I don't see it either... but that's because I hear a very different and more logical explanation.I have a very hard ime believing stock air boxes create a "vacuum" need for the bikes to run properly.
Um..carbs work off pressure differential. If both sides were under vacuum what would draw the fuel out?
Edit: the above was not directed at you, Seb. I just keep hearing " the factory airbox creates the needed vacuum for the carbs to work properly. " I dont see it.
I agree on that. With pods on CV carbs in particular, there seems to be a common problem that some poorly designed pods have weird airflow patterns or even actually block off a bit of the rim of the carb intake. This means air pressure often goes to shit right where the channel that sends air to the slide lift is. Putting the pods on the ends of correctly fitted velocity stacks should avoid that, but most people don't bother... while most stock airboxes effectively have (flexible) velocity stacks as part of the design, namely the carb boots. Good airflow patterns are probably the main purpose of an airbox, making engine tuning easier mostly due to the boots and the creation of a source of non-turbulent 'dead air'. Getting rid of those boots also effectively changes the intake track length, which may further alter tuning. The resonance effect is just a further tuning trick that an airbox happens to allow, and probably only adds a few percent to HP at the specific RPM it is tuned for. Still, a few percent HP to put on the spec sheet, with effectively no weight penalty, and a manufacturing cost equivalent to a decent tupperware container; you can see why almost every bike comes from the factory with one. A notable exception would be all the HD's out there...All bikes have trumpets, velocity stacks, etc. of some sort in their factory air box configuration. I think it's shitty air entry that causes the issues, not the fact that they no longer share a common plenum.
I've got some ideas on this, but so far, no time to build/test any of them.
Owning a twin cam CB with stock CV carburetors and pods makes me the poster child for a non pod - friendly bike. I really wanna do some experimenting on this.
Yeah, some people claim that's the problem, and that they have fixed it by either altering the pod not to block that port, or altering the carb by drilling a hole from the carb throat into that passage. I dunno, but I suspect results are highly variable depending on the carb and pod in question. In theory there's no reason that it shouldn't work if you can ensure a good even airflow to the entire carb oriface... in practice, airflows can turn into a turbulent mess for no obvious reason. If I wanted pods on my carbs, I'd put my money on having pods at the ends of velocity stacks, or something similar.I thought the whole problem with CV and pods was the fact that the rubber boots on the pods block the little air passages around the mouth of the carb? Like the idle circuit..... I think that's what its called then you have the humongous one that I think operates the slide right?