Gy6 big bore kit?

[swiftscoot]

I totaled my Chinese gy6 and upgraded to the P150.  I'm looking to cruise at 60-65 mph and am trying to decide if I should throw my kit in there.  It's a NCY 62mm cylinder kit, and a Taiwanese 62mm head.  I fear I'll be cracking the crankcase just to put in inferior metal, therefore disrupting the longevity/reliability. Plus I'll have to install an oil cooler.

I'm planning on a Two Bros exhaust; and I want to get rid of the air box, because those are just ugly. 

Other than that I have an NCY intake and an OKO pullslide carb, that wouldn't go in unless I kitted it. 

I'm thinking skip the kit, throw on the pipe, up jet, and maybe tune the variator and call it good.  What do y'all think?

[John in PA]

What will the final displacement change be?  Are you looking for take-off or top speed?  Review my mods and assessment before doing a lot of changes.  Seems much harder to get extra oomph out of these scooters than it is on a motorcycle.  And, you'll be pioneering new territory in all probability.
 I've wondered if a Non-CV carb would get a bit more punch out of it, but I'm a bit disappointed in return-on-mod-investment so far, and don't want to put on an untried carb and have to rework everything from scratch.

[swiftscoot]

It'd put it up around 175cc.  I'm looking for top speed.  I found out that a stock cylinder on a P150 is over $200 dollars, meaning they gotta be top notch quality.  I really don't wanna crack the perfectly sealed crankcase either.  

I was running that 30mm carb without a kit and it was so-so.  It had great acceleration and would get up to 40-50 mph at about half throttle.  The problem was without the extra velocity it had awful throttle response.  I had to ease into the throttle to get up to speed.