AJS & Matchless Owners Club

East Suffolk Section

Technical Tip (18) Replacing Early Twin Cylinder Heads

1. Put engine into high gear so as to use the rear wheel for turning the engine.

2. Right-hand cylinder: turn engine to compression t.d.c. (inlet pushrod has just gone down and piston is at t.d.c.); fit head, taking care to ensure rockers are in the pushrod cups; finger tighten the cylinder head nuts (with spacers and washers underneath!)

3. Turn engine forward so that left-hand piston is at compression t.d.c. and proceed as above.  This ensures minimum strain on head nuts that would have occurred  if tightened against valve spring pressure.

4. Fit manifold and fully tighten manifold nuts

5. Working in a diagonal pattern torque cylinder head nuts to 22 foot pounds

When the bike is fully re-assembled start engine and run until warmed up but not too hot.  Re-torque nuts to 22 foot pounds.  Leave engine to cool over night.  Gently ride bike for 100 miles then torque down the nuts again to 22 foot pounds.  Final re-torque after 500 miles.