Performance Tuning a Suzuki
Q-How fast should my Suzuki go?
- A-Stock the FA50 should reach 28-30mph. Stock the FZ50 should reach 30-34mph A correctly adjusted carburetor and Muffler cleaning are the two most important factors in reaching the stock speeds.
Q-Why won't my Suzuki start or idle well?
- A-Common problems are idle speed and mixture adjustments, clogged idle jet, and rusted fuel bowl floats.
Q-How do I make my Suzuki faster?
- A-It's important to start with a bike that at reaches the stock speeds. If you can't reach near these speeds something is wrong and all future adjustments will be off. Tuning a FA50 to hit 28 mph is cheaper, easier than tuning to break 32 mph. Start with Fred's Guide.
Increasing power, and top end performance.
One of the fastest and virtually free improvements is increasing compression by milling or shaving down the head. Raising compression boosts power across all ranges. The original motors had low 6.5:1 compression. It's possible to remove at least 2 millimeters from the head, bringing the mating surface even with the cooling fins, and remove the head gasket while still using 87 octane without issue. At least 2mm more can be removed, compare head gasket diameter to combustion chamber diameter for a gauge of piston clearances.
The stock air filter is restrictive. It is possible to drill a few holes to increase airflow. Other easy options for the FA50 include removing the plastic airbox and reusing the rubber elbow connecting it to the carb. Various "performance" auto parts store valve cover breathers will fit this elbow. The FZ50 air filter bolts on to the carb with 2 screws. New filter housing can be either screwed to bracket or a rubber hose can be fitted to the carb throat to adapt other filters.
One of the few performance parts available for the 49cc Suzuki motor was the Simonini Expansion chamber. Powerband is a little high, it kicks in at about 22mph. There is some loss of low end power but worth the major increase in top end power. Expect to increase your carburetor jetting to prevent a lean condition and to maximize top end power. The lost low end can be regained by increasing the compression if not already done.
FA50 tire size is restricted by the minimal clearance to the rear mounted carburetor. Low tire pressure can add significant drag, up to a 5 mph loss. Inflate to 35 psi or higher for less resistance. FZ50 rear tire size can be increased from a 12x3" tire to 12x4" with minimal changes. This adds about 2" in tire height which will increase gearing and top end. A 12x3.5" tire should fit with out any changes. The 12x4" requires filing a bump off the transmission and off setting the 2 wheel pieces by 1/4" with washers.
The FA50 service manual recommends running 500ml 20w-40 multi-weight oil. Changing to Mobil 1 0w-30 synthetic is worth a 2-4mph increase. Another common problem is an overfilled transmission. More than 500ml will add excessive drag on the drivetrain. Its only necessary to fill the transmission 300ml.
The FZ50 has a 2 speed automatic transmission. The 2nd speed clutch works by centrifugal force dictated by rpm. Typically they shift between 10-12 mph.