Originally Posted by Sporting Wood
The restriction in the airbox is the snorkel at high rpms. Bigger mains fix this, and are absolutely necessary using the airbox and even more so without. The first jet you set in tuning is the main, and its done at wide open max rpm. All the others are adjusted down to accept the larger main...This the difference between properly tuning the carbs and not.
My experience with the 950, which is extensive, indicates there is absolutely no difference between front and back, temperature, egt, o2, etc... I have ran 170 mains front and rear in the box for 5 years. My bike is jetted near perfectly, outruns every other buddy with a 950, and returns 40mpg. o2 from either cylinder always registers between 14 and 17.
I just made a filter like these, not the cpr, but the same filter element on an aluminum baseplate, and am starting with 175 mains, tweeking the bowls a touch leaner by lowering the floats. These carbs tend to have an annoying tendency to suck fuel from the main when it should be drawing off the slow, so compensating adjustments must be made with the float and the screws. My floats are already a mm leaner and my screws are at 2 turns. Another half mm and a half turn in might do it but I'm running it to evaluate first.
To the op, if your swapping from the h2w prefilter jet setup to this, don't forget to swap your airjets back to stock!
Interesting thoughts....but why do you say that the snorkel restricts the airbox? The inlet snorkel surface area is clearly larger than each individual carb inlet. Also, the 990R can happily put down 110+bhp with an identical airbox-snorkel.
Also, what problems do you expect if the H2W base jetting (plus larger mains) is used with a CPR filter?