My shop mechanic said race fuel by no means increases power at all.
Yes and no. Straight high octane race gas will not add horsepower to a low compression
engine designed to run on pump gas. However, oxygenated fuel like MRX01 and U4.4 will
definately add hp, even to a stock bike. Go to VP's website and check out the various
oxygenated fuels. Those hp claims are real and verifiable. I use to run VP Ultimate 4.1
in my CRFs. It was good for 3 hp over pump gas on the dyno.
The only advantage to running race gas in a stock bike is repeatability, i.e. each gallon is
the same - a claim you can't make with pump gas. Now you have to ask yourself, "Do I
have money to burn for that?"
The owners manual on a YZ calls for "a research octane number of 95 or higher".
Not a problem. The octane number you see at your local gas station is an average of the
Research octane number (RON) and the motor octane number (MON). For example:
RON=98 + MON=88 = 186/2 = 93 Since RON runs about 8-10 points above MON, you will
be well within the Yamaha limits using premium (93 octane) pump gas.
Again, once you up the compression ratio, straight race or a pump/race mix is advisable.