Lose the airboxes. Use air pod filters

[Chris Cochran]

I mentioned the use of air pod filters mostly as a side-thought in another posting that I have in the Tech Tips section, but thought why not throw the thought out here as a stand-alone thread where the idea may get more attention?

Pray tell what would you in the "tribe" think about dumping the air boxes and going to four air pod filters, instead? It apparently does not seem to be a popular modification although there is a lot going for it. Several thoughts, pro and con, about this idea come to mind, in no particular order of importance:

1) The idea of the loss of physical carb support on the air intake side of the carbs immediately comes to my mind. I've recently seen pictures of a bike for sale that has this modification and while it looks cool as sin, and would seem to make things a lot easier to work on (Re-installing the carbs would be a LOT easier. No more dealing with spring retainers rolling around the rubber connecting tubes. No more worrying about poking holes in those tubes. No more fighting to get the carbs even in the bike at all.), I would have to wonder how much "bounce" of the bike it would take to have the carbs pop out of the forward rubber mounts. Unless:
1A) Perhaps the lower air box could still be retained, without the four rubber hoses, for the simple reason of providing the air pods something to press up against for support purposes.

2) How sensitive is this engine in regards to any air box modifications or removal? Would doing this result in any loss of torque, etc? I've read about the Vulcan 500 being extremely sensitive to air box modifications. It basically runs like crap if anything is changed with its' airbox from the factory configuration.

3) Would using air pod filters require a jet change? I wouldn't think so but..... don't know.

4) Riding in the rain might be an issue. Yet for my dual-carbed 750 Vulcan the switch to air pods is quite the popular change. I've not read of anyone complaining about having problems in rainy situations.

5) I wonder if the engine would be any unduly noisier.

6) Lastly, how could one attend to that fat hose that plugs into the right side of the upper airbox? I don't know what that hose does so how would things be affected if that hose is blocked off?

[SgtSlag]

The XII uses CV (Constant Velocity) carbs. In 1979, Honda introduced CV carbs to their infamous CB750's. I owned a 1979 CB750K, with such CV carbs and a unique OEM air box (irreplaceable -- some myopic owners got rid of them, and could not find replacements!). One CB750 forum member worked, and worked, and... On re-jetting his carbs after he installed Pod Filters, removing the OEM air box. He always had a flat spot which he could never eliminate. Another guru forum member laughed at him: he had tried, and he had never heard of anyone overcoming the flat spots in response/throttle, though many had tried; they could move the flat spot, but they could never eliminate it.

The guru's stance was that if Pod Filters offered better performance, the Honda Engineers would have installed them, at the factory. I agree.

The XII's are in a similar boat. The Kawasaki Engineers knew what they were doing, better than any amateur, anywhere. They chose the best compromise they could make. I was/am happy with their results, both on my old Honda, and on my XII.

If you plan to go down that rabbit hole, be prepared to rifle through jets, time, and money, for questionable results. Cheers!

[Chris Cochran]

That answer works for me. Thanks. If it negatively affects the machine operationally, it outweighs any ease of installation hassles.

I never planned on changing my 750 Vulcan, so I won't change the Voyager, either.

[Conrad]

+1 on the tuning/jetting issue. My experience with CV carbs is that when tuned correctly on multi carb multi cylinder engines, they work great. But they are quite touchy to airflow/vacuum changes, and can be a real bugger to tune once something changes.
As far as the original engineering involved, my experience from 40ish years of wrenching on nearly everything with wheels and lots of things without, also as a machinist dealing directly with engineers on a daily basis, is that one thing engineers tend to do is make things WAY mor complicated than necessary.

[Z1kawasaki fan]

In most cases people will go to the pods to increase airflow for performance upgrade, but the increased airflow also requires jetting changes.
Another problem with the pods is the turbulent air flow around the pods with the inner two having less air or a different amount of turbulence. The airbox creates a uniform air supply equally distributed to all four carburetors.
It boils down to personal preference and what your performance goals are.
I had a 1975 Z1 that had pods on it and it did create some less than ideal situations for normal riding.

[Van Voyager]

I had a 1975 Z1 that had pods on it and it did create some less than ideal situations for normal riding.

That 75 would have had direct lift carbs, right? It's the CV carbs that PODs cause never ending grief.

[Nails]

This topic has been discussed before. Search on “pods”. CV carbs, specifically the circuit that lifts the diaphragm, requires laminar air flow, which generally requires a large air box. Or two.