ive got a piaggio nrg and trying to setup a engine that ive rebilt with malossi 70s and yasuni c16 exhaust 21mm carb but bogs on pull away when its hot about 70c fine when it kicks in and its fine when the engines cold pulls of line nicely but soon as it gets a tad hot its poo pulling away no power at all till hits power band? ino transmissions setup right rollers got adjustable clutch springs so must b jetting but the higher jet i go the worse it is pulling away when hot? any ideas ?
Your fuel mixture is too rich and the plug will probably be black with soot. You may have over-jetted the carb too much with the main jet size. Try adjusting the jet needle height by putting the needle circlip into a higher groove of the needle, thus lowering it and weakening the mid-range mixture, which is where I think your problem lies. If the top groove of the needle doesn't sort the problem out, jet down one size, move the needle circlip to the middle groove and try again. Rinse and repeat until the bike will suddenly get a lot livelier as the mid-rrange mixture dials in correctly.
ok thanks i will give that a go i have tryed lowering the clip on needle but not hiring it so you could be right. i thought about pilot jets can that change the lower range on the throttle ?
the idle jet only covers the idling mixture. Leave the idle jet and idle running screws alone, if the bike idles OK. At anything over idle speed, the needle takes over from the idle jet and sets the mid-range mixture via the height and the tapered section of the needle. You can get needles with different tapers, but for now work with the one you have and get the mixture right before changing anything else.
