Cam Chain Adjustment
Posted: Sat Sep 19, 2015 3:32 pm
If you set the cam chain tension as per manual, just by undoing the 10 mm chrome dome nut on the back of the cylinder barrels, and re-tightening it, if the tensioner itself is sticky (not at all uncommon), it may not have done very much adjustment at all and the chain could still be quite loose, hence you may still have mysterious internal rumblings.
I find it best to set the cam chain tension with the cam cover off and follow this process. A second pair of hands holding a torch (or wearing a head torch) helps. [That's flashlight, or similar,for you blokes north of the dividing line. (ed)]
Remove both cam cover and RH crank end cap.
Take a 17 mm ring spanner and slowly rotate engine forward (clockwise) while looking down the front run of the long A chain that runs from crankshaft to exhaust cam. You will see the run of the chain pulled very tight as the crank 'pulls' down on the load of turning the camshafts. All the slack in the chain will be moved to the rear run of the chain.
Now turn the motor backwards slightly and you will see all the slack now move to the front run of the chain. (Doing this just to share the principle of removing slack).
OK, now loosen off the 10 mm chrome dome nut on back of barrels a few turns (don't take it all the way off).
Now put as much forward rotational pressure on the 17 mm spanner as necessary to move all the load onto the front of the cam chain. Just enough for the crank to be pulling down on the chain, but not enough to actually rotate the crankshaft.
While holding that forward rotational pressure, on the end of the crankshaft, now push down very firmly with your thumb on the rounded very top part of the 'A' tensioner, so that it bows down and in towards the crankshaft and takes up all the slack in the back of the chain. While pushing down on the top of the tensioner, now tighten the lock nut so that it is just firmly nipped up - ie; not too tight.
Now when you slowly rotate the engine backwards just a little, you should have much less slack in the chain.
For the shorter B chain, undo the lock nut and pinch bolt on the front of the cylinder head. Now push down firmly on the bottom run of the chain and then release the downwards pressure. The tensioner should bounce up and down freely and you will observe the rod on the front end of the tensioner sliding in and out of the hole in the cylinder head.
By slightly rotating the crankshaft back and forth, you will see the slack in the chain move from the top to the bottom runs of the chain.
So, once again, holding that forward rotational pressure on the end of the crankshaft, the tensioner should automatically spring up to take all the slack out of the bottom run of the short 'B' chain. While holding that forward rotational pressure on the crankshaft, just nip up the pinch bolt on the front of the cylinder head, then do up the lock nut. They just need to be nipped up firm. Not too tight at all.
If, after doing this, you still have noises coming from the middle of the rocker cover, you may be up for a set of oversize Oldham coupling joints to join the pairs of cam shafts
I find it best to set the cam chain tension with the cam cover off and follow this process. A second pair of hands holding a torch (or wearing a head torch) helps. [That's flashlight, or similar,for you blokes north of the dividing line. (ed)]
Remove both cam cover and RH crank end cap.
Take a 17 mm ring spanner and slowly rotate engine forward (clockwise) while looking down the front run of the long A chain that runs from crankshaft to exhaust cam. You will see the run of the chain pulled very tight as the crank 'pulls' down on the load of turning the camshafts. All the slack in the chain will be moved to the rear run of the chain.
Now turn the motor backwards slightly and you will see all the slack now move to the front run of the chain. (Doing this just to share the principle of removing slack).
OK, now loosen off the 10 mm chrome dome nut on back of barrels a few turns (don't take it all the way off).
Now put as much forward rotational pressure on the 17 mm spanner as necessary to move all the load onto the front of the cam chain. Just enough for the crank to be pulling down on the chain, but not enough to actually rotate the crankshaft.
While holding that forward rotational pressure, on the end of the crankshaft, now push down very firmly with your thumb on the rounded very top part of the 'A' tensioner, so that it bows down and in towards the crankshaft and takes up all the slack in the back of the chain. While pushing down on the top of the tensioner, now tighten the lock nut so that it is just firmly nipped up - ie; not too tight.
Now when you slowly rotate the engine backwards just a little, you should have much less slack in the chain.
For the shorter B chain, undo the lock nut and pinch bolt on the front of the cylinder head. Now push down firmly on the bottom run of the chain and then release the downwards pressure. The tensioner should bounce up and down freely and you will observe the rod on the front end of the tensioner sliding in and out of the hole in the cylinder head.
By slightly rotating the crankshaft back and forth, you will see the slack in the chain move from the top to the bottom runs of the chain.
So, once again, holding that forward rotational pressure on the end of the crankshaft, the tensioner should automatically spring up to take all the slack out of the bottom run of the short 'B' chain. While holding that forward rotational pressure on the crankshaft, just nip up the pinch bolt on the front of the cylinder head, then do up the lock nut. They just need to be nipped up firm. Not too tight at all.
If, after doing this, you still have noises coming from the middle of the rocker cover, you may be up for a set of oversize Oldham coupling joints to join the pairs of cam shafts