I have an HPI Savage .21 and a HPI Nitro Rs4-2. I found them on the side of the street ready to be thrown out. I picked them up and gave them a clean and managed to start them 1-2 times. It has been a while since then and now I want to sell them, However I can't get them started. I brought the Savage .21 to my local hobby shop and they replaced the engine, I still can get it to start. I tried unflooding the engine and still nothing. It wont come to life, same as the Nitro Rs4-2. If you know what the problem is please let me know. Thanks!