Not to compete with Mirko, he is another planet, but in my free time I've developed a couple of components for pure racing purposes, that are intended to be cheap hi-po parts for my CB750 in the first place, but I thought someone else here may be interested as well.
The first parts are pistons, with the help of a machinist friend we have perfected the art of transforming Kawasaki KZ650 pistons into high compressions pistons for our beloved race bikes. I've been using them quite successfully in the past, and now thanks to cruzinimage we can get the blanks at a very affordable price, they are available in 3 sizes 62, 62.5 and 63 mm (in my class I can go up to 63 mm diameter).
Upon receiving the pistons from them I must say I was quite impressed by the quality, quite impressive what you can get at that price! A friend here is using them on his big bore CB400 and have been racing them for 3 season, so I want to give them a try as well.
We design the valve pockets to be used with abuso valves (+2 mm vs OEM) and with my DP315 camshaft.
Using a "damaged" old piston we were able to precisely measure dome thickness and to mill the valve pockets cheking that there is enough material left in the piston dome.
Then we built a retainer system to replicate the milling precisely:
The end result:
Second component, inspired by Yoshimura double velocity stack carburettors (
http://www.bikebros.co.jp/vb/sports/sfeat/yoshimura-carburetor-en/), and more recently by what Captain has developed for his DOCH750, 3D printed double velocity stack for smoothbore CR carburettors!
First I replicated Keihin original design and I had a long stack printed to see how it comes out:
Then I took out my old books from my college class on fluid dynamics and started to design a proper double stack:
The double stack has been carefully dimensioned on my set up, so 18.5 cm intake length (from valve to the end of carb, excluding the stack), 11:1 compression ratio, 63 mm piston diameter, 31 mm carb diameter. The long stack is 8 cm long (so 1.5 cm longer than the long keihin stack), the short one just 1 cm. Based on my calculations this setup should resonate at 7800 rpm and again at 9300 rpm.
Note that the OEM profile is a truncated cone, mine are elliptical, this should prevent/reduce detachment of the airflow from the stack. Also, the edge makes a complete U turn, OEM stops at 90°, which again helps with airflow detachment.
The double stack is being 3D printed as we speak, should be ready end of next week :-)
