I have a 2005 kawasaki KX125 and I was wondering if anyone knew the modifications I would need to make to make it road legal.

thanks in advance

wild guess here but i'd think, headlight with dip & main function, red taillight with brake light too, as far as i know you don't need indicators to ride on the road. it'll need tax and insurance too, is it registered? if not you'll need to apply to the dvla for a log book. hth

Not 100% on this, but new bikes require indicators & at least a R/H mirror-i'm sure the school i used to work at got a memo to that effect.
dont quote me tho...

I'd agree with the above, you'll also need a rear reflector for the mot,a quietish exhaust and a horn.
See if you can find specs for a pukka enduro bike, they'd only have the minimum requirements.

You don't need much. A horn and a speedo really. You can get a "daytime mot" on a bike without lights - obviously you're only allowed to use it in daylight hours though. No headlight, no tail light, no number plate light, not even a brake light (surprisingly) or so I'm told! Mirrors and indicators are optional. Any lights fitted must work though.
If you want a full MOT you need headlamp with full / dip beam, tail light, numberplate light, brake light operated from both front and rear brake, rear reflector, horn, speedo. Also road legal tyres on a crosser, and a suitable exhaust. It's a lot of work and you may be better off buying a road legal bike instead.