6. To richen the mixture even more at 1/4 to 1/2 throttle, you could fit a mid-range needle jet with larger holes (the larger number stamped on the needle jet gives the size of the booster air holes), or to make it leaner, you could install one with smaller holes. However, because the variety of these needle jets are somewhat limited, it is more practical to change the mid-range main jet if the mixture needs correction at this throttle position.

7. The 1972 250 and 175 Pioneer & Stiletto models incorporate a slightly different carburetor main body and jet block. (Figs. 129 & 130). This jet block is an integral part of the body, therefore, the metering passages can be held to closer tolerances. This eliminates the need for a booster system, therefore these 1972 OSSA's do not use such a system.

8. The proportion of the mixture at 1/2 throttle also affects the mixture at wider throttle openings.

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