I have got a piaggio zip 2t ac with malossi 70, 21mm universal carb with a 102 jet, stage 6 open air filter, yasuni exhaust, would anyone know the perfect idel screw and mixture screw placements, like how many turns, because it's bogging when riding, starts bogging on 1/4 throttle, I have heard this can be caused by wrong jetting, idel and mixture screws wrong set up, roller weights, air leaks. Could someone help with this??
First off, put the standard 17mm carb back on and the standard airbox. Put the air/fuel mix screw at 2 turns out and the slide needle on the middle slot. Jet that carb to the Yasuni exhaust. Then play with the roller weights to get to the place you are happy with on the takeoff/acceleration/pull. Now you can play with having the open filter on it. With the open filter you will need to re-jet UP the carb, by about 10 - 15%, to compensate for the added airflow created by the open air filter. When you have this jetting right, the bike will take off like a scalded cat. NOTE: Jetting isn't a case of "what size jet should I put in". There is no jet size that fits all, every bike is different, even the same ones. You need to buy the packs of 10 and start at the biggest and work downwards until you get that crisp pick up and constant acceleration. Don't be surprised if you end up with a jet in the 80's somewhere. Keep an eye on the colour of the spark plug. It should be a nice ginger colour if it's fuelling properly. Too white looking and it's too lean, (up one jet size), too black and it's too rich, (down one jet size). LEAN = RUNS HOT AND KILLS THE MOTOR When you've mastered the art of jetting the carb and balancing the roller weights, then you can move on to changing the carb sizes and doing the whole thing all over again to suit your desired carburetter. NOTE #2: Dump the 21mm carb, it's too big for that set-up. The only thing it will do is cost you more to keep the fuel flowing. NOTE#3: You may also have to fit a gear-up kit to bring the upper revs back down a bit so it doesn't over-rev the engine at full bore.
