CV carbs

[cxman]

43 odd years since the cv carb came out everyone has tried everything

and still no answer other than a cv carb needs the proper designed environment to run in

i have been watching and dynoing every kind of change and still not seen a magic formula

that is why i either leave them alone or swap em out

 

[crazypj]

Mikuni are much easier to deal with, the Honda's have 3 jet carbs which are really well engineered for stock setup but real difficult to work with when anything is modified

 

[ahm1]

Don't get me wrong I am convinced its the pods I just thought there is a way around it cause others have done it. I might build an airbox or go the mikuni route

Sent from my HTC One X using Tapatalk 2

 

[ahm1]

so would mikuni vm's be the go? also thinking of going single carb what size would i need for this 36-38mm?

 

[MR915]

Im not familiar with your carbs so i dont know if yours is adjustable but I've done a lot of reading about my cv mikuni's. i was having some bogging issues that I finally figured out was my petcock but also the midrange is controlled by the needles in most carbs, not the jets.
Refer to this:

I would recommend taking a look at throttle position when your having the issue and going from there. Plug chop if you can to see what direction to shim or move your clips on the needle

That chart doesn't apply to CV carbs. CV's are vacuum dependent so you use RPM range as opposed to throttle position.

 

[cqyqte]

Okay I have heard all sorts of negative talk about Pod filters and CV carbs here as well as PD carbs on the SOHC forum and frankly I have never had an issue when setting them up on any of my bikes. Now my idea of Pod filters vary somewhat from those I have seen displayed in the endless knock Pod threads, in that I use K&N filters as shown in the photos below.

The major difference is that the filters I use are taller (3 1/2" -4") of filter material height as opposed to the shorter oblong or round tapered filters of 1 1/2" tall. There have been many good explanations as to how the air flow in the shorter pod is too turbulent, or that the pod restricts important ports. When I constructed my '71CB450 I chose to run filters as seen in the first photo. I expected a difficult chore of tuning to get them to run right, but was pleasantly surprised to find that the bike pulls hard throughout the full rev range and the plugs are spot on for mixture ratio at plug chops on any throttle position. I fully expected to have to run with a 2" internal sleeve added inside the filter to extend the carb horn into the filter to create a more laminar air flow, but found it was not necessary. I am beginning to think more and more that with the short Pod filters it is the fact that the air is being drawn in from the side and then immediately is forced to turn 90 degrees down the carb throat playing havoc air jets, making them behave more like pitot tubes than their designed purpose.

I recognize that some of your projects cannot accommodate the longer filters, in which case I suggest you try to install a short internal sleeve of aluminium wrapped around the carb horn to extend it into the filter. This won't do much for resolving the air being drawn in at right angles to the carb throat but it will allow for the air to begin to flow less disturbed past the air jets and ports.

 

[cxman]

i would try twin vm30 or single vm34

 

[mydlyfkryzis]

The longer pods seem to work. the problematic opnes are those small, short Emgo Pods, and any pod that blocks the air ports at the mouth of the carburetor.

The V-Twin setup has long intakes, so that is not the same issue. Plus the ones you are using are longer. The little Emgos have very little surface area too, so are more restrictive than even stock air filters.

 

[crazypj]

The longer pods seem to work. the problematic ones are those small, short Emgo Pods, and any pod that blocks the air ports at the mouth of the carburetor.

...............................and any pods on 3 jet Kei-hin