I'm 16 as well and PLEASE listen to this advice I bought a Yamaha rz50 didn't start with problems but had one and its taken months to fix then I bought a Chinese 50cc (2015 wk wasp 50cc 2 stroke) for £650 in the meanwhile and out of the 3 50ccs it was the best, smooth and topped out at 45mph, very good for a 50cc bike. it always started and acceleration was good. I crashed it in the wet.... plastics were hard to find so I bought an Italian 'sport' 50cc, a gilera dna 50. and even though it works, is rideable and has a higher top speed, it is much harder to use and frequent issues as well as it being generally hard to use for town riding with transmission troubles and small powerband, I miss the old Chinese 50cc that was way more comfortable, cheaper to run and use and easier to ride. still waitin on the rz50 to be fixed. listen to the old guys, I didn't. buy a 2 stroke newish bike that's already been derestricted (like I did) and its likely to serve you well as it served me well. DONT try and soup up a 50cc to 125 capabilities, sell the 50cc when you turn 17 and buy a cheap 125, I haven't got to that stage yet so I cant offer advice but id assume its a similar story to my experience with the 50ccs, which is, souped up 2 strokes aren't reliable and aren't easy to ride, buy a cg or whatever for cheap and have fun with it also, don't worry about the laws, just stick to 50 at 16 and 125 at 17, and know you will spend a lot of money making an unreliable bike. because iv been at the point where I don't have wheels and had to take the bus, or it wasn't working properly so it was an emabrrasing stop at the side of the road, and in all those instances iv wished that I hadn't hit the brakes so hard in the wet after a frustrating after school detention and took more care of my 'crappy Chinese scooter'.