Yamaha rxs 100 can anyone help its been fouling up spark plugs and doesnt bulid up the revs smoothly ( build up the revs and it pauses ) can anyone help please thanks

1) Is the choke stuck on? Solution: spray carb with WD40 and make sure it moves freely when you pull the choke on and off.
2) are you using the correct 2T oil? It may be that it is pumping too much oil through. TIP: Take out plug and look at colour. if it is brown/tan it is ok. if it is white then there is not enough fuel going in. if it is black and sooty then there is too much fuel (choke stuck on) if it is black and oily wet there is too much oil (adjust the oil pump as per handbook)
3) Could be ready for a decoke. How many miles has it done? Solution: REDEX teaspoon down spark plug hole, turn engine on kickstart with ignition turned OFF. Wait a few mins and start up bike as usual,a few revs should chuck out loads of smoke and clear its guts out.