I don't really like the look of your cracked case, somebody had to be abusing it pretty good to do that. Is that shaft for the gear shift lever? So I'll assume that the cracked case allowed all the oil to drain out. Can you kick it over at all? I'd be worried whoever smashed the case wouldn't bothered to stop riding it until it siezed...
Assuming that it's fixable at all, I would just fix it to stock, try it out, if you find its to slow for you and you still like a motorbike, sell it and get Ninja 250. The 250 will get nearly the same in town mileage plus you can ride on the highway with out fear of imminent death. People take them across the country all the time. I don't think insurance will be any more for the ninja than the C70.
If you like the C70 and the motor dies, I believe many of the made in china crappy kids dirt bikes and atv's at walmart type stores have a knock off of this engine and tranny, I imagine there are 1000's of them not running due to simple malfunctions and they are not "worth" fixing, check garage sales etc...
Ian
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