Originally Posted by tgaydos
Dave where did you find that air filter adapter?
The air filter adapter is from a Yamaha pw80, it slips right onto the 18mm mikuni carb I'm using here but won't fit the stock nt or speed carbs unless you make an adapter to fit this adapter... it'll fit on the mikuni vm18 perfectly like in my pic and it also fits the cns carb, and of course, the pw80 carb. I don't recommend using a cns carb on these due to how finicky they are to tune and they leak like crazy if you don't have the right intake...
The best carb for these engines is the NT or the NT Speed carb unless you're doing some more serious engine mods, then the mikuni vm18 becomes a good choice, and so are the Dellorto phbg 19 or 21mm carbs, these are a bit trickier to tune but will offer better acceleration and top speed. I was going 43mph on my mountain bike with a stock NT carb and 44 tooth rear sprocket so don't underestimate the stock carbs either... the larger carbs really help the acceleration once some porting is done and will allow for more top speed, just switching from an NT to an NT speed carb will give you another mph or 2 if you got decent porting and a good exhaust...