Ok So i fully restored my first bike I ever had a 1974 dt175. I did body work but I had someone rebuild the motor. Let me tell you that was a challenge for the shop that did it. They kept running into problems. Especially with electrical so we just decided to convert to 12v. That fixed that even though I was trying to keep as much as possible oem. Once I got it back I found out that after it's warmed up and I have wide-open throttle sometimes when I release the throttle the reps don't go down and I either have to turn bike off and once I turn it back nannies fine or sometimes if I play with throttle and clutch I can get to bring rims back to normal. I dont know if this is related but I also have clutch slipping at times. Not through all gears and especially on the upper gears at wide open throttle. I had new pressure plates and springs put in. Does those rubber rings really have to go back in between the plates I've heard people say you don't. Also these were aftermarket plates I got on ebay could that be causing it  

Rubber rings don't strictly need to be there and some say they cause clutch slippage.  The rings are dampers and are designed in the main to stop the clutch plates from chattering around at idle with clutch pulled in.    Removing them may or may not improve your clutch, but it may be noisier.

As for the revs, you need to do the usual checks, binding cables, sticking carb slide, air leaks ect.

If they are aftermarket fibers fitted i hope they have clearance under them for the spreader rings. I guess there must be or it'd be holding plates apart & sure would slip or not drive at all. Anyway--toss them out. Must have a good freely operating cable & clearance on the arm at rest.