The rule changes for the stock CR125 engines to be used in 2010 SKUSA races were formulated to hold down initial purchase costs and maintenance costs while insuring that critical parts are available to all. How this impacts performance is of great concern to all who race these classes. Here is a how each change affects performance.
- Modifications to the stock ignition stator to adjust ignition advance are prohibited. When timing advance was set for maximum performance by slotting the stator, frequently a small amount of detonation occurred when using MS98 fuel. The reduced ignition timing advance that is forced by the rule change is designed to eliminate this detonation. This will also reduce the power the engine produces.
- Engines must use the 1999 CR125 reed cage and carb boot. The RS Honda carb boots were used by some to gain a seat positioning or power advantage. These boots are no longer available from Honda. Mandating that all use the same reed cage and boot will insure that all will have access to the same equipment. There is a power loss associated with this change.
- Any reeds that bolt onto the 1999 reed cage without modification may be used. Previously the rule allowed only stock or aftermarket direct replacement reeds be used. This new rule allows mono reeds and stiffeners. This is a reliability advantage in that the stock reeds would fail with very little running. Combinations of aftermarket reeds offer much more reliability and boost power. So this rule gains back some of the power lost by using a completely stock 1999 reed cage assembly and boot.
- Minimum squish clearance for 1997-99 cylinders is 0.050” and for 2000-2002 is 0.045”. This rule is meant as a quick check for possible non-conforming machine work on cylinders, heads and crankcases. All the no machine work rules for cylinders, heads, and crankcases are still in effect. This rule will have virtually no effect on performance.
