Yamaha YZ400/426F Camshafts REMOVAL AND INSTALLATION MANUAL

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Filed Under (Yamaha) by admin on 01-01-2012

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Cleanliness is always a good place to start. Make sure the motorcycle is cleaned thoroughly before you start. It would be advisable to use an engine degreaser on the frame and the engine. This will ensure a clean engine during the assembly process and less of a chance of thread damage and/or dirt contamination in the engine during reassembly. And as always, replace any fiber-based gasket that was moved in any way, i.e.: cam chain tensioner. You will need basic hand tools and a torque wrench, machine towels (rags), some cleaning solvent, and a cam chain tensioner gasket. And the Hot Cams’ Degree Wheel Kit if you so desire. We will start by removing the tank and seat, top engine mount, and the cam cover. Remove the crankshaft cap and timing hole cap on the left engine case cover. Remove the spark plug. Rotate the engine in a counter clockwise (CCW) direction. Position the engine on top dead center (TDC) using the mark on the flywheel or better yet a degree wheel using a positive stop. Be sure to notice that the intake valves were the last to move, this will ensure the engine of being on “true” TDC. True top dead center occurs when both the intake and exhaust valve are closed when the piston is at TDC. This is technically the end of the compression stroke and the Page 1
beginning of the power stroke. The “artificial” TDC is during the overlap when both the intake and exhaust valves would be open. Note the positioning of the cam lobes (their included angle will be close to 170 degrees), this will help during the installation of your new Hot Cams camshafts Remove the cap bolt on the end of the cam chain tensioner block, be aware of the copper washer. Release the spring tension on the cam chain tensioner by turning the flat blade screw slot inside the adjuster block in a clockwise (CW) direction; it will lock in the retracted position. Remove the two 8mm headed bolts that hold the cam chain tensioner to the cylinder block. Remove and discard the gasket. Remove the 4 bolts that hold the exhaust cam cap in place, lift the cam cap off. It may be necessary to pry very lightly on the cap to lift it off its dowel pins. Do not use the cam lobes as the pry point. Be careful not to drop the dowels and also be careful to not lose the half moon shaped retainer for the bearing under the cam cap. Remove the 6 bolts that secure the intake cam cap and lift the cam cap off the camshaft, again, be careful to not drop the retainer or dowels. Lift the intake camshaft out of its pocket in the cylinder head casting. Remove the cam chain from the sprocket, set the stock camshaft aside. Lift the exhaust camshaft out of its pocket in the cylinder head casting and remove the chain from the sprocket. Do not drop the cam chain, dangle it over the side of the engine while keeping slight upward pressure on the chain to maintain its position on the drive sprocket on the crankshaft

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