Those who have been on the forum for a while may be aware I've been tinkering with the suspension on my 750 for quite some time. Chasing a problem with ride and handling that just seemed impossible to identify. Two sets of top line rear shocks, endless front spring rate changes, endless adjustments to the cartridge emulators in the front forks...... on and on it went, never really being 'right'. Problem always felt like it was in the back suspension. Harsh ride, front tending to 'pogo' at slow speed over undulating roads
Well I've finally identified it, and thought it worth sharing. Front rebound compression damping was never slow enough. Now that it has been slowed down to about the same as in this video the bike rides and handles like a dream. I used the video as my guide to set rebound damping speed (and I guarantee the typical damper rod fork bike will be NOTHING like as controlled return of the R6). That's how slow and controlled it has to be.
[youtube]https://www.youtube.com/watch?v=mJV-jhEtjz4[/youtube]
Obviously as the Zephyrs have no 'external adjusters' to achieve that compression rebound return speed I'm using 15W oil, with one of the two rebound damping holes in the damper rod reduced in size by about 50%. And this is with fairly new fork outer tubes (worn tubes will require a much heavier oil). But you can't just dump in 15 or 20+ weight oil. That will cause major problems in the compression damping side. The forks will just lock up on a bit hit because such heavy oil can't be forced through the compression bleed holes. That problem has to be addressed also, which is relatively easily done with cartridge emulators. If you get the rebound damping side correct the compression damping seems to be not that critical, so can be left on the softer side for a nice compliant straight line ride, yet with correct rate springs still handles very well in the corners.
For what its worth, I weigh roughly 95Kg in gear and have found a 0.90Kg spring in one leg, and a 0.85kg in the other to be a good compromise between performance and ride quality.
My experience is that the bike will never handle and ride anywhere near as good as it can unless front rebound damping speed is addressed. A stock damper rod with old 10W fork oil, and a few k's under its belt , and I doubt the 750 will have ANY front rebound damping