Thank you for your input Olderdan and PJs. Yes I aggree the needles and jets wear but then again are simple and economical to replace, The wear in the slide bore occurs at the most common throttle setting, in other words at cruise. The result is that the wear in the slide is not uniform. If you were to look at it cross-sectionally there would be a belly in the bore towards the middle. The wear is inline with the air flow as the slide jiggles and vibrates in tandem with the engine. The result is you end up with what is commonly referred to as a flat spot in the bike' performance due to the air leaking around the slide rather than via the slide cutaway as the fuel is no longer being properly metered. At idle the bike still runs properly as it is being supplied through the pilot circuit and the slide is seated at the bottom of the bore. Similarly at wide open throttle the slide is now wide open and past the wear.
I trust this clarifies how the wear impacts the carb's performance.
thank you again