Thought i'd have a look at the Readspeed 5-plate 'supergrip' clutch kit, the red plates look good, 1.2mm steels are fine, and springs looked very similar to MB ones. So i did my usual test......i popped them into a vice so i could measure their length when fully compressed. On the outset the MB spring is 36mm and the RS is 35mm, so very little in it. They both compress to roughly 13.7mm, but when taken out of the vice.....only the MB one returns to its original length. The RS one is now 4.5mm shorter!
I don't have equipment to test the pressure needed to compress MB vs RS, but when done unscientifically by hand the RS feels like it needs more pressure, which whilst being heavier on the lever will result in less clutch slip. I carried on with this and pre-compressed a full set of RS springs in the vice, so they are all the same length now......i'll carry on with the clutch build and build one with MB springs and RS red plates, and the other with RS springs and RS plates......so 2 clutches, same plates, different springs.....and will see how they both feel and perform.
MB spring on the left @ 36mm, Readspeed pair of springs on right @ 35mm:

Untitled by Scooterotica Scooter Garage, on Flickr
Both in the vice uncompressed:

Untitled by Scooterotica Scooter Garage, on Flickr
Both in the vice, compressed to 13.7mm:

Untitled by Scooterotica Scooter Garage, on Flickr
MB back to 36mm on the left, compressed RS spring in middle @ 30.5mm, and uncompressed RS spring on right to compare (still @ 35mm):

Untitled by Scooterotica Scooter Garage, on Flickr
Just an observation at this point, its the grip of the clutch plates and the correct free play which concerns me mostly, followed by pressure and coil-bound length of spring. The lack of return to form on the RS is just an observation at this point, and may or may not be a problem, i'll soon find out.
