I have problems with my gp aswell. it has stupid intermitent problems like wont start on a cold day and other little crap. the engine has no guts just like yours and was imposible to start untill I got a electrict starter and cracked it for 30 min. I was so pissed!!! peaople say your a mad model flyer just cause of one bad comment about the thunder tiger and they told me (going on for hours on end about how "good" it was) and calling me a blatent lyer for saying some thing bad about them.
my advise is to not put any more money or time into thunder tiger engines and stick with a brand that is good. im even considering goind electric and ditching these glow engines all to gether.