ok, first thing before i forget is take the roto start plate off and the back plate to the engine and lock tite them or they will work loose and destroy your one way bearing.
Now, the stock clutch shoes and springs arent that great. I would replace those and also check the clutch bell bearings. I had a similar problem and replaced the shoes and stiffer springs and that took care of it.
It also could be improper tuning or a glow plug going. In the coler weather you need to run a hotter plug. My first thing to chk out would be the clutch shoes and springs. This is a nice fast car though you will like it!! A ton of hop ups avail for it too. Hope this helps
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