Years ago, manufacturing tolerances weren’t as tight as they are now, and air leaks that cause finicky engine performance were common then. This isn’t the case as often now. You can protect against and prevent air leaks by sealing the carburetor (Lucky7 Air Seal works perfectly), but don’t automatically assume that your tuning problems are the result of an air leak. It’s easy to spot air leaks; just look for wet spots around the carburetor neck and fuel inlet. If you fine one, clean and seal the area. Problem solved!
Fuel? Check. Air…can your engine breathe? Don’t make your engine breathe through anything you wouldn’t want to breathe through! keep freshly oiled, clean filters installed. Some RC’ers expect their nitro engines to perform with air filters so dirty they look like dipped in chocolate and rolled in dirt. If the engine can’t breathe, it won’t run.