I have a 2003 Kinetic I got new 1.2 years ago. It was not running to badly until I had to replace the rear rim with a new do to lose of many spokes in a short time. I have cleaned carb well. It has a #30 pilot jet & a #48 main jet. It has 4755 miles. I am running 40:1 fuel. Fuel filter has been replaced and the banjo screen is clean. The spark is good also. There is good spark and fuel flow to the bowl. The float is in good shape and freely moving. The carb was a little lose on the intake tube but that is taken care of.
The original problem was that it did not get top speed it dropped 8 MPH off top (30-34 MPH). Then it drop 7 more. Then drop to 12.5 MPH and finally 8 MPH. During this drop it stopped also climbing hills. I have a lot of hills around here. some times it would only go up them at 10 MPH with help pedaling, but that is better than pushing for the 1/2 mile to 1 mile hill. I was able to get it back to 20 MPH top speed but only after free running it with 10 PSI air into air intake. It now will almost not start and only run at sort of idle with full/partial throttle. I have tried adjusting the low speed idle screw ( no damage) and does not matter where it is set. I have also tried the mixture screw (no damage) and still changes. It will run with both screws closed down.