You will need to seal the fuel bowl and re vent it to stop fuel covering the air jets on downhills as the weber works best on "backwards" you will also have to set the float correctly. They do have problems but a hell of a lot cheaper and easier to rebuild than the stock carb and has a big power increase. I ran mine for years without do anything other than unbolt it of a cortina at the wreckers and bolt it straight onto my zook backwards and was happy but now Ive been fine tuning to get even more out of it. If you want some more info got to
www.zuwharrie.com and search webers and read anything by sarge he is an absolute wiz on these things.
Nik