NB: These instructions are given for guidance only and cannot engage the author's liability in the event of misinterpretation, failure to assess the vehicle's actual condition and/or non-conformity, unsuitable mechanical practice or the use of inappropriate tools.
Fitting the timing chain — 750
- Take the opportunity of replacing the chain to check the nylon rollers (guide and tensioner). Replace them if excessively worn, or if the special plastic is breaking up or cracking.
- Always remove the chain tensioner before removing and refitting the chain.
- Plug the head passages with rags so the split link cannot fall into the crankcase.
- Check that the TDC mark is accurate (old engines). Methods: dial gauge, or piston stop — with the stop fitted, gently turn the engine in the running direction until the piston stops and mark the freewheel against the case, then turn the opposite way until it stops and make a second mark; TDC is exactly midway between the two marks.
- Especially with a new head gasket, the chain may look over-tight: fit spacers on the studs and torque the head down to seat it and compress the gasket.
- Once the chain is assembled (open side of the split link facing away from the running direction), turn the engine two or three times by hand to check the timing. Remove the head nuts and spacers, refit the cam cover. Fit new or annealed 2 mm special copper washers. Tighten the head cap-nuts a quarter-turn at a time, crosswise from the outside, to a final torque of 5 m·kg. Refit the chain tensioner.
- Tension: turn the engine by hand for several revolutions and note when the tensioner rod is at its furthest out; at that exact point, lock the spindle clamp screw and its lock-nut. With new gaskets (head and cam cover) the chain may be tight for the first few kilometres; redo the chain-tension adjustment together with the head re-torque, after 300-500 km.