Well, unfortunately, I am rather limited in options for throttle bodies. They essentially have to come from sport bikes, and it appears that my floor is going to be 38mm (+6 from stock, +4mm over stock NH750). Now, I know with carbs there is a certain need for the smaller diameters, especially CV carbs: the velocity of the air moving through the venturi is what reduces standing pressure and both draws the fuel from the bowl and on a CV carb positions the slide properly to operate the needle.
Typically for a car, the carbureted version will have a slightly narrower throat than the fuel injected version: for instance, the 1.8 VW engine came with a single 38mm Weber OR with CIS you had a 40/30mm progressive throttle body. I think I can definitely rule out the CBR TBs; I don't think I want to go for 40! But I also feel that I should be reasonably fine with the 38s; my big worry was that moving up was going to cut into my throttle range, giving me an On/Off switch as you can find in high end, high strung bikes (Where I'm seeing BIG TB sizes, 42, 45... 48mm... PER CYLINDER). With you folks letting me know that my response might actually suffer with too big a body, I feel I'll be pretty safe there. I will still have the port size restricting air flow, and I'm not messing with valve sizes, so... we'll see how this goes. If it runs like crap on the 650, I'll swap the 750's carbs over and give them an extra 100ccs to work with! :p -Kurt On Sat, Jun 30, 2012 at 3:15 PM, zgotts <zgo...@hotmail.com> wrote: > Agreed, increasing carb diameter will give you crap response at low revs. > The incoming air wont have enough velocity, so mixing in the cylinder won't > occur as it should. Won't do much for top end either at the NH's low 9k > redline. Dont mess with it! > > -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to nighthawk_lovers@googlegroups.com. To unsubscribe from this group, send email to nighthawk_lovers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
