It's hard to understand exactly how it is getting good pressure on the friction drive but that's real cool. It doesn't look like it would be hard to add a derailleur and multisprocket to make it a multispeed friction drive... and you obviously have the skills.
The triangles create a toggle-lockup at the tire contact point. I had two springs, removed one.
Also shortened the clutch lever arm (moved cable anchor in) to increase the travel. More wheel clearance, and depreasion. Now I feel the accel, mighty micro g-force that it is.
Moved a spring inline with the clurch spring, acting as damper to the engine platform.
Two more adds, a chain idler topside, and chain guard (more to keep oil slinging away from me).
Wore the first chain out (from last fall), stretched. Gonna keep an extra in the bag too. That chain got hammered with 'experimentation'.
I don't think deraillers work at this rpm. Adding idler to dampen oscillation at low rpm now, its like a resonance, repeating. I can't see keeping enough slop to jump gears, at that speed its more controlling tension to stay on sprocket without running too tight. The idler lets me loosen the chain tension while controlling slop on idle side, engine tips into the chain tensioners under load. We'll see how these little sealed roller bearings hold up.
Considered two idlers, 'cause rolling restart shifts the tension side, but its not causing an issue, so I skipped that.
Also took dims to make a second platform for the 26cc engine, got spares, and wanna have one ready to swap when I blow the innards outta this screamer.