i just built one for a friend. it's a lot faster than the regular GT5.
starting isn't a problem, it does have noticeably more compression, but it'll start.
the main problem we're having is blowing head gaskets (2 so far in 2 weeks) and warping the head. the head is really thin with a tiny combustion chamber.
also, it seems to run a lot hotter. with the carb needle in the second notch like normal california bikes, the plug's almost white. trying it on the 3rd notch now.
i'm gonna build another one for me this weekend, so i'll start a new thread on the results.
there's also this post where i detail the specs of it: http://motorbicycling.com/f4/new-201...awk-33144.html