I stick with the 3D clutch. I have tried different 4D clutches. There was one Kyosho 4D with a large flywheel. The flywheel was too heavy. The normal 4D feels about like the Mugen 4D. I tried leaving out 2 of the 4 weights, but I could not make the clutch fully engage like I wanted. (Too smooth, and melted the clutch pad) With 4 weights, I had to really tighten down the spring a lot. This provided a heavy hit, but needs a really hard spring. I like the 3D, or 4D with the flyweights lightened. I also like the Orion square clutch spring in all of them. I have tried the RRR lightweight clutch on the Evolva with success. Use the entire RRR clutch, with the Evolva clutchbell, and gears. It just requires some chassis machining to get the starter wheel in there. There again I used the 3D with lightened flyweights, and it is really nice. I also start out showing about 1.3mm of clutch nut threads with the Orion spring.
