Ive been trying to fit in some time working on the GPX in between packing (poss moving soon, tho staying local) & working and Ive noticed a knocking from the crank case area at low revs (upto 2750/3000 rpm) then it disappears & all sounds smooth. The bike has a very rough tick over, when it ticks over at all! The carbs sound as if they need balancing to me also! Any (polite!) surgestions would be greatfully received!