so....no on really knows exactly why Haynes applied this Mikuni factory check to Keihin carbs. There are literally no specs from Keihin on how to do this. Suffice it to say that the Keihin carbs on sohc4 bikes work basically the same as a Mikuni VM series carb that you would find on a Kawasaki, Suzuki, and even some Yamahas, and someone decided you cam use the same specs. So you are looking for a fuel level of 4mm + or - 1mm measured from the float bowl gasket surface. I have used this method many times and prefer it, especially on carbs where the float has been tampered with perhaps a few too many times. On carbs such as these you may find that even the carefullest of float measurements results in differing amounts of fuel in the bowl. So, given the spec of 4mm + or - 1mm, a difference of 2mm is gonna make a change.
