KX100 gearing comparable to the KX85?

[MarkSims]

I posted a question a while back asking why the stock gearing would be so tight on a KX100 (13/51) compared to the KX85 (14/50) - since I expected the KX100 to pull a smaller rear sprocket (given the same size front sprocket) than the KX85 due to its extra torque.

I was told that the gearing on the KX100 was specified to compensate for the larger rear wheel circumference (16 inch wheel vs 14 inch wheel) which makes sense.

After getting the KX100, I found the 13/51 gearing to be very tight. For you math wizards, what gearing on the KX100 would make it equal to 14/50 gearing on the KX85? That should give me a good starting point.

Thanks! Mark

 

[MX-727]

Well, if we use gear inches like they do on bicycles to equate the numbers you come up with:

These numbers are not gear ratios!

KX100: 16 inch wheel * 13 / 51 = 4.08

KX85: 14 inch wheel * 14 / 50 = 3.92

So, you'd need to put a bigger rear on the

KX100: 16*13/53 = 4.08

This assumes that the tires sidewalls are the exact same height and this is assuming that the primary gear ratios are the same. Somehow, I doubt that they are.

 

[Vic]

14/57 would be real close.

13/53 would probably work a little better.

 

[MarkSims]

Okay, thanks. It seems like the KX100 winds out fast so I was guessing I actually needed a smaller rear (or a 14T front). Maybe it's just because the KX85 is running oxygenated U2 and is jetted well whereas I still have the first tank of pump gas in the KX100 and the jetting seems to be very rich.

Thanks again.