125SX Gearing For Road Racing

[Thack]

I am going to road race my 125SX. Right now it has the stock wheel sizes. What gearing would be good to start off with? The tracks in Texas have top speed straights.

[hellish100]

I'll let you know in a few weeks. Is there a certain class you'll be racing in? otherwise you might find yourself having a hard time keeping up with the bigger guys.

[rhythmofbeing]

What tracks are you going to be at?

At any track faster than Oak Hill I run 16/42 on my 650R. I doubt you want that on your 125, but maybe it'll give you an idea. You might also research the gear ratios and final drive on 125 GP bikes and see if there's any similarities. Those little guys are FAST.

[Thack]

Yeah I had a '92 RS-125. It was fast and super buzzy. I could barely read the tach. Your 650R has way more motor, hence the 16 front sprocket. I'll start off with 14/42 or 40. Then if it's a faster track I'll get a 15 front, if it's slower I'll run the 13 stock front. Texas World I'm worried about but I don't expect to be in the chase. Just want to get my feet wet and do some Supermoto when I can find it. I love Oakhill and Cresson.

[Thack]

oh yeah, like in motocross when I race my 250cc friends, I make up time going into the corners. Those stock Brembo front brakes are awesome. The best I've seen on a dirt bike, period.