Camshafts and rockers — removal, inspection and installation (Honda XRV750)

0

Note: The camshafts and rockers can be removed with the engine in the frame.

Removal

1. Remove the valve covers (see Section 8).

2. If the belly pan on your model obscures the alternator cover, remove it (see Chapter 8). Unscrew the crankshaft end cap and the timing mark inspection cap from the alternator cover (see illustration). Using a suitable socket on the alternator rotor bolt (see illustration), rotate the engine anti-clockwise so that it is at TDC (Top Dead Centre) on the compression stroke of the cylinder being worked on. At TDC the line next to the 'FT' mark (if removing the front camshaft) or the 'RT' mark (if removing the rear camshaft) should align with the notch in the inspection hole (see illustrations), the index lines on the camshaft sprocket should align with the top of the cylinder head mating surface and the TDC indicator notch on the sprocket end of the camshaft should be on the top (see illustration), and both camshaft lobes should face down. If not, turn the engine anticlockwise through one full turn (360°) until the line next to the 'FT' or 'RT' mark again aligns with the notch - the marks should now all align as described indicating the engine is at TOC on compression.











3. At this point, measure the amount of projection of the thick wedge on the top of the cam chain tensioner (see illustration). If the amount of projection exceeds the limit specified at the beginning of the Chapter, the cam chain must be replaced with a new one (see Section 10). Having taken the measurement, push the thick wedge down using a screwdriver and simultaneously pull the thin wedge straight up using a pair of pliers and secure it in position using a 2 mm pin inserted through the hole in the wedge (see illustrations).









4. Unscrew the two bolts securing the end camshaft holder adjacent to the cam chain sprocket and remove the holder, noting which way round it fits (see illustration). Remove the two dowels if they are loose.



5. Rotate the engine 360° anti-clockwise to reveal the lower sprocket bolt and remove it, then return the engine to TDC on the compression stroke by rotating it another 360° anti-clockwise, and remove the other sprocket bolt (see illustration). Use the socket on the alternator rotor bolt to stop the engine rotating while unscrewing the sprocket bolts.

Caution: Do not rotate the camshaft after the cam chain has been disengaged as damage may occur if a valve contacts a piston. The crankshaft can be rotated as long as the valves are closed or if the camshaft has been removed.

6. Unscrew the bolts and the nuts securing the main camshaft holder (see illustration). Slacken them evenly in a criss-cross pattern, then remove the holder along with the oil guide plate, noting any washers and how the assembly fits (see illustrations). Retrieve the two dowels if they are loose. Mark each holder according to its cylinder (i.e. front or rear).







7. Slip the sprocket off its boss on the camshaft (see illustration). Remove the camshaft, then slip the cam chain off the sprocket and remove the sprocket (see illustration). Tie the cam chain up to prevent it from dropping down into the crankcase, and do not allow it to go slack as it could bind between the crankshaft sprocket and the crankcase. Cover the top of the cylinder head with a rag to prevent anything falling into the engine. Mark each camshaft and sprocket according to its cylinder (i.e. front or rear). On most models the camshafts come with their cylinder identity already marked on the sprocket end of the shaft - 'F' for the front cylinder and 'R' for the rear, though on XL600V-H and J (1987 and 1988) models a thicker section in the camshaft Is used to identify the front cylinder shaft. Check that the marks are visible and make your own if necessary). Note the 'IN' mark on the sprocket which must face inwards on installation.





8. If necessary, remove the rocker arm shafts from the camshaft holder, using a screwdriver to poke them out (see illustration). If the shafts are difficult to remove, turn them using a screwdriver in the slot in the end then drift them out. Remove the rocker arms and their wave washers, noting how they fit (see illustration). Mark each shaft and rocker arm according to its position (i.e. front or rear cylinder, intake or exhaust valve), and/or install each rocker arm back onto its shaft in its original position, along with its washers.

Note: Before renewing the camshafts or the cylinder head and camshaft holders because of damage, check with local machine shops specialising in motorcycle engineering work. In the case of the camshafts, it may be possible for cam lobes to be welded, reground and hardened, at a cost far lower than that of a new camshaft. If the bearing surfaces in the cylinder head are damaged, it may be possible for them to be bored out to accept bearing inserts. Due to the cost of a new cylinder head, it is recommended that all options be explored.

9. Inspect the bearing surfaces of the camshaft holders and cylinder head and the corresponding journals on the camshafts. Look for score marks, deep scratches and evidence of spalling (a pitted appearance). Chock the oil passages for clogging.

10. Check the camshaft lobes for heat discoloration (blue appearance), score marks, chipped areas, flat spots and spalling. Measure the height of each lobe with a micrometer and compare the results to the minimum height listed in this Chapter's Specifications (see illustration). If damage is noted or wear is excessive, the camshaft must be replaced with a new one.



11. Check the amount of camshaft runout by supporting each end on V-blocks, and measuring any runout using a dial gauge. If the runout exceeds the specified limit the camshaft must be replaced with a new one.

12. Next, check the camshaft journal oil clearances. Clean the camshaft and the bearing surfaces in the cylinder head and camshaft holders with a clean lint-free cloth, then lay the camshaft in its correct location in the head with its lobes facing down (see Step 7) - there is no need to fit the sprockets or rocker arms (if removed).

13. Cut strips of Plastigauge and lay one piece on each bearing journal parallel with the camshaft centreline, making sure none is placed over the oil hole. Make sure the camshaft holder dowels are installed and fit the holders (see illustrations 9.28a and 9.4). Ensuring the camshafts are not rotated at all, install the holder bolts and nuts with any washers and tighten them evenly and a little at a time in a criss-cross sequence to the torque settings specified at the beginning of the Chapter (see illustration 9.6a).

14. Now unscrew the bolts and nuts evenly, a little at a time, in a criss-cross sequence and carefully lift off the holders, again making sure the camshaft is not rotated.

15. To determine the oil clearance, compare the crushed Plastigauge (at its widest point) on each journal to the scale printed on the Plastigauge container.

16. Compare the results to this Chapter's Specifications. If the oil clearance is greater than specified, measure the diameter of the camshaft bearing journal with a micrometer. If il is within specifications, replace the cylinder head and cam holders with new components. If the |ournal diameter is less than the specified limit, replace the camshaft with a new one and recheck the clearance. If the clearance is still too great, also replace the cylinder head and cam holders. Before replacing any worn parts with new ones, bear in mind the information in the note preceding Step 9.

17. Except in cases of oil starvation, a cam chain wears very little. If a chain has stretched excessively, which makes it difficult to maintain proper tension, it must be replaced with a new one (see Section 10).

18. Check the sprocket for cracks and other damage, replacing it with a new one if necessary. Note that if a new sprocket is installed, a new cam chain must also be installed. If the sprockets are worn, the cam chain is also worn, and also the sprocket on the crankshaft (which can only be remedied by renewing the crankshaft). If wear this severe Is apparent, the entire engine should be disassembled for inspection.

19. If available, blow through the oil passages in the rocker arms and camshaft holder with compressed air. Inspect the rocker arm contact points for pitting, spalling, score marks, cracks and rough spots. If the rocker arms are damaged they must be replaced along with the shafts as a set.

20. Check the condition of the wave washers and replace them if they are damaged or deteriorated.

21. Measure the diameter of the rocker arm shafts in the area of contact with the rocker arms (see illustration). Also measure the internal diameter of the rocker arm bores (see illustration). Compare the measurements to the specifications listed at the beginning of the Chapter. If any components are worn beyond their limits, replace all the shafts and arms as a set.

Installation

22. If removed, apply a smear of molybdenum disulphide grease to the contact faces of each rocker arm. then install the arms and their wave washers into the camshaft holder, making sure they are returned to their original positions (see illustration). The wave washers fit on the inside of the intake rocker arms, and on the left-hand side of the front cylinder exhaust rocker arm, and the righthand side of the rear cylinder exhaust arm. adjacent to the triangular mark on the holder (see illustration).





23. Apply a smear of molybdenum disulphide grease to the rocker arm shafts, then slide the shafts into the camshaft holder, making sure they are installed In their original positions, and that they pass through the rocker arms and wave washers (see illustration). Position the shafts so that the grooves in the ends of the shafts are vertical and the holes in the shafts align with the boll holes in the camshaft holder (see illustration). Check that the arms move freely on the shafts.





24. If only the front camshaft has been removed, position the crankshaft at TDC on the compression stroke for the rear cylinder (see Step 2), then rotate the crankshaft anticlockwise 488° (at which point the 'FT' mark on the rotor will align with the notch in the inspection hole). This positions the front cylinder at TDC, and the front camshaft can be installed. If only the rear camshaft has been removed, position the crankshaft at TDC on the compression stroke for the front cylinder (see Step 2), then rotate the crankshaft anti-clockwise 232° (at which point the 'RT' mark on the rotor will align with the notch in the inspection hole). This positions the rear cylinder at TDC. and the rear camshaft can be installed. If both camshafts have been removed, Install the front one first, with the crankshaft positioned so that the 'FT' mark on the rotor aligns with the notch in the inspection hole, then rotate the crankshaft anti-clockwise 232° (at which point the 'RT' mark on the rotor will align with the notch In the inspection hole). This positions the rear cylinder at TDC on the compression stroke, and the rear camshaft can be installed.

Caution: Keep the cam chains taut when rotating the crankshaft.

25. Check that the cam chain Is engaged around the lower sprocket teeth on the crankshaft and that the crankshaft is positioned as described in Step 24. Apply a smear of molybdenum disulphide grease to the camshaft journals. Position the camshaft sprocket with the sprocket's 'IN' mark facing inwards, the index lines on the sprocket aligning with the cylinder head mating surface, and its mounting holes at top and bottom (see illustration). Keeping the front run of the cam chain taut, engage the chain on the camshaft sprocket teeth (see illustration 9.7b). Install the correct camshaft for the cylinder being worked on; the one with a thicker mid section (XL600V-H and J models) or marked 'F' (all other models) is for the front cylinder, the one without the thicker section or marked 'R' is for the rear cylinder. Fit the sprocket onto the camshaft and align the bolt holes (see illustration 9.7a), and position it so that the TDC indicator notch on the sprocket end of the camshaft faces up (see illustration 9.2e) and the cam lobes face downwards (see illustration). Install the top sprocket bolt finger-tight only (see illustration 9.5). Check that the chain is tight at the front of the engine so that there is no slack between the crankshaft sprocket and the camshaft sprocket, and that all marks are still correctly aligned (see Step 2). If any slack is evident, move the chain around the sprocket so that the slack is taken up (see illustration). Any slack in the chain must lie in the portion of the chain in the back of the cylinder so that it Is then taken up by the tensioner.







26. Before proceeding further, check that everything aligns as described in Step 2. If it doesn't, the valve timing will be inaccurate and the valves will contact the piston when the engine is turned over.

27. Apply a suitable non-permanent thread locking compound to the camshaft sprocket bolt threads, then tighten the top bolt to the specified torque setting, using a socket on the alternator rotor bolt to stop the engine from rotating if necessary (see illustration). Rotate the crankshaft anti-clockwise 360° to reveal the lower sprocket bolt and tighten that to the specified torque setting, then return the engine to TDC on the compression stroke for the cylinder being worked on by again rotating it anti-clockwise 360.



28. If removed, install the main camshaft holder dowels into the cylinder head or holder (see illustration), then install the holder, making sure it is the right way round and seats correctly (see illustration 9.6c). Install the oil guide plate onto idle holder with its guide facing the intake valves (see illustration), then install the holder bolts and nuts with any washers, using new ones if necessary, and tighten them evenly and a little at a time in a criss-cross pattern to the torque setting specified at the beginning of the Chapter (see illustration 9.6a).





29. Before proceeding further, again check that everything aligns as described in Step 2. If it doesn't, the valve timing will be inaccurate and the valves will contact the piston when the engine is turned over.

30. If removed, install the end camshaft holder dowels into the cylinder head (see illustration 9.4). Install the holder, making sure its flat surface faces inwards and it seats correctly onto the dowels. Install the holder bolts and tighten them evenly to the specified torque setting.

31. With both holders tightened down, check that the valve timing marks still align (see Step 2). Check that each camshaft is free to rotate by turning it a few degrees in each direction using a suitable socket on the alternator rotor bolt. Lubricate the camshaft lobes with a mixture of engine oil and molybdenum disulphide grease.

32. Remove the 2 mm pin securing the thin wedge on the cam chain tensioner - the tensioner will automatically set itself (see illustration 9.3c).

33. Rotate the engine anti-clockwise through 720n degrees and re-check that the valve timing for both cylinders Is correct (see Step 2).

34 Check the valve clearances (Chapter 1) and adjust if necessary.

35. Install the crankshaft end and timing Inspection caps using new О-rings if necessary, and smear the О-rings with clean oil (see illustration). Apply a smear of molybdenum disulphide grease to the threads of the caps and tighten them securely.



36. Install the valve cover (see Section 8).

37. Check the engine oil level and top up if necessary (see Chapter 1).

See this article in russian language

Article about repair motorcycles «Honda Africa Twin XRV 750» (1989-2003): «Camshafts and rockers — removal, inspection and installation»: https://motoinstruction.ru/en/Honda/Africa-Twin/XRV750/engine/repair/115048 <a href="https://motoinstruction.ru/en/Honda/Africa-Twin/XRV750/engine/repair/115048">Camshafts and rockers — removal, inspection and installation</a> - article about repair motorcycles «Honda Africa Twin XRV 750» (1989-2003) from section «Engine repair». [url=https://motoinstruction.ru/en/Honda/Africa-Twin/XRV750/engine/repair/115048]Camshafts and rockers — removal, inspection and installation[/url] - article about repair motorcycles «Honda Africa Twin XRV 750» (1989-2003) from section «Engine repair».