In the AFM, where we primarily race, the classes that the NC were legal for (at the time we started this project) were 450 Superbike and Formula-One. 450 Superbike’s rules were fairly simple and open. We were allowed to run any street-based motorcycle with a displacement equal to 450cc +1mm of bore over that. In most cases, this allows for an engine in the mid-460cc range. Formula-One was simply out of the question as we would be running against GSX-R750s and other 140hp+ motorcycles. This was just not our idea of fun.
However, Lohmeyer also liked to race in other organizations that had more mid-sized classes to compete in. These classes allowed bikes up to the size of the SV-650 to compete, thus, the SV became the bike we needed to beat. Based on our rules and our needs, I set out to work with the numbers. I looked at the space we were working with and figured we were stuck with a maximum bore size of 58mm (+3mm over stock). This was even considered too large using the stock cast-in liners as we saw evidence of the liner breaking through on the last 58mm motor we looked at. In addition, as I was trying to find a piston that would work for us, I found a shortage of high-quality piston rings to choose from at that size. The best ring I was able to come up with was a 57mm ring from the Yamaha FZR400. So, this is how I derived at the bore size of 57mm.
Now that we had our basic engine configuration, we needed to find the right people to do the job for us. This is probably one of the most difficult tasks in the racing industry. Everyone “says” they can do what you need. However, who can really do it the best, and on time? Those are the biggest hurdles we continue to face to this day.Based on that bore size, I calculated a stroke that would get us the desired displacement we were looking for. Although the AFM rules allow 450cc +1mm, some of the classes that Lohmeyer was anticipating racing in didn’t allow over 450cc. So, we were shooting for the closest thing to 450cc. With a 2mm increase in bore and a 2.5mm increase in stroke, we ended up with 454cc. This was what we ended up going with. As we found out later, any further stroking would have spelled eminent death for this motor, as the crankshaft was already at the ragged edge of strength.