I'm not sure how you know what their intent is regarding the illustration, but I gather you're saying that by the third image the idle circuit flow is still at max though diminished in ratio to the primary circuit. And yet the main jet is centered within the venturi, and the slide contributes to the venturi cross-section. Meanwhile the idle circuit exit orifice lies downstream of all that, after a step to an increased diameter in some carburetors such as the CV Bings... this step-out equating to a diffuser and therefor lower velocity air at that port (in relation to the venturi)... which I believe to be lower in velocity than that registered when the throttle plate is nearly closed and essentially creating a temporary, local venturi at the idle circuit exit. Getting back to what you're saying, the idle circuit is and has been at peak flow from part to full throttle? Is it not designed to operate most efficiently at idle? For clarity, let's keep this within the context of a running engine.
Of course the idle jet continues to flow fuel particularly at small throttle openings. At low speed cruise you are riding on the idle jet. Look at the size of the damn thing. I have a 123 main jet and a 45 idle jet. That idle jet is big enough to run the engine on it's own at low speed cruise when the engine is only producing a few HP. One factor which helps the idle jet to continue flowing fuel is that due to the inclination of the carbs the fuel level is higher for the idle jet than it is for the main jet and therefore the fuel has to be lifted through less height. Probably a gross over simplification but I always thought this diagram of fuel flow nicely illustrates that total fuel flow is a summation of the idle jet and main jet. https://www.dropbox.com/s/v68zj2njddbhkce/Pilot circuit fuel flow.png?dl=0
You are correct. As said, the "idle" or pilot circuit is active from idle through part throttle. The main system is active from part throttle through WOT. An illustration, from BING: --Bill
one HUGE advantage of Adv vs airlist is the amount of detail possible when folks decide to drill in. IMHO forums with huge traffic are the best source of detailed technical information available to anyone. yes there will be wrong information posted but if traffic is high enough. those wrong answers will be refuted and pointed out. one advantage of airlist is the very knowledgeable participants active. drawback is those very_knowledgeable folks are small in number and getting smaller as they fall to father time. it's easy to tell who posts high quality information ... all one has to do is looked up threads started for quality and by how often their posts are disputed. for instance Renner is not that active, but if you look up threads started. one will quickly see his posts are very high quality with loads of detailed info diving deep with clear pictures. so conclusion is Renner's posts are likely to be quality information that can be trusted. no one is immune from making errors, it's worth noting how folks correct those errors. for instance right after I pointed out Snowbum is not a good source of info for LiFePO4 .. naturally he immediately had an issue with that. after we communicated and and discussed in detail why ... he responded with an open mind and immediately added those technical details to his knowledge base. which I responded by withdrawing my statement by da bum not being a good source of LiFePO4. which was no longer true since he immediately improved his knowledge base. which made me respect snowbum's huge knowledge base even more.
And, from another Bing source: Says the same thing in a different graphical format. And you can even change the shape and character of the mixture curve for the "pilot circuit" by changing the Air Bleed jet or drillway, and even the number, size and arrangement of the holes in the Emulsion Tube. Carb tuning can be a can o'worms. --Bill
Guys - final warning, I'm tired of cleaning up messes in here. Keep discussions above-board, and refrain from personal attacks. If you want to troll people in to endless arguments just to belittle and berate them, take it elsewhere - either to JM or off the site entirely.
Those charts do not prove your point that the idle circuit drops out at a low throttle opening. Those charts show which circuits affect particular throttle ranges for tuning purposes. Get the difference? Just because the idle circuit dominates down low does not mean it's inactive from there on out. That's a faulty conclusion.
I found 190e's post #172 very helpful in describing the action in question clearly. _cy_, thanks for your generous comments. Thanks and I get that, though I gather your post is directed toward Bill, who may be trying to help me. I was out enjoying today's vintage ride and apparently missed a diatribe. And the consensus is that the idle circuit, after quickly ramping up, remains at max flow throughout the remainder of the throttle range. Regarding the third image in post 151's illustration, the idle orifice spray is drawn so faintly that, on my screen's resolution, it can hardly be seen without getting my nose up to it. So I see. My apologies for my part in mucking-up the thread. I would find it very interesting to actually see the carburetor/fuel delivery in action. taken today, not my bike:
Renner now you are really trying to confuse folks that's a dellorto without butterfly and a powerjet that works completely different from a CV carb like Bing. would be a shame to lose this thread to JM as I'm getting ready to drill in on late model Bing CV circuits and how to trouble shoot ALL the circuits without taking main jet assembly apart. here's my R90S serial #0041 in what I believe in original unrestored condition (new petcock/hoses) with now 8,300 miles .. ah the mystery of the black R90S engine ....
Probably not the right thread for this, but.......none of the R90S's came from the factory with black cases. None. Someone painted that engine and trans black after it left the factory.
OT yup .. that's why it's a mystery .. all indication are that this R90S was picked up from our local BMW dealership, Atlas cycles as is. based on what little remaining documentation from that era, Butler & Smith were known to do a bit of R&D. for instance here's an early B&S ad for 1974 R90S that claims 77hp .. it's not that hard to achieve 77hp from a 900cc engine. this is where we need someone like Oak from Airlist for a history lesson.
Yep, the dealer may have painted it per a client's request. When I worked for a dealer in the mid 70's, we'd get all kinds of crazy requests from customers. I ended up with a huge stash of NOS take-offs because of them though, so I'm grateful!
And if you want to get to the bottom of it, CV carbs are a UJM contribution to the genre, whereas slide-valve carbs are the only proper ones for a motorbike... No argument, just philosophizing... :) --Bill
Just to continue the off topic theme of R90s paint This is apparently a faithful repainted of an R90s paint scheme. BMW park lane had 3 or 4 R90/s painted in alternative colours just the brighten up the early 70s