2006 Arctic Cat Y-6/Y-12 50cc and 90cc Service Manual, Page 51Get this manual
38Inspect the transmission bearings and oil sealsReplace any worn or broken seals with new onesReplace any rough or worn bearings; then install the gasket and two alignment pins and press the drive gear into the bearing39Install the final drive gear, intermediate gear, and the final driven gear shaft into the left-side crankcase DSC02296
34Rotate the flywheel to align the "T" mark to the timing line on the right-side crankcase coverNOTE: Rotate the flywheel clockwise several revolutions to purge oil from camshaft lobes, tappets, and drive chain
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35Using thickness gauge, adjust the tappet clearance to specifications; then holding the adjuster stationary, tighten the valve adjuster jam nuts securelyRecheck the adjustment with the thickness gauge36Install the spark plug and tighten to specifications37Install the cylinder head cover and secure with four cap screwsTighten to specifications