i bought a boygofast kit couple months ago, it's working fine. i bought another one last month, its also working well. the first engine has a more gracile looking head and had some weird silvery paint on it. the second was a more rectangular head with no paint.
first was adverts as an 80 2nd was as a 70, theres no discernable diff in the power between the 2. if i get another unpainted one i guess i'll go ahead and paint it to keep the whitish corrosion at bay.
i have dealt with both and i was not happy with bgf at all and really pleased with dax. dax answered all my questions and was thier to help when i needed it. i did not the frame adapter with my boygofast kit which the ebay add said was included and he pretty much told me it was a mistake and to bad.
my first was a kings "80cc" sq. head my second was a bgf also sold as a "80cc" with rnd. head really no diff. the bgf started right up and worked good , so I purchased 2 more motors from bgf (cant beat the price!) that supposed to arrive on the 6th. I got a quick response from bgf the first time. all in all though there pretty much the same , some have rnd. heads some have sq. heads , some are painted its how you tweak the motor to make it run good. I will let you know tomorrow how the engines look!
I have bought from both vendors...
dax is slower shipping, but gives better service and answers tech questions over phone
bgf ships faster but has worse after-the-sale service
I've never had probs with either engine