Hi there I’m looking to get a better top speed on my 2008 Yamaha yzf r125 it’s got a couple of bits done to it like  straight pipe sports exhaust upgrade brakes but wanna get the most out of my engine it’s got a rev limiter at 10k revs and just want to fully derestrict it 

'Sigh' 

Still with the restricted myth.

back in the 80's and 90's when the learner rules came in European bikes were not affected. Due to the learner uk market being small they just castrated the 20-30hp euro 125's for the brit market. the brit teens, me being one at the time. Promptly ripped out said restrictions and got 80% of that power back.

Modern 125's like the YZF are not restricted at all. The emission and noise regs they have to pass mean they make the hp they are designed to. You can throw a fortune at it and get a few hp but not enough to shout about for what it will cost.

Spend the money on rider lessons, knowing how to brake and take a corner will make you much faster than an extra 3 hp.

Have been looking up on the bike a lot and looking init a 150 kit on it and a bigger front  sprocket to make it a higher gear ratio what are you thought about that but I don’t want my bottom end to go ?

My thoughts...pass your test and get something bigger that your insurance company know about

I have to agree, makes a lot more sense than f#cking up the bike you have. 

Sorry I know its not the advice you were hoping for but that's the best advice honesty.