Re: "Highest RPM I tend to get is about 13000."< this number doesn't tell us anything unless you include which brand prop and which size. I can have a 2000 rpm rpm difference just by changing props. Also consider trying 10% nitro fuel. That will give you more power without overheating the engine. I found it to be a good all around fuel that works well in all my engines. You might also want to consider removing the fuel tank and inspecting it. Fuel that is just sitting can turn gummy and plug lines and the fuel pick up.[8D]