If you take the belt off you can see that the rear pulleys do not touch ....there is room there for a noticable gain ...the inside of those pulleys can be machined down with out a loss of strength so they pinch more and then you can machine the front pulley down in where the belt sits at low speed to make it sit lower in the "V" don't machine into the higher part or this will effect top end.. this will make that bike rip out the hole...back too OG prob ..I think you stretched the belt cuz that variator dremel job does not affect belt tension those belts are hard to come by and yes you should always take variator off to change those belts and they cant be gettin oily ...If you could find a 6 roller variator and put that on there with only 3 rollers and then do the machining ...also that stock pyramid cylinder can really fly... get a metra puch 65cc piston and have that thing bored out and a port job...love them derbeeez...oh that belt is rumored to be the same belt as some bakery machine(for reals)...hahaha serious though...If you cant find one I could dig one up as I already promised a lady with a derbi one ..better see how many I got ...good luck