the air filter, due to no reed valve in the engine, will leak some, it is routine to have to clean it periodically. be sure to shut off your petcock valve when you stop anywhere, even for a few minutes. Your throttle cable sounds like it needs a good lube, and/or strengthen your spring in your throttle body. ie. stretch it a bit( not too much though). You can lube your throttle cable with some 3-in-1 or some similar oil, I use honing oil, for sharpening stones. Someone will suggest a better alternative, like a brand name cable lube. I just happen to be the first one along. so wait for an expert to confirm/dispute! heh heh.
gl man.