TOPIC:

So the filter box for my KZ440 LTD is broken. I'm thinking of building a custom intake setup and was wondering if anyone has done something similar OR has insight for my idea.

Basically I want to connect a 42mm ID silicone hose to each carburetor, with a pod filter on the end. Then I want to add a smaller "bridge" hose in between the two 42mm hoses in a sort of H shape. My logic behind it is that will help equalize the airflow/help with vacuum. 

 

Opinions?

Seems like that would add turbulence to the incoming air. Also, one filter will flow more air than a carb can use, so I do not see the advantage of adding more flow.

Kz750 twins have a hose connecting each intake but it’s behind the carb on the cylinder head side. It’s just a hose that connect the two vacuum ports that you use for syncing the carbs.  

this guy made his own air box
kzrider.com/forum/3-carburetor/599569-custom-air-box-for-kz440
 

Back in the day, I had an XS400 Yamaha.  The stock air filters were quite expensive, so I bought two cheep uni pods, and clamped them onto the stock intake runner tubes, in a configuration much like you reference.  The bike ran fine.  Much better in fact than with the pods attached to the carbs.  That was a nightmare.  

TexasKZ wrote:

Seems like that would add turbulence to the incoming air. Also, one filter will flow more air than a carb can use, so I do not see the advantage of adding more flow.

I was thinking it would help with the whole vacuum issue people talk about. Good point about the filters allowing to much air though. Maybe I can come up with some sort of Y pipe instead.

DoctoRot wrote:

Kz750 twins have a hose connecting each intake but it’s behind the carb on the cylinder head side. It’s just a hose that connect the two vacuum ports that you use for syncing the carbs.  

this guy made his own air box
kzrider.com/forum/3-carburetor/599569-custom-air-box-for-kz440

 

Ahh that's very interesting. Its too bad these CV36 carbs don't have that option otherwise that would make this super simple. 
I did see that airbox post, pretty neat. I just want something even simpler/lighter.

Nessism wrote:

Back in the day, I had an XS400 Yamaha.  The stock air filters were quite expensive, so I bought two cheep uni pods, and clamped them onto the stock intake runner tubes, in a configuration much like you reference.  The bike ran fine.  Much better in fact than with the pods attached to the carbs.  That was a nightmare.  

Yeah basically from what I'm seeing the CV36 carbs need that intake runner spacing to work properly. I guess it just comes down to needing the bridging hose or not.
 

My personal opinion is that the bridging hose is an unnecessary complication with no tangible benfit

Try it out. Take notes.
Change the pipe size. Take notes.
Remember, the carbs don't just suck. They blow too.

I used an oscilloscope to balance my carbs 2 weeks ago.
The pulses at the carburetor look like a sawtooth pattern.
Alternating between vacuum and pressure.

I guess i should put the pressure sensor in the airbox to see what the pressure/vacuum looks like on this side of the carb.
It's probably more subdued as it's a larger mass of air.

More testing I guess.

 

F64 wrote:

Try it out. Take notes.
Change the pipe size. Take notes.
Remember, the carbs don't just suck. They blow too.

I used an oscilloscope to balance my carbs 2 weeks ago.
The pulses at the carburetor look like a sawtooth pattern.
Alternating between vacuum and pressure.

I guess i should put the pressure sensor in the airbox to see what the pressure/vacuum looks like on this side of the carb.
It's probably more subdued as it's a larger mass of air.

More testing I guess.

 

Now that is some quality data

Just to add more info for those interested, I have found this article of interest. It addresses both intake and exhaust modifications and how some improve things and how some do not. I am not claiming it is the end all for either intake or exhaust changes but rather I found it of interest.
bmwmotorcycletech.info/InExTuning.htm 

Below is the XS400 Yamaha airbox runner configuration.  Other than length of the runners, very similar to what the OP is proposing...