With the S90 if you take out the center pipe out of the header (dual walled design like some other bikes we know)
The dual pipe design allowed the chrome to not blue as easily as well as the heated tube once hot had a similar effect as pipe wrap since the hot pipe has a benefit with the exhaust extraction if I recall correctly. Pipe wrap holds in excessive heat causing the metal structure to change to be more of a crystalline structure and that weakens the pipe and causes it to age much more rapidly.
The S90s are fun bikes but you either dig deep to rebuild the stock motor for more performance with the trade-offs or you accept the shorter life of the clone motors. But, just like many other bikes, you enhance one thing and then the next weakest link becomes the problem as a result. In this case the higher speeds possible do not come with an equal positive change or increase in braking performance.
Unless you have the pieces to assemble a motor like Scott Kirn of St. Louis does with ATV125 parts and the like to create a bigger displacement motor retaining the S90 cases and gearbox which is good. But, anything more than the 104cc kit and you start looking at the need to cut the cases to fit the bigger cylinder liner. Scott does Trials competition and knows how to be the tractable lower speeds needed for that as having the experience building big displacement more hp more speed variants. He has a pretty cafe bike he built probably over 15 years ago... if you go to the Yahoo S90 groups it is on their home page.
https://groups.yahoo.com/neo/groups/Honda-S90/infoNot as elegant as some being done today but, you didn't see many 15 years ago...
Luckily the Hipsters haven't bought them up for their city wheels...
David
