Yamaha YZ 250F Camshafts REMOVAL AND INSTALLATION MANUAL

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Filed Under (Yamaha) by admin on 30-12-2011

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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 hold the intake camshaft 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 cam 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. Fit the half moon shaped retainers in the grooves of the Hot Cams camshaft bearings to ensure good fit, set retainers aside for the time. Using assembly lube, lube the shim buckets, bearing surfaces for the camshafts in the cylinder head, and pack some in the camshaft bearings. Set the exhaust cam into the cylinder head casting while at the same time fitting the cam chain over the sprocket. Make sure that you keep all the cam chain slack to the back of the engine. The cam chain pulls the camshaft sprockets in a counter clockwise direction and the slack of the chain must be kept on the cam chain tensioner side of the engine. The exhaust cam has two timing marks on it. When correctly installed one mark will be at the 9 o’clock position and the other mark will be at the 12 o’clock position. When correctly timed the mark at 9 o’clock will be aligned with the valve cover gasket surface. Repeat the above process for the intake camshaft. Again, make sure you keep the chain slack to the cam chain tensioner side of the engine. Check to be sure the crankshaft is still at TDC. The intake cam has two timing marks also. One at 12 o’clock and the other at 3 o’clock. When both cams are installed correctly, the valve cover gasket surface will form a straight line through the exhaust timing mark at 9 o’clock and the intake timing mark at 3 o’clock

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