sr 125 k reg noisy top end & lack of power

hi i am a bit of a newbey to the sr and would like some help i have just got a k reg with 33k on the clock the top end is a little noisy eg tappets or timing chain so any info on how to adjust would be good also the carb has been replaced so i would like to know what the jets should be and also if the carb bore should be round or in a kind of a figer eight shape or is this how they restrict them also wht the normal top end it as i can only get about 45 on the flat but i am a self confesed fat git (17 stone ) any help /tips on keeping this bike healthy would be good thanks kev