1. The engine must be completely cool for this maintenance procedure, so let the machine sit overnight before beginning.
2. Remove the fuel tank and the air duct on XL600V and XRV750-L to N (1990 to 1992) models. Remove the fuel tank and the air filter housing on XL650V and XRV750-P models onward (1993-on). Refer to Chapter 4 for details.
3. Either displace or remove the right-hand radiator (not necessary if working on rear cylinder only).
4. 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). Check the condition of the cap O-rings and discard them if they are damaged, deformed or deteriorated.
16.4. Remove the crankshaft end cap (A) and the timing inspection cap (B)
5. Remove the valve inspection caps/covers from each valve cover - the caps (above the exhaust valves) can be unscrewed using a suitable spanner or socket, while the covers (above the inlet valves) are secured by two bolts (see illustrations). Check the condition of the cap and cover O-rings and discard them if they are damaged, deformed or deteriorated. Unscrew the spark plugs to allow the engine to be turned over easier (see Section 5).
16.5a. Unscrew the caps using a spanner on the hex (arrowed)
16.5b. The covers are secured by two bolts (arrowed)
6. Starting with the front cylinder, rotate the engine anti-clockwise using a suitable socket on the alternator rotor bolt until the line next to the 'FT mark on the flywheel aligns with the notch in the timing mark inspection hole (see illustrations). At this point make sure that the cylinder is at TDC (top dead centre) on the compression stroke (and not the exhaust stroke) by checking for some free movement between each rocker arm and the valve. There must be freeplay evident in all three rocker arms. If not, turn the engine anti-clockwise through one full turn (360°) until the 'FT mark again aligns with the notch. There should now be freeplay in all rocker arms indicating that the engine is correctly positioned.
16.6a. Turn the engine anti-clockwise using a socket on the timing rotor bolt...
16.6b ...until the line next to the FT mark aligns with the notch
7. Insert a feeler gauge of the correct thickness (see Specifications) between each rocker arm adjusting screw and valve and check that it is a firm sliding fit (see illustration). If it is either too loose or too tight, slacken the locknut and turn the adjusting screw in or out as required until a firm sliding fit is obtained, then tighten the locknut to the torque setting specified at the beginning of the Chapter, making sure the adjusting screw does not rotate as you do so (see illustration). Re-check the clearances. not forgetting that on most models there is a difference between the inlet valve clearance and the exhaust valve clearance. On completion turn the engine anti-clockwise two full turns (720°), then align the marks so it is at TDC on the compression stroke as before and recheck the clearances.
16.7a. Insert the feeler gauge between the base of the adjusting screw and the top of the valve stem as shown
16.7b. Slacken the locknut using an offset ring spanner and turn the adjusting screw using pliers
8. Moving to the rear cylinder, rotate the engine anti-clockwise using a suitable socket on the alternator rotor bolt until the line next to the 'RT' mark on the flywheel aligns with the notch in the timing mark inspection hole (see illustration). At this point make sure that the cylinder is at TDC (top dead centre) on the compression stroke (and not the exhaust stroke) by checking for some free movement between each rocker arm and the valve. There must be freeplay evident in all three rocker arms If not. turn the engine anti-clockwise through one full turn (360°) until the 'RT' mark again aligns with the notch. There should now be freeplay in all rocker arms indicating that the engine is correctly positioned. Check and adjust the valve clearance as described in Step 7.
16.8. Turn the engine until the line next to the RT mark aligns with the notch
9. Install all disturbed components in a reverse of the removal sequence, referring to the relevant Chapters where necessary. Install the valve inspection caps and covers using new O-rings if necessary, and smear the O-rings with clean oil (see illustration). Install the crankshaft and timing inspection caps using new O-rings if necessary, and smear the O-rings with clean oil (see illustration). Apply a smear of molybdenum disulphide grease to the threads of the caps and tighten them securely.
16.9a. If necessary use new O-rings on the valve caps and covers ...
16.9b ...and the inspection and end caps