paishy

I have a yamaha tzr 2rk UK spec all standard, the UK spec model came with a fixed reed valve, I have fitted a servo kit to it (bags of fun) few problems will list below if anyone can help with them also will to pay for work to be done. Problems. 1. It bogs down At about 4k for a few minutes then cleans itself up. 2. The spark plug gets black and coated in carbon. 3. As it's a UK spec and I have fitted the servo will I need to change the jetting on the main jet and/or pilot screw if so what to and do you know the settings. 4. I think someone has played withbthe 2 stroke pump and changed how much it sucks through per strike. Could someone tell me how to check and how to put right for the power valve

Heya guys and girls, proud owner of a very old yamaha tzr 125 2rk 1988. Almost on a full restore just got to do a few tweaks.