Well I finall got the new Reliable servo motor. It installed pretty easily. I had to get a new belt as the old one was too short. The new one is 3 3/4 inches longer for the record. My new motor has the 90mm pulley. It is a very complete kit, I didn't have to get anything extra except a belt.
I haven't really had time to explore it completely but so far it works pretty well. The "ratio arm" for lack of a better term is a bit short so I will either make a bit longer arm or mount the link closer to the treadle center to make it less sensitive. I did try various speeds. I'm on 15 right at the moment. The instructions are a bit vague so I just tried vaious ones. It sews about 1 stich per sec then jumps to probably 5 then goes up pretty fast from there. If you move the arm slowly by hand you can get progressive speed but it is very sensitive. You need a steady foot and some patience but it is far better than the clutch motor. The bottom line is I just need to practice more I think. Maybe I'll just bowwow a bit of technology from the race car and make a "throttle stop".. haha
I'm not sure what the 50mm pulley will do. I think the initial speed will be slower to the point of being too slow and the "jump" speed will still be not linear enough but better.
Somewhere there was a thread about a convesrion or modification to the servo switch to make it smoother and more linear but i haven't been able to find it.
It has plenty of power even going very slow.
I have one other question that maybe should be in a separate thread but here it is: There is a pin on the tensioner that apparently wears a little and make the tension adjustment very sensitive. I tried to buy one of these at a local sewing machine repair store and they didn't know what I needed at all. I've tried to find it as a part number but again can't find it.
Can anyone help??