I've scanned thousands of custom CB750 images such as Googling "cb750 cafe" and almost without exception, the bikes are running either stacks or pods. The majority are pods and most seem to be built by competent builders. Is the difference between "acceptable" and stock pretty minor if even noticeable by most? I have no experience whatsoever and I'll be running a 4-1 mac with pods and jetted to 120 to start. I would think that if the bike runs that terrible with pods then either nobody would run them or someone would have come up with a better solution by now. I've read the pod threads at length.
I caution you.
I am not a fan of pods for the average joe who doesn't have the facilities to test and prove the design change that is PODs.
How many of those Googled pictures of "cafe" you found, had people riding them?
How many of those Googled pictures of "cafe" you found have any performance numbers tied to them at all?
How many of them got the same or better fuel efficiency? (The ones that don't care about efficiency generally don't care about performance, either. These people have gained nothing with the "cafe" mod, except a photo op.)
If you have access to a dyno, or a test track, can read spark plug deposits, (or are phenomenally lucky), you can make pods work as well as the stock arrangement, if you spend enough time at it.
Carburetors are simple, but have many facets to adjust.
The main jet size
The throttle valve diameter
The throttle valve taper angle
The emulsion tube air bleed holes size
The emulsion tube air bleed holes count
The mains air jet size
The pilot jet size
The pilot air jet size
The pilot emulsion tube
The pilot emulsion tube air bleed holes size
The pilot emulsion tube air bleed hole count
The throttle valve cutaway height
Some carbs also have an accelerator pump to augment some of the above and mask their ill effects.
Engineers for the stock induction have tweaked each and every one of those parameters to gain best power AND a modicum of efficiency for the stock configured engine.
How many of the bikes pictured from a google search have done that. How many of the Googled bikes have even been driven farther than around the block before it was "done". (...and ready for sales.)
Here is what I believe is typical. The beautiful stock air box (snicker) is replace by the cheap and ugly pod filters. Engine runs like poo. This should be the first indicator that you F'd up. But no, everything else must be re-tuned to compensate for those cheap ugly pods. Therefore, without any real understanding of how the carb operates or what the engine needs are, huge mains are installed (It's really about cosmetic appearance, after all.) This makes the carbs sloppy rich in the 3/4 to Full open throttle range. The engine "seems" to run a bit better. The throttle valve remains set lean to partially compensate for the big dump of fuel leaking past the main. Somehow, the rider spends enough time alternating between WOT mid and low throttle to keep the plugs "clean enough". The bike never has the fuel efficiency it once did with the stock air induction (so the owner never mentions that aspect again).
Another repercussion for non-accelerator pump carbs, is throttle response stumble/wheeze. The pilot circuit is tuned slightly over rich for idle speed AND throttle response. Part of the tuning job springs from the expected vacuum level in the carb throats. This is what is pulling the fuel through the jet orifice from the local reservoir (float bowl).
Shortening the inlet duct reduces the vacuum level, causing a lean condition. Also, and depending on the brand of pod chosen, the total filter membrane area may be increased. This creates a lower differential across it, which ALSO lowers vacuum pulling at the fuel from the pilot jet. These factors add to starve the engine of fuel when the throttle is suddenly opened. Since the oversize main and throttle valve jets are leaky, some of the throttle response is sort of compensated for, again at the price of lost efficiency.
How many of those Googled pictures had dyno charts, or a 3rd party tester that could accurately describe the street performance of the pictured bike?
We on the forum, have read many reports of podded bikes running great! Only to find out they only really checked it a 60 MPH with a short blast to 80. I can count on one hand the number of dyno results I've seen here involving pods. And those invariably were with modified engines, some of the them highly modified.
There is no way I will believe pods create power. They are a cosmetic change to the detriment of a stock engine's performance envelope. They make more noise, and some equate noise with power.
Anyway, there are few "complete" builders. A competent painter doesn't automatically know how to tune carburetors.
A competent welder or metal smith doesn't automatically know how to tune carburetors.
A competent assembler of parts doesn't automatically know how to tune carburetors.
A competent rider or buyer doesn't automatically know how to tune carburetors.
Some or all of the above may not even WANT to know how to tune carburetors.
After pouring in a lot of time and money into a project with the primary goal being the way it looks, how much added tolerance to "runs terrible" will there be? Especially when the realization occurs that the last 10% of the engineering takes 50% of the time?
OK. Pods may look good on a stationary bike. (Kinda like saying an exposed kidney or liver is attractive. Are external gills attractive? (see attached)) But, you don't even have to put fuel in the bike to get that nice picture for google to find.
I venture to guess that 80% of the owners of pods don't actually know what they've done to the engine performance and efficiency. (And, I don't mean just MPG. It is how much of the fuel expended results in HP to rear wheel.)
To me, knowing how well that beautiful air box works and melds so well with the carbs, makes it all that much more attractive for a machine that will actually be ridden and serve a purpose besides a photo op.
Cheers,
