I have seen some similar. I think they are all cool but I realized something yesterday when I was finishing up my 4 cycle install. I really am not ever going to ride a bike enough to justify spending 2k or it.
In the trike I have now I have 150 bucks in the trike. I finally bought a recondition 4stroke weed
whacker and gutted it for the engine. I got it on last night probably another twenty five in parts for it. probably three hundred bucks and that's more than I ever spent on a diy bike before.
I'm not sure the 4 stroke was all that big an improvement. I believe i would rather mix gas than try to get oil in this beast. At least it only needs to be done once ever 300 miles or so. I expect I will have to add some during break in but not change it.
I am curious to see the power profile since it is a 30cc just like the 2 cycle I took off of the trike. It is raining of course today, so I won't be able to ride till tomorrow probably. I always say building them is more fun than riding them anyway.
One interesting thing.. even though the motor is a half shaft, I managed to save the pull start for now. No idea how that will work out long term, but for now it is much easier to check the engine than having to rope or drag start the old one.