Advise on fitting throttle cable

Don't see why not although the YBR is fuel injected,there will be some mdifications either way.

Hy a have a 2007 yamaha yber 125 it starts first time but then cuts off after 10 seconds anyone know what this is am struggling

Hi ........... One tooth less will give you more top speed (if you can pull top revs) but will reduce accelleration. If you go for one tooth less you'll need to tighten the chain and/or remove a link. It's a trade off ............ decide what you want the bike to do.