Puffs wrote:Yes, metal might be better.
The R6 has a hard, short-stroke racing suspension, so if an R6 shock feels soft on your 660 it means the 660 has another transmission ratio (more movement rear wheel per movement shock). Is the shock's stroke compatible with the 660's suspension construction? And also, if you fit a stiffer spring on the same shock, you may find it is underdamped.
I don't know details of the original spring on the 660, but you can estimate the spring rate using:
Spring rate formula.jpg
Or search for 'spring rate calculator' on the web.
Interestingly it seems that the R6 actually has about the same stroke as the MZ shock. It does seem as though the linkage is slightly different, which is accounting for the difference in spring rate observed.
I actually used that formula yesterday and estimated a spring rate of 145-155 N/mm on the stock spring (depending on the alloy of steel being used, which is an unknown). This is in line with the aftermarket shock I saw on the internet being advertised as 175 N/mm. It seems that the stock spring is just about perfect for my weight. In talking with a suspension guy it seems that because of the slightly less overall length of the R6 shock it would behoove me to shorten the dogbones slightly in order to get the same ride height as stock. I am going to play around with making some dogbones that are slightly shorter.
Re: the under-dampened: I fully expect it to be. My goal was to find a nice-ish inexpensive OEM shock for cheap that is rebuild-able, make the spring work, then play around with the shim stacks inside and get it optimized for my riding. Seems that it will be a little cheaper than just buying a custom shock, AND I get to learn about valving and shock internals and suspension in general. Every little project I do I like to learn something. The R6 shock from those years really fit the bill: very close to the same size, very cheap (I got this one for 60 bucks), and a nice shock (triple clicker adjustments).