There are may members here who have the kit you showed. I'm sure someone else can advise. The only thing bad I have to say about my GEBE set up is the fuel tank is too small. The tank in my photo, I only get 25 miles and it starts to sputter a little. I always carry extra fuel in a small camping white gas tank. They do make larger tanks but they are bulky or sit off to the side. many like them, but I dont like the look. (Personal preference) I do have to say I LOVE the engine though. I've heard of people with 5-10,000 miles on them.
http://www.bikeengines.com/info.htm
Hope someone will chime in about the 4 stroke I provided a link for and let me know what they think about them. I've heard nothing but good things about the GEBE units (with the exception of one person on a wild rant). Everyone seems to be really pleased with them. Can't you use one of the frame mount gas tanks? Or is that not possible (sorry if that's a dumb question). I'm so new at this I don't know. 10,000 miles is awesome!!! That's killer. Can't help but love that.