Redesigned OEM Air Box
 

https://cimg1.ibsrv.net/gimg/www.sup...d91135ef13.jpg
https://cimg9.ibsrv.net/gimg/www.sup...ebfdd825aa.jpg
https://cimg4.ibsrv.net/gimg/www.sup...65addba3b7.jpg

How about a few words of description.

Sorry, I did not want to bore you with my description....I thought the pictures would paint my thousand words....but here goes;)


https://cimg2.ibsrv.net/gimg/www.sup...377df297a1.jpg
I wish I knew how to reduce the size of the Pictures....anyway Picture 1 of standard Air Box which would have two different style of Air Funnels which I used to call "Trumpets".....(old school)...and the tubes going to the collector box coming from the Breather hoses from the Cylinder Head Cover.

I forgot to mention that I went on Ebay to purchase another Air Box, which came with a bonus in having a K&N filter. I cleaned the filter and re-sprayed it with the filter oil.
I cleaned up the Air Box with a small Dremel to give the carburetors a clean intake as possible. At the elbows which go to the breather hose from the Cylinder Head Cover, I carefully removed the two plastic pins that holds the elbow in place and replace it with straight plastic tubes which I got from my Koi Pond fittings. You can only do this modification if you have a Koi Pond...:D These tubes were epoxied in place, once I found the correct height needed to go through the plastic into the K&N air filter. Now I installed the cover to the Air Box.
What are my thoughts on this Redesign....?
My first thinking is, that there is a lot of Crank Case pressure, which is involved in this engine. Both pistons will travel at a staggered time upward and downward. I have also removed the "Secondary Air Supply System" and blocked off the "Pair Check Valve". Whether this reduces (when in use/installed) the crank case pressure I am not sure....all I know is that there is quite intense amount of case pressure which could effect the carburetors efficiency.....so I vented the Cylinder Head Covers above the filter and placed the Air Box cover on top to keep the fumes contained. Now being a K&N filter, this is not a problem to clean....probably more frequent than normal...but this is my Track Bike ("Bird of Prey") and I am thinking of designing a small style of diffuser on top of the tubes that go above the air filter. All I know, just taking it down the road, it seems very...very...responsive.
And that's my story...

By the way...This engine has Stage II Yoshi Cams, High Compression Pistons, Lightened Flywheel (by Eric) and the standard carb changes with Jack Flash's pilot screws...they are great.

I can't believe you still use such a restrictive filter on a track bike?

So, you have the crankcase breather lines now routed before the air filter? I thought it was best to have as much vacuum (negative pressure) as possible to keep the pumping losses down? Wouldn't placing them upstream of the air filter be going in the opposite direction? Or maybe I missed something with what you are doing here.

Back in the old days, when I was building and dyno testing race engines, I found that a "clean" and "properly oiled" K&N flowed pretty close to no filter at all. I chose to run the K&N to keep small birds and rocks out...Road America in the late 80's heading into Canada Corner during an EBC Endurance Race, a bird made it into my intake tract...While quite a mess, we finished the race. "My habits protect me, but may assassinate you." -Mark Twain said that.

Ah cool :-) Yeh I found in the early days (80's) that a good flowing filter/s required no different jetting to no filters at all.

You have my mind working overtime on this matter now (engine negative/positive pulse causing havoc with the carb slides), my Wife will be pissed with me, laying all night thinking about this ;-)

Hey Jamie
That was a concern of mine as well, regarding the engine crankcase pressure, so I do install the top cover of the air box filter. I have seen pictures of a box in a location front of the air box area handling the crankcase fumes with the Mori Carbs....so I went with a less of a radical move and used existing stuff..as I am a low budget person. I figured with all that crankcase pressure, it must have some effect on CV carbs....so I was trying to give the carbs the least amount of turbulence as possible from the engine. This is why I mounted the breather tubes above the filter with the air filter completely covered as normal. I will be back working on the bike when the good weather comes......I hate the cold. (from Bermuda)
I hope this explains what I was thinking.
Later....