i have a piaggio zip 2000 model catalatyic 2t , this bike would top out at 50mph on a streight with leo vince tt pipe and 5.5g rollers this would pull very well up hills and all round really, and just recently its started to loose power will struggle to do 40mph on a streight , and really struggle to get up hills it kind of feels like its got to heavy rollers in from 30mph onwards and going up hills but it ain't , it pulls brill from 0 to 30mph but as soon as it gets past that it now take ages to even get to 40mph and will not get to 50mph with out going down a hill the rollers are very light so this ain't the case and they ust to get to 50mph with them in sooo , i dont no what i could be and it feels like it slips at about 30mph and keeps like missfiring it is a very faint missfire more like a little bogout and then pick up speed very slowly , any help would be great , and ps could it be anything to do with the contra spring ? :/ just a thought .
had same problem on my aprilia, get the clutch bell of and get some sand paper go all over the bit that touches with the clutch, also do that for clutch, it might be worth changing bell and clutch if it dosent help also check your piston rings
