My old montesa seemed like it had a lot of knock on 91 octane 10% ethanol fuel. I bought 5 gallons of 110ll avgas to see if that helped, it didnt. But now that i've upgraded to a 2012 Sherco ST300 I was going to burn the rest of that fuel up. I've read lots about avgas and leaded fuel. Seems there is plenty of debate about its benefits and health hazards. But I haven't seen anything about it causing massive damage to the engine just that you'll get lead deposits on valves and spark plugs. Yet A beta dealer on my local group chimed in and said "Horrid thing toy do. Avgas is no bueno for a motorcycle". He has yet to explain why he feels that way. But has anyone else heard anything that negative about avgas? Finding race fuel or anything over 91octane in my area is pretty tough, but I can cross the street and buy avgas.