Pulled up this thread just to remember what all I have tried in the past. Looks like the links are dead and there is no option to edit them, I might look for them if I get time.
Just to update, the kids managed to break the crank on their Hisun. I replaced it with an ebay crank then put it on my bike just to run it for a while and make sure it didn‘t grenade. Gave them the Baja engine in the meantime. The Hisun ran so well, I decided to build it. I think I started a thread on it, I’ll look for it. But long story short, billet rod, PVL flywheel, 22 lb springs, CS 265 cam. Tried a Chikuni that looked exactly like the real VM22, but never could get it to run. Decided to try a 24mm Nibbi and it dialed right in. Runs great now! We’ve got less than 200 yards of runway on the property and you need to stop before the end, but I can get up to 35mph and 6000 rpms in around 150 yards, and I am pleased with that. Might try to get a video sometime soon.