Yamaha YBR 125 was not designed for speed , but for reliability and economy , which is why i bought one for , i have not fitted any of these parts to my bikes but they are are out there and i might do one day just for fun .
here is some that i know of probably lots more if you can add anything or have tuning information
for the yamaha ybr 125 then post below .
obviously there is the exhaust not sure if these improve speed any but they look and sound a lot better .
buy one here on ebay uk
Amazon UK do a Sports exhaust for the YBR 125 as well buy it here , see photos below .
You can also get big bore cylinder barrels to increase bore from 125cc to 150cc
you can buy them only on ebay uk as far as i can tell , buy them here .
any link below in the posts please .
i did find this though during my search for info claim 15% bhp increase ?
DYNO-BOOST PERFORMANCE CHIP Yamaha YBR125 YBR250 YZF-R125