enable transmission of power thereby performing a speed reduction at the second gear position or the third gear position lubricating oil supply holes 69 and 70 leading to the needle bearings 63 and 64 for bearing the second gear position driven gear 61 and the third gear position driven gear 62 are also formed in the counter shaft 9 the rear portion counter shaft 9 b is provided with a forward running driving gear 71 and a backward running driving gear 72 these are both floating gears of which the one engaged with a manual dog clutch 73 provided at an intermediate position therebetween is fixed to a shaft whereby transmission of power is enabled lubricating oil supply holes 76 and 77 for supplying a lubricating oil to needle bearings 74 and 75 respectively bearing the forward running driving gear 71 and the backward running driving gear 72 are formed in the rear portion counter shaft 9 b the counter shaft 9 includes the front portion counter shaft 9 a and the rear portion counter shaft 9 b integrated with each other and provided with a center hole which is partitioned into a front portion center hole 79 and a rear portion center hole 80 by a steel ball 78 press fitted in a narrowest portion thereof the supply of a working oil to the second and third gear position oil hydraulic type multiple disk clutches 65 and 66 is conducted from the side of the front crankcase cover 24 through a double wall pipe 81 the double wall pipe 81 includes an outer pipe 81 a and an inner pipe 81 b the working oil for the second gear.