i own 2 gt5 kits. the first one ran great, and the second one has not been used yet. but iv had it mostly all apart, and it all looks good.
plus i added things like lock tight and new hardware to hold her together...
some simple precautions and replacements to any kit will save you a pain in the neck down the road. i have also owned a zoombikes kit. and its just as good as the shyhawk motor.(its on a friends bike now) it just came with a few different things, carb/extras. befor i rebuilt, and gave my ZB motor away. i used a few parts in my shyhawk when it broke. its all the same stuff, with a different sticker on the clutch cover. if any sticker.lol
i think most people go with kits that A. come with the carb and other kit junk they want. or B. that have a good warranty. because they are all mostly the same motors, with slight differences in what comes with the kits. get one from a site that will replace your motor if you get a junk one..
it dose happen, people get brand new motors that wont run. or that come brock and banged up.. make sure you dont get stuck with a $200 pile off cheep china parts..lol