I own a 1993 Royal Enfield Bullet 350 Classic. Recently my city switched to 10% ethanol added petrol from the earlier used pure petrol. I very rarely use the bike; approximately one time in every two months. I have searched on the internet and also read few stackexchange posts related to this but all of them were about new alloy engines. Will this new fuel cause any harm to the engine?
Yes, it might.
There are two types of harm the fuel could cause:
- Ethanol attacking fuel hoses not designed for ethanol
- Gasoline being typically optimized for using quickly, not for 2-month storage (although storing it for 2 months is not as bad as, say for 1 year)
I would advise you to find out if "small-engine gasoline" is available where you live. It has been optimized to burn cleaner, and it as far as I know doesn't have any ethanol. Furthermore, its shelf life is much, much longer than that of regular gasoline.
Where I live, small-engine gasoline is available widely, obviously at a higher cost than regular gasoline.