I'm just browsing and looking for some nice pictures of a red qt50 (used to have one back in the day) but I can help you with your search for more power. First pull the head and cylinder and clean all the carbon as mentioned earlier. It also helps to use a good sparkplug. I enlarged the intake air horn on the carb and radiused all the hard edges inside it...then followed that up with a full polish on the inside of the carb. You can pick up a lot of power by smoothing out the little intake pipe between the reed valve and carb...You need to use a die grider or dremel with a long carbide bit. I enlarged and contoured the ports in the cylinder, and also milled the head for some more compression. You can add a k and n filter to the carb if you get rid of the stock side covers over the air filter housing. If you want to know more just email me at matpei@yahoo.com