Hello Fella , not a 200 but a BTS GY 125. Here is what I've done over the last year, I have concentrated solely on performance, my aim was for a top end of 80 and a cruisable speed of 70.

Base line. From stock the bike hit 60 (revving it’s guts out) up and down hills and with a pillion passenger. The bike was dyno’d at exactly 8 HP. 4 less than stated by the company which sold it to me.
Cold air mix= ¾ turns out. 92.5 main jet. Needle T3.
Dyno 8 BHP Road speed 60 mph

Mod 1) changed front and rear sprocket from 15 and 56 to 17 and 51. This lost me a tiny bit of acceleration, gave me the feel of a bigger bike, a total change, pulling longer through the gears and taking my bike up to 68 MPH with a following wind but struggling to hit 58 on the way back. At 6’2 and just under 14 stone aero dynamics and physics were always gona be a problem.
Road speed 68 MPH

Mod 2) hoping to get a bit more power back I removed the stock filter box and fitted a cone filter and new 1.15mm jet. This totally messed up the fuelling and put my bike off the road for a fortnight. After some adjustment to the cold air feed and moving the needle up a notch the bike had extra torque and pulled through the gears alot faster, but was topping out at 64 with a slight stalling at higher revs, also pre-ignition when engine run hard for too long. Liking the new low down power and the snarl and popping coming from the exhaust coupled with a dyno reading of 8.6 HP which is very good considering the gear change .
Cold air mix= 2 ¼ turns out. 1.15 main jet. Needle T4.
Dyno 8.9 BHP Road speed 64 MPH

Mod 3) Gutted the standard exhaust, what a difference, lost a tad more off top end, put that down to fuelling needing more adjustment, but now the bike wheelies, I wont lie, absolutely crapped myself and nearly fell off, was expecting 6 inches of lift and nearly got put on my back. BUT! it is a bit loud lol, get funny looks from old people and scares kids.
Cold air mix= 2 1/2 turns out. 1.15 main jet. Needle T2
Road speed 60 MPH

Mod 4) I fitted the AMR CDI and spent some time trying new Jets, I tried 140, 135, 115 and back to the original 92.5. Although I have lost some lower end grunt I've gone back to the 92.5, in testing it gave me the best top end and most evenly distributed power. It just seamed that I couldn't get enough air into the carb to match such big jets. The AMR CDI is fantastic! The engine doesn’t like the advanced timing, and only seams happy going flat out forward. Not so good for a commute, but perfect for shocking a few bigger bikes. This CDI really pulled all my mods together, the engine is very responsive and revs / sounds like a two stroke.
Cold air mix= 2 turns out. 92.5 main jet. Needle T2
Road speed 72 MPH

Mod 5) Fitted the 30mm Minuki carb ... cost £35
Over all it's a thumbs up. Top speed 74 MPH (was very windy though... bit blink.gif ) cruised at 60 but got there one hell of a lot faster. Pulled me nicely up the on ramp to the duals where normally wouldn't gain speed. It does seem to attack hills more now, definitely more torque.
The Minuki carb from the outside doesn't look all that different, but internally compared to the stock 26mm carb the design and build quality are far superior. Also bored out my inlet manifold from 26-30mm.
It came with a size 100 jet and I'm hoping that a 110 or 120 might sort out the top end. Not sure it'll get me to 80 but shouldn't be all that far off. Might need a sprocket change too, cause I don't think my ass can handle anymore 70 mph vibration.

Going to dyno the bike after I source a Honda coil and re-jet the carb, really wish I could’ve afforded to dyno every mod, but at £60 a pop it wasn’t possible. Over all I can’t say anyone of the mods were solely responsible for the gains, it was more a series of adjustments made together. Although the top end gains haven’t been massive the way that the power has moved up and down through the rev range has been impressive, and I expect the next dyno to show that. The bike is a totally different machine to the 8HP slug that landed on my doorstep and I’ve had a lot of fun (and tears) along the way.

Next mods: going for a full engine overhaul. Skim the head, port and polish, lighter push-rods and possibly a one off cam.
Will put up the new Dyno report soon (fingers crossed for 12 BHP) and if anyone wants any diagrams of the exhaust or CDI mod let me know.

Hope that helps… Shy: