Thanks very much dude.. Much appreciated..
My daughter has been crazy hyper all day, Itching to ride it 
Been doing a few checks on it tonight... Compression test, inspecting and re-greasing swing arm bearings etc etc
So will be letting her have a rip on it tomorrow...
She is far from a "race pace" skill level yet...
I'd say... her PW50 was too slow for her, and holding her back... But she will now require time to gain confidence on a new bike, before she will start opening it up...
So based on that.. It would be fair to say, Many more than 20 hours to a piston 
After she has her fun on it tomorrow, I will be pulling the head off, measuring the barrel etc, and ordering up a new piston and gasket set for it..
£65 for a Vertex piston, and gaskets, Seams good to me 
I must admit though.. I dont know how i feel about the fact that it has no restrictable clutch...
My daughter more than likely wont require it.. She has pretty good sense of throttle control... But still... Would have been nice to know its there, incase...
But i cant grumble too much.. £500 for a tidy little bike... Well happy and on top of that.. Sold her 2014 PW50basically instantly, for £900... So defo quids in
