TOPIC:

loudhvx wrote:

richard wrote: Anyone who says they can set up CVs has no idea how good the stock set up WAS

Or maybe they spent enough time and effort to know how to do it.

+1


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richard wrote: I get putting pods on CV carbs to look cool
But here it is,when you open the throttle with the bike off
The slide does not move..the slide only moves when the correct amount of air passes through
The carbs uper intakes,hense the name constant VELOCITY,this is achieved by an air box,filter
And small cut away in the box ,the engineers at Kawasaki didn't use a dart board do come up with
The dimensions to make it all work , a lot of science here
Anyone who says they can set up CVs has no idea how good the stock set up WAS

To illustrate how CV carbs work see:

Notice at time 1:20 when the throttle is opened the throttle vacuum passage opens and the throttle vacuum passage retracts. This causes the throttle slide and jet needle to rise. The amount of air that is drawn through the main intake is critical in that the more air drawn through it the less vacuum is available at the throttle vacuum passage which in turn affects the movement of the throttle vacuum passage. At time 1:56 with the throttle wide open the vacuum at the vacuum passage pulls the diaphragm and jet needle all the way up.

As I see it the difficulty in getting pods to work well on the CV carbs is dealing with the fact that the resistance to air flow through the main intake is reduced which in turn reduces the vacuum available to pull the diaphragm up. Consequently, tuning the carbs so the engine runs great at wide open throttle will normally be detrimental to the way the engine runs at other throttle openings and vise versa. This may not be of any importance to a person using the bike on the track since he will not necessarily care about how the engine performs at moderate throttle openings, but for street use this can be an issue. See
kzrider.com/forum/3-carburetor/585949-po...-a-free-lunch#585949 for extensive testing and dyno info.

Also here's an article quoting a Mikuni engineer who helped design motorcycle airboxes. Ed

In the early 1980's I was a poor college student commuting to school on an XS400. The stock air filters, one per side, were these large paper jobbies that were mounted behind the side covers, connected to the carbs via some rubber airduct tubes. Yamaha wanted a fortune for new filters so I bought some cheap UNI pods and strapped them to the carbs but no matter what I did to the jetting the bike just wouldn't run right. As a hail mary I reinstalled the rubber air duct runner pipes and attached the pod to the end of the duct. Amazingly, this little fix made a night and day difference in how the airflow entered the carbs and most of the running problems were miraculously resolved.

I have no idea if the KZ bikes are similarly affected but this little lesson learned over 30 years has stuck with me. CV carbs are very sensitive to how airflow enters the carbs, and simply strapping on a pod may not agree with the carbs in all applications.

650ed wrote: Congratulations! By removing the airbox and installing pods on your bike's CV carbs you have won the opportunity to become a carb expert. I'm pretty sure if you spend enough money on jets, etc. and enough time you will be able to make the bike run ok. Not as well as with the airbox, but ok. Ed

How relative to MIKUNI RS Series Radial Flat Slide Carburetors, designed specifically for use with pods?
Elaboration pleeeeeeeZ...

daveo wrote:

650ed wrote: Congratulations! By removing the airbox and installing pods on your bike's CV carbs you have won the opportunity to become a carb expert. I'm pretty sure if you spend enough money on jets, etc. and enough time you will be able to make the bike run ok. Not as well as with the airbox, but ok. Ed

How relative to MIKUNI RS Series Radial Flat Slide Carburetors, designed specifically for use with pods?
Elaboration pleeeeeeeZ...

Unlike the CV (constant velocity) carbs on the original poster's bike MIKUNI RS Series Radial Flat Slide Carburetors are not CV carbs so they are not dependent on vacuum operated diaphragms to lift the slides and jet needles. The RS carbs may take a bit of tuning to set up properly for a specific engine, but they don't have the same pod related issues as CV carbs. Ed

Thanks Ed, my interest is to use my RS Flat Slide carbs WITH the air box instead of pods, unlike the reverse application of using CV's with pods, which they WERE NOT designed for...

Mikuni's application literature specifies that the RS carbs are not to be used with an air box, and specifically instruct to remove and replace with individual air filters (PODS).