Hi Mark
happy to know that you will keep your great 500 project
concerning sprocket/pivot distance, I think that have been spent thousands words but only few people can appreciate advantages or issues
to be honest distance is only one paramenter to obtain a good frame, relative height between two points, center of gravity,
setting of rear shock and others can affect bike handling and motricity.
as i told, in my project i tryed to move forward pivot and put longer swingarm, so I tryed to replicate relative
position of critical points directly from a GP chassis but, at least, bigger and heavier engine change thinghs
all whole bikes result heavier than last two stroke factory machines, COG fall in different position and horsepower are far less.
in practice, when i met Mark and his bike on track, he was always faster than me and bikes seems to run well, also in a short racetrack.
so, what is the real sense of our project ?
first of all, try to build something with our knowledge, try do do our best with material, donor parts and tools we have
second, have fun and satisfaction ride our creation
third try to obtain a decent tune (not easy with wide range of modification done)
I stop here !
if somone else have better ride skills and want to test bikes and themselves in a race, well !
probably also in this situation, for common rider, a good build special bike works fine
f you want more, and your skill ability are very good, you need more tuning, and more and more, in that case, probably, you can find the limits of an home made bike. some could be fixed with better components, some other not, probably you need to redesign entire bike.
I'm so far from this situation but, remember, that our projects start form a 30 year old bike and, defintely we got an improvement from the originals.