Regardless of how my current Malossi spring stands up to a longer run, l have designed a revised spring set up for in my quest for FS spring compliance over power! Although l may not actually fit this one until after my XBs pending MOT.
One annoying aspect of looking for springs online is that there are many sellers of stronger racing clutch springs for various bikes, but few specify actual dimensions!
I still have to visit a bike breakers with my electronic micrometer to measure a few with.
There is a 2mm gap above the spring and the FS frame. This is why l estimate that an 18mm OD spring is possible. Towards the front of the FS the frame curves down towards the spring socket, which presents a snag, but also a potential solution. By grinding off the end of a larger springs tapered end coil you can create a natural recess which the curved FS frame will slot into.
My plan for a larger spring was always to get an end stop with a 15mm stub one side and a 12 or 13mm stub opposite turned on a lathe which will clip into the FS spring socket and retain a larger spring without having to modify the FS.
Not having obtained an 18mm spring yet, l hit on the idea of using one of my Honda 125 valve springs as a ‘test mule’. These springs are 27mm long by 20mm OD. Too wide, but possible by grinding a flat on one side of the spring so that it will fit in the FS. Then l thought about using this as well as the Malossi by resting it piggy back on the smaller spring. I have a 20mm stop washer to hold both springs at the adjuster end. At the front end l ground off the end of the Honda springs last coil so that it slots in above the Malossi due to it’s shorter effective length. This dual spring combo is significantly more powerful than the previous single, but strangely more easily compressible than any of my Indiamart colour springs. I can’t wait to try this out, but there’s no time to install it before my next ride out.