stijn1990 wrote:I am going to put a K&N air filter in.
Do you want it to go slower, make more noise or wear out quicker ?
Now i may be wrong 'cos i don't know the Yam but most 125s cannot easily be "souped up" 'cos they are designed to be the power they are.
Think your MT125 is already 15bhp so that puts it head and shoulders above most (not all) current 125s in the UK market. It will be a pretty quick bike as standard. With nice well sorted FI and electronics designed to work with the OE air box.
Don't do it
Spend the money and time on hours on the road and/or training, that's what will make you faster (if that's your aim)
Just my view