The bajajusa manual advises the user to clean the air filter with a stoddard solvent. What is a stoddard solvent? Varsol - a kerosene like compoud available from Exxon - is a common stoddard solvent. But most petroleum based solvents will work, they just vary in flashpoint (e.g. flammability and explosiveness) (gasoline is high, kerosene is less). That is why bajajusa recommended a stoddard solvent. So if the backyard mechanic used gasoline and did not let the filter dry and the scooter exploded, they couldn't sue bajajusa. There are numerous commericial "foam filter" cleaners on the market that will work.