I've never hqd a bad experience with bgf, bought my first engine from him in 2009 and its stillgoing strong, I have done some upgrades to it but it was not because anything was wrong with but only because I wanted to experiment with some other parts and pieces, on another bike I'm also still running an engine from bgf and it has been going strong since 2010, its also a 66cc, bgf will work with someone and make a solid effort to make any legit issues right if he is addressed nicely and honestly, but if someone is being a jerk and starts acting out of line with him he will not cooperate, can't say I blame him either, many of the bad reports are do to people acting like an idiot with him and he just brushes them off, I've had a couple parts that were broke when I got them for shipping damage in the past and all they ask is for me to please take a picture and email it to them so they could see the problem, I did as they ask and they immediately at there cost shipped me a new part and thanked me for my honesty, im sure many people have tried to rip them off so you cant blame them for wanting proof.
I have heard that the engines he is selling now are a "hybrid" PK80 because instead of having a 40mm stroke they have a 38mm stroke, Fred the maker of the Fred heads and other parts has said they are good engines and he has bought and built some himself, all china girls are a crap shoot to some extent but it is a fact that some factories in China are known for producing a better engine than others on average and it seems that the engines bgf has are good ones.
Im partial myself to the engines and lowers tha dax and Neil ( motorbicycleracing ) sells, they are the best balanced engines I've personally had but the bgf engines I have are not the same engine he is selling now, mine are the old style and although they have been good strong engines they are not as well balanced as some of the engines that are coming out of China now days.
Best wishes and just build that lower up right, make sure the carb is tuned right and by all keans install a quality upper bearing and not the stock china bearing, notch the piston to clear intake port if you have the ability and tighten everything correctly and you should have a good engine.
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