Sprockets for the 251

Hello,
I want to try different size of sprockets in my bike. I think (I am not sure as Ihave checked) i have a 22 tooth now in the front and the machine won't take revs over 4500 with fifth gear and also chokes on climbs and facewind. No power. Fastest speed this year is about 115 km/h, down hill, backwind and the sun behind me.
So maybe a smaller front sprocket will help a bit. Also the aftermarket silencer is s**t I think.
The problem for me is to find a store which sells the sprockets. And to know if the ones for 250 fit the 251?
Thanks,
Teemu
I want to try different size of sprockets in my bike. I think (I am not sure as Ihave checked) i have a 22 tooth now in the front and the machine won't take revs over 4500 with fifth gear and also chokes on climbs and facewind. No power. Fastest speed this year is about 115 km/h, down hill, backwind and the sun behind me.

So maybe a smaller front sprocket will help a bit. Also the aftermarket silencer is s**t I think.
The problem for me is to find a store which sells the sprockets. And to know if the ones for 250 fit the 251?
Thanks,
Teemu