performance of the fuel and in the end hurts performance of our bikes."

"We have heard all the stories about valve issues in the new bikes. We have found that riders who live in the cities that use these environmentally friendly fuels seem to have more troule with valves that others do. In most cases we've found that the octane of the fuel in these cities is 91. When I worked at Kawasaki back in 1994 and the KLX250 was intorduced, we had motors coming back in to the shop that could use a set of intake valves after just a few hours. We found that DETONATION WAS THE MAIN CAUSE of this and when better fuel was used, this trouble all but went away. I think I can reinforce this with guys who are taking their new CRF250X's to Mexico. I have talked with guys who've said that they rode 400 to 500 miles and the valves have tightened up. Fuel in Mexico is very low quality, and these guys have told me that the bike was brand new befor the trip. Nearly every time they return after running that gas, you can plan on a valve job, because the top end takes a beating."


I unfortunately live in one of those areas where premium pump gas is 91 octane. My personal solution is to run pump gas, and bump the octane up a couple of octane using Klotz octane booster (http://www.klotzlube.com/storeProdDetails.asp?pi=50). I prefer the octane booster because it also contains an ester synthetic lubricant for the upper cylinder (which I prefer to the lead in race gas), and it has preservatives specifically intended for oxygenated fuels.

 

I don't know what valve issues they were having but I have never seen issues with valves dealing with detonation. Pistons; ya; head erosion; ya; head gaskets; ya; rod bearings hammered; ya; even cylinders split, but never valve troubles. Maybe some valve head erosion but by the time you see any big time head erosion your piston is burnt in half or the electrode is gone and your done anyway. If he is talking about valve face or seat I say BS. The valve is seated when the detonation is occurring.
I have smoked pistons from detonation so bad that it melted into the second ring land and the valves and seats were perfect.
I remember in the 70's Honda had very soft valves in some of their engines. It had nothing to do with poor gas. With modern stellite seats I don't hear any more about seat erosion. In the old days of cast iron seats, ya, but not any more. When they took the lead out of fuel they had a ton of problems, but stellite and good valves fixed all of that.
If I was in Mexico I would take some ocatane booster with me. Some products I have used will treat 120 gal. of fuel with something like 6 oz of octane booster. I don't know whats in that stuff but it works and works very well.
I don't know what this is all about either. 91 octane is 91 octane. 87 is 87. If you think you are getting ripped off you can call the bureau of weights and standards and they will pull a sample at the station where you bought the gas. I have done this several times and they all have came up over on the octane.
I agree, if you don't know how to read plugs for detonation you better have enough octane. I think anybodys best bet is to learn to read plugs for signs of detonation.

 

Hey, if you don't understand, e-mail the guy care of Dirt Bike, and ask him what he means!

If you live in California and your gas is 91 octane, then it is oxygenated (formulations can change with the season). The oxygenates degreade rapidly in storage (even for a short time), and will leave you running LEAN as well as risking detonation. As far as detonation, for myself I don't consider that as important an issue as the upper cylinder librication that I get running Klotz. And, bumping the octane up a couple of points can't hurt (although more than that would be silly). I do this for the same reason that I use the finest oil I can find........just some added insurance, for an insignificant amount of expense.

 

I know what the dude is saying. He is blaming valve degradation on low octane fuel. I just claim bovine feces on his statement, thats all.
When ox fuel is fresh it contains the most O2 in it's life time. This is when you need to be jetted correctly. Both MTBE and meth evap fairly quick. When ox fuel sits it will degrade and the O2 will boil off. When this happens the engine will go rich not lean.
I agree with you on the bump issue. If your running close to detonation you better make sure your over the top with octane.
Most of these quads are fairly low compression from the factory. My V is only a 10 to 1 motor. So it is not even close to detonation even with 87 in it. Now when I put a advance key in it I will have to see. Might have to go up one or two grades?

 

Seems to me recommended "best" fuels, oils and even quads tend to be the one's people use or own.

I've had good luck with the octane boosts, now I'm giving avgas a try. Though I'd argue either would be a waste of money in most stock bikes and quads. I know for a fact higher octane kills the power in my EX.