E85 like in Minnesota and a few other places? Rejet of carb depends a lot on actual make, model of motorcycle and carb. For instance, a 10 to 20 year old Honda carb might have a direct interchange with a Brazillion carb of similar model- the 125 single has been done in Minnesota a couple times with simple replacement with the Brazilion carb. Others for a few demonstrations and racing- rough rule of thumb is start with a 10% bigger main jet on the throttle plate models with choke. for slide valves with 5 grooves- lower clip to bottom and test run, might need drill out 5% and idle may need 10%. Be aware that fuel petcocks and plastic floats can be eaten by E85. Most cycles since late 1990s have been E10 compliant. E85 on latest is 5% drill main and idle jet larger to start. The very early carbs with replaceable jets instead of press in/cast in jets. or the Mikuni aftermarket utilities can be relatively simple parts exchange jetting.

I guess you are asking if a carburetor must be re-jetted to run 10% ethanol gasoline. Nupe. There are plenty of old motorcycles out there chugging along just fine. The problem with ethanol and carburetors is that it increases the solubility of water in the fuel and can increase corrosion--but that is not really much of an issue. The worst thing is that the ethanol attacks the float material. There are aftermarket and sometimes factory upgraded floats available which are ethanol resistant. Find some online users groups for your bike with discussions on carb rebuilding.

Exoplanet is spot on. Unless you have some sort of lean/rich condition indicated by a plug chop or a flat spot in the throttle there is no need to go mucking about. Tuning a carbie is a time consuming process and you need to know exactly what you are adjusting and what effect it will have. idle, main and needle jets all perform different functions at various throttle openings. You don't even mention what type of carb this is. CV, Concentric what? I suggest you leave it alone until you up your knowledge of what you have. You need to be smarter than what you are working on.

Hi you would need to go see a motorcycle dealer for the parts.