Just a few quick comments concerning the flywheel and clutches.
The current motors from Taiwan have the small balanced flywheel used on the Ambassador & NE-r, and a 2.5" pulley attached [the NE-r and Ambassador had a CVT drive]. The new flywheel is actually too small and effects the performance downward. If you use an automatic clutch it will restore the needed flywheel action [secondary flywheel action].
The WC-1 motors use an un-balanced flywheel, and removing metal normally enhances the balance.
The NE flywheel is balanced at the factory and metal can be removed without disturbing the balance.
Sadly the auto clutches currently from Taiwan are not balanced and often "shake".
It is important to understand the outcome of removing weight from the flywheel. Removing weight from the flywheel allows the motor to rev faster, and normally adds a little top end speed. There is always a loss of the flywheels ability to store energy, and mostly effects low end torque. When flywheels are lightened the throttle responds much quicker in both directions. It will not only accelerate faster , but will also slow down much quicker.
mdross1: Your brothers Whizzer sounds like the pilot jet is stopped up. Also look at the intake spacer as it often fits poorly and can leak. The symptom of a pilot jet issue is often the air mixture screw has little or no effect when adjusted. Best way to clean pilot jet [next to main jet] is with a frayed bicycle cable, never use a drill as it will enlarge the hole and make matters worse. Once carburetor is clean it will start easy, idle, and operate smoothly.
Whizzer used several different carburetors on the NE motors, most were 22 MM, however the latest are 16 MM and really take the edge off the motors power band. Several of the 22 MM versions have thin mounting flanges and often bend allowing air leaks [spray WD40 around the spacer and see if motor speeds up or slows down]. Some of them actually cracked and snapped the mounting flange from the carburetor housing. My personal motors use the 26 MM carburetor, but requires port and combustion chamber work. It is possible to reach 8,000 RPMs with the right porting, exhaust, and carburetor.
Hope this information is helpfull.
Have fun,