125-200cc Sprocket size

Hi Guys, I've got a Suzuki Rm125 standing next to my Terra 650.

What I want to know it has a 13 tooth in front and 51 tooth rear, but the bike feels a little powerless at the bottom end, I use it to play around and tricky sections. I see the standard size was a 12 - 48 should I go back to original ??

Thanks..

The sprockets on it now produce a 3.92 gear ratio, the 12-48 produces a 4.0 gear ratio, which is lower and would give it better mechanical advantage and a lower top speed. You get the same ratio with 13-52 also, and avoid the tighter chain radius at the countershaft sprocket. It should be noted that all 125's feel pretty powerless on the bottom end!!