I couldn't remember whom had asked the question on the Clutch discs for the 90cc vs 70cc...
Took a little digging...plus I had to be on the computer instead of the tablet to do this post.
"S90 clutches 101
The auto clutch disks from the CT90 will definitely not work.
I'm not sure about the CL70 or the S65 but I can offer the following.
The early S90 uses the same clutch as the pushrod 87cc CA200. They both have 2 fiber discs.
The C110 (50cc pushrod sport model with the manual clutch) has a thicker single fiber clutch plate that fits in the CA200 and S90.
(this I'm told was done in the 60's for added clutch pressure when higher performance motors were built)
Because it is thicker when 2 are used in a CA200 or S90 it requires a shim under the clutch actuator (against the actuator bearing).
Keep in mind thicker clutch plates compress the clutch springs more and cause the clutch housing to move closer to the center of the engine, NOT closer to the actuator. If thicker clutch plates are used a shim over the actuator bearing roughly equal to the added plate thickness is required. This can be done with a common (5/16" washer) if memory serves me correctly.
I would expect that this is also true for later S90 clutches as the main difference is that they have a larger root diameter in the crankshaft splines and use the same clutch plates as the early models. (someone correct me on this if I'm mistaken)
ScottK
St. Louis"
Scott is a member of the Yahoo S90 group
David
I have a bag full of clutch friction discs. Probably 25 or 30 of them.
None of them are the exact part number for the S90.
There are some S65, CL90, ATC, etc. I don't see any reason why they wouldn't work. The grooves are slightly different on some of them. But they fit the clutch basket and the thickness seems the same.
Can I use them in my 1965 S90?