I replaced the rear gears with 15% taller gears in my 2010 Kymco Yager GT 200i (174.5 cc), and the bike hits 86 MPH now. There's no reason the Like 200i can't do the same (or close to it). I wanted to be able to cruise at 65 MPH at 6500 RPM, but it's actually 62 MPH at 6500 RPM... likely because the Gates Boost+ belt is a bit narrower than an OEM belt. I can cruise around town (speed limits up to 40 MPH) and the engine never gets over 5000 RPM.
Here's what I did:
1) Do a hard break-in. Don't baby the engine. You've got to get those rings to seal extremely well to get good compression. If you did baby the engine when breaking it in, take it out and thrash it... it won't be as good as it would have been if you'd done a hard break-in, but it'll improve ring seal. The best way (in our case) is to put heavy weights in your variator so the engine has to pull really hard at lower than normal RPMs, then take it out on the highway (preferably one with gentle but long hills) and blast up the hills with the engine pulling hard, top the hill and take the engine up close to the rev limiter, then vary the engine speed on the way back down the hill, including slapping the throttle completely shut and letting engine braking go on for a time from top speed. Do it in the early morning hours so there's no traffic, so you can vary your speed up and down, stop and accelerate, etc. After 50 or so miles of this, you should see better ring seal.
2) Pulstar HE1HT9 spark plug. I tried iridium, copper core, etc., but had a rough idle and not as much "oomph" as I get out of the Pulstar. I'm really impressed with the Pulstar. Expensive, but worth it, in my opinion.
3) LiquiMoly Ceratec. This coats the hot sliding-friction parts of the engine with a low-friction ceramic coating... meaning the ring / cylinder interface. This makes for extremely low blow-by and better compression. Only use this after your engine is broken in... 1500 miles or so should do it (once you no longer see tiny metal flakes in the drained engine oil). Use it for 1800 miles (3 oil changes for me), 60 ml per oil change.
4) Tungsten Disulfide. This coats the entire interior of the engine with one of the most lubricious materials known to man. Only do this after you've used the Ceratec. I put in 8.5 grams of 0.6 micron WS2 in each engine oil change, and after my new rear gears are fully worn in, I'll use 1.75 grams in the gear oil.
5) Valve lash. Adjust it 0.01 mm tighter than factory specs. In my case, I adjusted it to 0.09 mm instead of 0.1 mm. Not a lot of difference, but it very slightly advances valve timing, and gives a tiny bit more valve lift.
6) 20 gram Dr. Pulley sliders. The 17.5 gram OEM rollers and 18 gram Dr. Pulley sliders I'd tried were too light and the engine would hit the rev limiter even when the throttle wasn't fully open. Even the 20 gram sliders are a bit too light. I'll go to 21 grams when these wear out, but I think 20.5 grams would be just about perfect, so I might end up buying the 21 gram sliders and Dremeling a bit.
7) Gates Boost+ kevlar belt
8) I extended the torque cam grooves in the clutch a bit, and shaved ~1/2 mm off each sheave face on the clutch and variator for a slightly wider gear ratio. I also corrected a manufacturing defect in the clutch whereby the clutch swing-arms would swing inward and stick in their anti-rattle dot channels. I widened the channels just enough that the clutch swing arms could fully seat, but can swing out easily without sticking. That makes the speed at which the clutch engages much more consistent. I also polished and greased all the pivot points in the clutch so there's no friction to make things stick.
9) Hybrid ceramic bearings. I put micro-polished and WS2-coated hybrid ceramic bearings in the rear gears, clutch and wheels... the thing rolls insanely easily now.
10) I use synthetic engine oil, gear oil and grease.
I've got an order in for a Dr. Pulley HiT clutch. I'm going to adjust it for a very low engagement speed (2800 RPM engine, 1000 RPM clutch), with little slip. That'll reduce the wasted energy converted to heat of clutch engagement, make the clutch last longer, and make low-speed riding more controllable.
