O.K. I do not want to be a spoilsport or smart aleck or whatever you want to call me. But getting to and over 15k in rpm with a CBX motor is going to be a challenge. Making the valves out of titanium will not by itself keep them from floating. The springs are the weak link here. I cannot see any spring design packaged in the given space that will get a CBX motor to 18,000 rpm
Overall, the CBX engine is a pretty heavy sister. Pointing towards the crank is something anybody with a little understanding of internal combustion mechanics would do for these kind of rpms.
Making the pistons lighter together with the rods was obviously addressed and looks good.
The stock CBX motor is 64.5 x 53.4 mm bore x stroke, which by definition is "oversquare". As the most common and easiest changes to the bore x stroke relationship is an increased bore, the engine becomes even more oversquare.
This is good for the ability to run at higher rpms, but it decreases the capability to incorporate higher compression ratios. Achieving optimum "breathing" is another challenge for oversquare motors. That limits the horsepower you will get out of it.
Finally, this is what it all boils down to:
If you're willing to inspect it after every race and replace as necessary, maybe it can work.
