So I just bought a HSP 1/8 truck with the SH .21 engine. I went through the entire sealing the engine process and break-in. Is it normal to have to re-tune the engine every time you run it? I can have it running great one day, then the next it won't start. Then after tweaking the lsn and hsn it will run good. I just don't know if this is normal or not. There has been no significant differences in ambient temperature. Also, is there supposed to be fuel in the line between muffler and fuel tank? I noticed mine doesn't. Last question, with temps in 80's and 90's should I be running a medium glow plug? All help muchly appreciated.