In R51/2, the dynamo is placed on the upper part of the crankcase.
But in R51/3, the ignition coil and the dynamo having large heating value are placed together on the forward of the crankcase and it has adopted the mechanism to cool them.
It feed the air of the rear air cleaner case to the combustion chambers of the left and right, also to the dynamo chamber in front of the crankcase, using the respiration of switching the port valve.
In this way, it has taken the balance of the left and right of the inlet pressure and cooling.
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