I've been reading some books which discuss historical development of carb design (e.g. Carl Shipman, John Robinson) and the following thought occurred to me:
All modern carbs have an air bleed which feeds air to the tube surrounding the needle jet. There are 2 flavors: "primary choke" and "emulsion tube", but that's not relevant to my question. The main purpose of this air bleed is to compensate for the fact that venturi depression increases non-linearly (square?) in relation to throttle opening. Without the air bleed the mixture would be way too rich at WOT. It seems to me that adding an air screw to this air bleed passage would be an easy way to adjust mixture strength throughout the throttle opening range. Maybe not as precise as changing jets, but certainly more convenient on the trail. This proposed bleed air screw will be more effective at larger openings, and you've already got the idle circuit's air screw to compliment it a small throttle openings. Seems like a good feature to have on say, a 2-stroke carb. Yet most (none?) of the 2T carbs have it. Why? Carb designers are smart people, so there must be a reason for this. Can anyone enlighten me?
Posted by: blackduc98
Come on now, none of you gearheads have an opinion on this?
Posted by: DaddGoneMadd
I may be wrong, but I think that the Keihin FCR four stroke carbs have this provision.
Posted by: kylee
[QUOTE=blackduc98]I've been reading some books which discuss historical development of carb design (e.g. Carl Shipman, John Robinson) and the following thought occurred to me:QUOTE]
Titles, please?
Posted by: Filthy_McNasty
I think the engineers have it right. More adjustments is just more for me (and most people) to screw up and get wrong...
Posted by: GPracer2500
Quote:
Originally Posted by kylee
Titles, please?
I'm guessing
Motorcycle Tuning Two-Stroke by John Robinson
and Motorcycle Tuning for Performance by Carl Shipman
Posted by: blackduc98
Right on the money, GPracer.
ISBN numbers are: 075061806X and 0912656131
They were available in my town's public library, so I suggest you look in yours before trying to buy them, since out-of-print books can be very expensive.
