I agree with Joe..
Itll foul the plug and it will also ruin the engine with excessive deposits.
I start at 18:1 for the first 2 tanks at less than 20km/hr (letting engine cool a bit after 1/2 hour of riding), then use 20:1 for the next 4 tanks keeping the speed less than 25km/hr and taking breaks after 1 hour of riding.
After that I can safely use 25:1 but dont go faster than 25km/hr until I have burned about 10 tanks in total.
oh also, make sure that you use a lower ratio like 20:1 on warm days when summer comes around .. we know how hot it gets down here in Oz!