After so many years and hundreds of new and used scooters and motorcycles coming into the shop plus the consumers who call the following is quite clear.
Fuel and Air play a huge part in the performance of the 50cc scooters and of course all scooters and motorcycle due to the golden rule of air fuel and spark and away you go. At Scootpower’s very Scootertronics jets play a huge role in getting the scooters with the correct amount of mixture and velocity.
Keep this ratio of fuel and air on the rich side the air cooled scooter and motorcycle runs better that running lean which a vast majority of scooters are running lean once they leave factory for the US EPA which has all this crazy EGR hoses and catch cans all over the place. On scooters I remove all EGR and raise the main jet to 90/95 and pilot to a 45 (50cc stock is 35) 150 to 115 45 on a air cooled four stroke 50cc or 150cc scooter, two stroke 50cc) models to pilot also 45 the main jet consumers can choose 80-120 according to their engine (two Stroke) whether they have an upgrade to exhaust and cylinder or one without the other, a stock Zuma should get a 80 please check yours first with most finding a 75 main. When cylinders and exhaust are upgraded air filters and jets go up for two stroke to around 97 seems to do well in the 17.5 – 19mm carbs above 19mm (21mm) use larger ones due to a high powered pipe and cylinder that has better ports and more ports than a stock iron or a generic iron 70cc kit. Scootertronics carries most sizes that consumers need the most with the round and hex for PWK and a few other CVK carbs. All jets are Keihin for CVK carbs found in Kymco four stroke and GY6 four stroke. Mikuni jets are featured along with Dellorto jets for all two stroke which include the round jets used in Minerlli engine carbs. PWK and Flatslide use keihin jets with using both round and hex sizes. Air filters play a huge roll with jetting. The GY6 50 an UNI Dual Layer is best for stock and slight mods at 70cc with exhaust. The get the most power from a GY6 50cc 139QMB engine is using a “cold air intake” which is really longer tube and open flow air filter that creates the correct velocity of air when added to the fuel delivered to the engine through a