look at my poject yd 70 thread.
1:Filter is must. (use pod filter and the elbow of new cd 70 euro2 bike .. i had a seperate thread for this some time ago) .. i am still running that filter for the past 4 years.. cost 150rs .. just clean it with petrol 2-3 times a year.
2: for carb use either qingqi pz22 . (very agressive power.. hard idle. but its for power and reasonable economy 45-50kmpl.. @ 55-60kmph. or a honda cd 100 genuine one pd22 very soft smooth and good idle but bike wount be as powerfull as on pz22.
3:for silencer it does improves performance. i had used a qingqi cd 100 vender silencer not too loud.. but awesome sound and performance.
after i pused reply i noted this is very old thread..hope this share is of some benefit to someone..