Gearing calculator spreadsheet

[Yager200i]

I'm planning on getting new rear gears cut for my 2010 Kymco Yager GT 200i such that I can cruise at 65 MPH at 6500 RPM, the engine's torque peak. That'll give maximum fuel efficiency at highway speed. I'm also planning on getting them spiral-cut, to get rid of the gear whine of the OEM straight-cut gears.

There were three scenarios I was considering:
1) New rear gear set with OEM variator
2) Wide range variator with OEM rear gear set
3) Wide range variator *and* new rear gear set

I created a spreadsheet to do the calculations. It's in OpenOffice.org Calc format, instead of Microsoft Excel format. I like OpenOffice much better than MS, and it's free.

This will allow you to see just how fast your scoot is capable of going. For instance, with the OEM variator and the OEM rear gears, if I push the engine to its rev limiter, I should be getting about 79 MPH... but I've only ever gone that fast once. I recently found that a very tiny outer section of my variator isn't being utilized, the belt's not riding all the way up... so I've begun shaving the variator little by little to rectify that and get the full speed capability out of the bike.

The fact that I only ever hit that speed once despite regularly hitting the rev limiter if I'm not careful also tells me I need heavier Dr. Pulley sliders. I'm running 18 gram sliders now. I'll buy a small bench lathe and turn my own custom weights to insert into the sliders (I'll also have to find a small Dake press for pressing the cores in and out), so I can test out a variety of weights. I'm betting about 20.5 grams will be just about right.

See the attached "Gearing.ods" spreadsheet, in .zip zipfile format (because KymcoForum.com doesn't allow .ods files to be uploaded, but they do allow zipfiles).

[zombie]

Ahhhhh, Welcome to "The Dark Side" Yager!!!

You can go heavier on your rollers/sliders to achieve what you want. It will have the same trade off as what you propose. It will reduce 0 - 60 times/ hill climb ability, but it will cost far less.

In either case you can slightly compensate using a stiffer control spring in the rear pulleys.

You can also go larger on the rear tire to lower the cruise rpm.

Keep in mind you may need to go to a longer belt when you shave the variator. I ran into a limit where the belt was stretching to the point of pre-mature failure.

All that being said... I like your style sir!

[Yager200i]

I've only got a tiny little bit of the outside of the front sheave that's not being used. I figure if I shave the variator face down little by little, I can get it dialed in just right over time. When I stop seeing engine RPM dropping down a bit after a shaving, I'll know I've reached the 'stretch limit' of the belt... it won't go any more without unduly stretching the belt.

That said, dropping the engine RPM down to 6500 RPM at 65 MPH will take more than just variator / slider / spring tweaking. Right now it'll cruise at 65 MPH at about 7250 RPM. So a 750 RPM drop. I've picked up about 3 MPH at any given engine RPM (or dropped the engine RPM by about 250 RPM for any given road speed, whichever way you look at it) by shaving the variator a bit.

I can't go with a larger tire, it'd rub on the back of the engine.

I'd like to do it all with a wider-range variator (2.8:1 to 0.7:1 range), but I can't find any. Know of any that'd fit the Yager GT 200i?

The variator is 126 mm and has 21 splines.
The clutch bell ID is 130 mm and has 19 splines.

I could probably get away with going slightly larger on the OD of those, though. But not much unless I machine down the lip of the gear casing and cut / modify the belt cover to accomodate the larger sheaves.

[zombie]

I did about 1/2hr of searching, and found nothing. You share the same crank w/ some other Kymcos, Dink/Grand dink, and some Sym bikes, Blur, but no one seems to have an over range Var for that crank.

If you have access to a lathe... How about welding enough material on the outer rim, and turning that down to gain a few mm's.
I wish I thought of that when I was searching an overrange for my bike. Seems a simple solution.

You would need to go up 5 grams to meet 750 RPM drop. Accel would go to sh**. You might find the same thing w/ higher gears too. I did w/ the zx. I had to tow up to 30mph to get going. You have 150cc more but I THINK the result will be similar. Not sure.