Mercury F4TZ-6256-B Sprocket - Camshaft

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To check camshaft end play, must first remove the timing chain cover and the rocker arm shafts. Rotate the camshaft as far back in its bore as possible or as far forward as possible and then install a dial indicator so that its index is on sprocket bolt with the indicator moved to zero. You can now pry the camshaft forward using a large screwdriver or pry bar between the camshaft sprocket and the block; then, compare a dial indicator reading taken at the beginning and at the end of this operation to the amount of end play recommend and if the end play exceed the camshaft thrust plate should be replace. For timing chain and tensioner inspection, too, ease off the timing chain cover and timing chain tensioner, noting a reference mark on the block. Twist the crankshaft anti-clockwise until the right side of the chain is tight then measure from the reference point to the right side. If the deflection is still present, turn the crankshaft clockwise to take up any lateral movement on the left side and recheck; the amount of either will depend on how much it changed to determine the degree of slack in the timing chain and, if severe enough, it should be replaced. It is the component that should be checked for any signs of wear or damage and if so should be changed; this part should be retracted before it is engaged. To remove the chain and sprocket you will have to drain off the cooling system and the engine oil, then remove the oil pan, the drive belt and finally remove the timing chain cover. Synchronize the timing marks by rotating the crankshaft, note/unscrew or remove the timing chain tensioner or camshaft sprocket bolt and/ or take off the sprockets and the chain but do not facilitate the crankshaft or the camshaft. If required then it is possible to take out chain guide bolts and then turn out the guide. For refitting, align the crankshaft and the camshaft sprocket timing marks, fit the crankshaft pulley if removed and tighten the guide bolts on the chain if removed. Position the sprockets in such a manner that their timing marks face each other, then fit them onto the crankshaft and the camshaft in order; confirm that the chain is central and not loose.Apply an additional 15-35 m/kg or ft/lb on the camshaft sprocket bolt, then compress the tensioner pad with the help of a sharp-tipped probe tool in order to pull back the tensioner into the required position.Last is to fit the timing chain tensioner and fasten it's nuts and bolts, after reinstalling other parts in reverse order start the engine and look for leakage of oil or coolant.

Push the camshaft all the way to the rear of its travel in the block, install a dial indicator so the indicator stem is on the camshaft gear/sprocket retaining bolt, and zero the dial indicator in this position. Then, using a large screwdriver between the camshaft gear/sprocket and the block, pull the camshaft forward and release it. The reading on the dial indicator will give you the endplay measurement.

Turn the crankshaft in a counterclockwise direction (viewed from the front of the engine) to take up the slack on the left side of the chain.

Drape the chain over the camshaft sprocket, turn the sprocket until the timing mark faces down (6 o'clock position), and mesh the chain with the crankshaft sprocket.

Rotate the engine 360-degrees CLOCKWISE, remove the rocker arms from the remaining cylinders using the special valve spring compressing tool, and rotate the engine 360 degrees CLOCKWISE back to the TDC number 1 position.

Ensure that a straight line passes through the center of the camshaft, the camshaft timing mark (in the 6 o'clock position), the crankshaft timing mark (in the 12 o'clock position), and the center of the crankshaft.

Remove the top cassette bolt and the camshaft sprocket, then remove the lower cassette-to-block bolt. Remove the cassette, chain, and jack shaft sprocket.