Small block virgin

I'm going to build a small block engine for my kid brother and like me he's not getting any smaller.
He doesn't want to change the original casing out to put a 200 in but he wants something faster than
the 125 motor that was in it when bought.I've got a 175 top end,22mm jetex and 42mm AF Clubman
lying around.The thing is the only gearbox that he has is the original Li125 with 15 tooth front sprocket
and I've got a 46 tooth solid crown wheel he can have.Would this set up work well enough in a series 3
mostly ridden one up and give him a descent cruising speed.
He doesn't need a balls out race machine just a useable scooter and he hasn't got the money to put a Casa,
GT186 or RT kit on it,also the original Li crank is in good condition but he would like to put an electronic
kit on for reliability.Would the crank be ok or would you swap it for a GP crank and if so what crank would
be sufficient for this set up.
Would appreciate any feedback
Regards Mark
He doesn't want to change the original casing out to put a 200 in but he wants something faster than
the 125 motor that was in it when bought.I've got a 175 top end,22mm jetex and 42mm AF Clubman
lying around.The thing is the only gearbox that he has is the original Li125 with 15 tooth front sprocket
and I've got a 46 tooth solid crown wheel he can have.Would this set up work well enough in a series 3
mostly ridden one up and give him a descent cruising speed.
He doesn't need a balls out race machine just a useable scooter and he hasn't got the money to put a Casa,
GT186 or RT kit on it,also the original Li crank is in good condition but he would like to put an electronic
kit on for reliability.Would the crank be ok or would you swap it for a GP crank and if so what crank would
be sufficient for this set up.
Would appreciate any feedback
Regards Mark