Twin cylinder head camshaft and valve gear

The cylinder head must be removed from the machine if you are to work on any of the components hidden within it. It can be removed once the engine is hinged forward while still in the frame, or with the engine on the bench.

To remove the cambox cover, first disconnect the breather pipe from the breather valve. This is held by a conventional hose clip and is a push-on fit. Once it's off it's a good idea to unscrew and remove the breather valve. This is a plastic connector which screws in the alloy casting. Inside is a plastic ball valve which can be picked out. Two tvpes of valve have been used, the later type can be retrofitted. Clean the whole thing inri:;- -g the breather pipe with a degreaser. Loosen progressively the eight cylinder head nuts ate machines use yellow plastic covered nuts — these prevent oil seepage up the stud), starting with the outside nuts so to avoid cambox cover distortion. Lift off the cambox cover with its gas*e~ On the underside of the cambox cover are two tin 'shields' which are bolted up. These car be removed for cleaning. Now you must split the camchain. Remove the dynamo cover and r: ate the engine until the spring link is visible on the top of the duplex cam sprocket. You can turn the engine either on the crankshaft nut or with the dynamo belt. Go to the back of the barrel and loosen the camchain tension at the adjuster (see the Maintenance section) and then remove the acrnster body complete by removing the four fixing bolts.

Very carefully remove the camchain spring link (the chain is now 'loose" because the adjuster has been removed). Using two pieces of wire hoe* each end of the camchain and tie the chain ends back. Watch you don't drop pieces of cam: ran into the cylinder head.

The camchain adjuster is a simple instrmer: It is best explained by looking at the exploded diagram of its components. It is norma-. a very reliable instrument which requires little maintenance. Sometimes the tensioner wheel aeeca replacement after considerable wear, and that is obvious and easy. A damper wheel sits is the centre of the camchain, inside the barrel and that can only be removed by removing the barrel F; rtmately that too is very reliable. The damper and tensioner wheels are made of nylon anc m_i ~ mn cleanly on the rollers of the duplex camchain.

NOTE: If a chain link or any other sna_ ccimccnent falls into the cylinder head and down into the crankcase, it can sometimes be removed :, . tosening and removing the oil filter and recovering whatever it is from below.

NOTE: The SFC 'big' damper wheel rura :r a needle roller.

NOTE: If all you are doing at this stage :: replace the camchain, then link up the new chain to the old and carefully pull it through. Leave a rttie tension on the old chain so that when pulling through, the chains do not jam (they cam : • _mc the sprocket on the crankshaft). If the chain does jam, then carefully turn the engine back * ar ea while lightly manipulating both chain ends until the chain is free again. Always fit a new spring ^.k. however. Carefully examine the chain for wear, on its outer sides. If 'shiny' wear appear; :: means that the outer rings of the central crankshaft bearings have been touching the chain A . ■ » ng plate in the upper crankcase half should prevent this. To examine this and fix it, you must spl.t the crankcase. The locking plate can be centre punched to hold it.

To remove the cylinder head you mus: now remove the nuts and washers which are placed just below the spark plug holes (first remove the cam covers, remove the plugs, then replace them) and a small bolt at the centre rear of the heac Break the cylinder head joint without disturbing the barrel (unless you subsequently wish to remove that too). You can tap the head with a hide-headed hammer on a solid part, but be careful. Now craw the head up its studs holding the two camchain end wires, making sure that they pass down through the tunnel. Once the chain ends can be drawn through in full under the head, tie the wires to convenient parts of the crankcase, and then pull off the head.

You now have a cylinder head complete with all valve gear and camshaft.

To further dismantle the cylinder head, you must observe a strict order of component removal. It goes — rocker spindles, rockers and then valves or camshafts and camshaft sprocket.

To remove the rocker spindles and rockers, first place the cylinder head on a bench and somehow try to hold it, combustion chamber side down. A little wooden frame cut to shape will help, as would a large, soft-jawed vice.

Laverda 650 VicenzaLaverda 650 Vicenza

The Twin crankcase. oil filter and crankcase side covers with the primary drive cover on the left. (SFC components differ slightly)

Laverda 650 Vicenza
Twin crankshaft and pistons with the starter freewheel on the far right. (SFC crankshafts are different as are the
Cylinder Head Laverda

Remove both camshaft end covers — each one is fixed with four bolts. You can leave the rev counter drive intact. Remove each of the tappet adjuster covers and slacken each of the four adjusters right off. (These end covers are already off to enable cylinder head removal].

NOTE: The rev counter drive is a single device fixed by a conventional screw. It is sealed by an O ring.

Now you must use Laverda's rocker spindle extractor tool (61818978) to extract each of the four spindles. Before you tackle each spindle, make sure the rocker in question is not under tension — it must be riding on the base circle of its cam. That way you won't bend anything! Don't be frightened of warming the head for a couple of minutes in a hot oven to help (maximum temperature of 100°C).

Once the spindles are free then the rocker arms can be removed through the top of the head. Note the spindle and rocker positions — they must be replaced in the same place.

Wear of the bronze bushes in which the rocker spindles run is slow. If these bushes are shot, then you must seek expert advice as to their renewal. Bushes are listed as spare parts. Strip the head fully before anyone looks at it. Sometimes the spindles themselves wear, and running tolerances are given in the Specifications If the rocker arms themselves have wear grooves in their rubbing surfaces, then they must be replaced. Light scratching is, however, normal.

Cylinder Head Laverda

The Twin's camshaft halves are bolted togs' through the sprocket

Drive out the camshaft half bearings this way (Twin)

The Twin's camshaft halves are bolted togs' through the sprocket

Drive out the camshaft half bearings this way (Twin)

Cylinder Head Laverda Triple

The two bolts are through the flange which bolts onto the camshaft sprocket (Twin)

Cylinder Head Laverda

The Twin's camshaft chain ends should be wired at this stage

The two bolts are through the flange which bolts onto the camshaft sprocket (Twin)

The Twin's camshaft chain ends should be wired at this stage

For valve and valve spring removal and checking see the sub-section after the Triple's cylinder head removal.

NOTE: You cannot make an SFC head out of another model's — it's a different casting. Camshaft and camshaft sprocket removal is fiddly. You need a pair of very good quality 9mm ring spanners and the Laverda camshaft extractor tool (61818974). However, early Twins do not have the facility to use the extractor tool so you have to tap out the camshaft — both methods will be explained as the second method can be used on the later machines too.

Using both 9mm spanners remove the nuts which hold the two camshaft flanges to the camshaft sprocket. There is little room to move here — the spanners must be slim but they must also be 'ringers' because open-enders will wreck the nuts. Now use the Laverda extractor if you have one on the right camshaft half. If not, carefully tap the cam through using a soft drift. You must hit the steel ball bearing not the cam lobes or flange. You are trying to extract the camshaft half complete with both bearings and flange. Tap very carefully for if the inner bearing passes through the housing of the outer bearing at anything other than straight and square, you could wreck the cylinder head! Again a little oven heat could help.

Remove the camshaft sprocket and then remove the other camshaft by tapping it out as just described.

You can draw or tap off the bearings from the camshaft halves if you use great care. Remember that the camshaft halves, flanges and sprocket are keyed together so that they can't be assembled incorrectly. The key is a push fit between them all. The left hand camshaft half is the one with the worm drive for the rev counter. The camshaft sprocket — mark the bearings so that they can be replaced in their original places.

For detailed checking of the camshaft, sprocket and cylinder head, see the sub-section after the Triple's head removal.

Assemble the valves into their guides using a valve spring compressor. Once each valve is assembled with its springs, seat and collets turn the head over and test its seating by pouring a little petrol into the combustion chamber and see if it slowly rims away — if it does, then you must re-grind the valve to the seat. It must be 'gas' tight.

With all four valves assembled, heat the head in a domestic oven to 90-100°C to expand the metal (do not overheat). Then offer up the left hand camshaft (rev counter drive) complete with bearings into the head (tapping it gently and squarely) so as not to damage the cam lobe or bearing housing. Place the cam sprocket into the tunnel of the head with it's timing mark on the right hand side, i.e. opposite the camshaft coming into the head (rev counter drive half). Ensure that the cam engages with the flange and cam sprocket with the key in its centre. Now fit the other camshaft half into the other side of the head (right side). Remember that the three studs must be placed in the sprocket before fitting the left hand camshaft. They won't enter afterwards.

Fit the right hand side's flange and marry-up-cam to the key, flange and cam sprocket. Fit all three cam sprocket studs and nuts together with their locking washers. Use Loctite too. Use those two 9mm ring spanners and do the nuts up as tight as you can with your hands. Before you finally tighten the eight nuts, in a diagonal and progessive manner, make sure all eight camshaft ball bearings are correctly seated in their housings and that the cams run smoothly. Squirt some oil into the ball bearings. Make sure the camshafts are really in the 'middle' of the cylinder head. If not, either of the outer cambearings will be too far out, in which case that side's cam end cover cannot be tightened fully home and oil will leak on that side.

Now fit the rockers and their spindles — first oil each of their bushes.

Remember that the rockers and their spindles are identical, but that they should be refitted in their original positions. Check that the oil feed hole in each rocker is clear. Oil the spindle liberally before refitting. With the head still warm you should be able to fit the spindles and rockers — care must be taken so that the cam lobes are not damaged. Remember that the rocker must be on the base circle of the cam lobe as it is pushed home. A slot is cut in the end of each rocker spindle to enable you to twist it so as to align it so that the adjacent cylinder head stud can pass through. This will be obvious when you look at it. The spindle should be turned with a flat bladed screwdriver but only with the head still warm. Now refit the camshaft end covers.

If you wish, with the cylinder head COLD, you could set the tappet clearances safely and easily.

To refit the cylinder head; wait until it is COLD. Clean the fitting edges of the barrel and fit a new gasket. It can only be placed one way around, and there is only one type available.

Still holding the cam chain ends, duly wired, turn the crankshaft until the PM mark on the starter freewheel aligns with the mark on the crankcase. It may be necessary to loosen the cam chain to allow the crankshaft to turn independently. The cylinder must be truly vertical for the cam chain to be free of the lower sprocket. Do not loosen the chain ends. For that operation and the next few you will need the help of an assistant. Now fit the head, sliding it down the studs, at the same time carefully guiding the cam chain ends up through the head and around the camshaft sprocket. Push the head right down onto the gasket Now turn the camshaft sprocket until the mark on its right hand side aligns with the mark on the top side of the cylinder head, but without disturbing the camshaft chain ends. Now pull the two ends of the camchain up fully out of the head and lay them over the sprocket until they are close to oimng. i.e. they are but a spring link away from each other. (If the chain will not meet, then the hea ; is not down on the barrel fully. Give it a light tap with a hide-headed hammer). Stuff the head : ^nnels with rag before fitting the spring link and removing the wire ends — this way nothing fails down into the crankcase. Fit the spring link complete with the closed end of the spring link feeing forward. Refit the chain adjuster using a new gasket and some sparingly used soft gas*e- rement. Tighten the body but set its tension at its loosest as you do so. Once fitted, loosen the adjustment and let the tensioner tension, but do not lock it. The chain is correctly fitted when you lave turned the crankshaft so that the two camshaft marks just mentioned align, when those on ire starter freewheel and the crankcase do so, and vice versa.

Replace the cambox cover using a new gasket and some sparingly used soft setting gasket cement. Replace the cylinder head nuts anr * ashers and tighten them. Tighten them progressively and in the order given on the accompanying diagram. Final torque should be 36 ft.lb., and no more. Finally fit the two side nuts and washers elm» to the spark plug holes and the rear one above the cam chain tensioner.

The cam chain cannot be finally tensianec until the head is properly torqued down. Read about this in the Maintenance section.

After around 300 miles use you should re-torque the head. This can be done with the engine in the frame as follows. Remove the fuel tans , and remove the two top studs which fix the engine to the top frame tubes. Torque them all in the proper order. The best tool for this job is a 17mm crow's foot spanner and a 'clicking' type of torque wrench. Effectively there is no other method.

Laverda 650 Vicenza
align
Cylinder Head Laverda Triple Cylinder Head Laverda Triple

1 Slide in the connecting link as shown

Cylinder head nut tigtening sequence on the Twin

Make sure the spring link heads the directional arrow

1 Slide in the connecting link as shown

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  • KRISTIAN
    How to remove cambox on a 400 honda shadow?
    5 years ago

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