Adjusting Moto Guzzi valves is a fairly easy job. Here’s what you have to do for a basic valve adjustment:
1. Make sure the engine is cold; best to do this first thing in the morning after the bike has been sitting all night.
2. Place the bike on the centerstand.
3. Shift to the highest gear you can get it in; sometimes it helps to jog the rear wheel with one hand as you push the shift lever to get it in gear.
4. Take off the alternator cover.
5. Put a socket wrench on that big alternator nut, I think it’s a 23mm. I know a 15/16″ will work as well.
6. Remove both valve covers and spark plugs.
7. If you know the heads do not need re-torquing, skip to step 14.
8. Take off the rocker arms. They are held in place by a shaft, which is held in place with an 11 mm hex-head. When removing the rocker arms, go slow. There is a washer, spring, and another washer on top of each rocker arm. One washer is copper, one is steel. Pull the arm out too fast, you will lose parts like I did. Also, BEFORE YOU PULL THE LAST ROCKER ARM OUT, note the order of the washers. I think bottom to top, it is steel washer, spring, copper washer.
9. There are 6 head bolts per cylinder: two under each rocker arm, one under the 10mm hex cap at the top of the cylinder, and one by the spark plug. Use a long 10mm Allen key w/ an adjustable (Crescent) wrench to open that cap. It is not reverse threaded, mine was tight as hell.
10. Loosen all 6 of the head bolts just a little bit to break them. Use a torque wrench and in a criss-cross pattern, tighten them to 30 foot pounds. Go ahead and do the other cylinder.
11. Leave the head bolts at 30 foot pounds overnight.
12. After leaving for at least a few hours, in a criss-cross pattern, tighten each head bolt to 35 foot pounds.
13. Re-install the rocker arms.
14. Remove the rubber cover (the one that’s about the size of a quarter) on the right hand side of the engine so you can see the flywheel timing marks.
15. Turn the rear wheel in the direction of normal travel.
16. Note the direction that the alternator nut rotates.
17. Put your thumb over the spark plug hole.
18. Rotate the alternator nut in the direction of normal travel as noted above. Rotating it backwards will not break anything, but you will not get a good valve measurement because of slack in the valve train.
19. When you feel it pressing air out against your thumb, begin to look in the timing hole (where the rubber cover was) for the “S” (if your thumb is in the left spark plug hole) or the “D” if you are on the right cylinder.
20. Line up the “S” (Left cylinder) or “D” (Right cylinder) flywheel marks, loosen the lock nut on the intake or exhaust, adjust the gap and tighten the lock nut. Repeat for other valve on the same cylinder (* See note below).
21. Repeat for other cylinder.
22. Use 8 foot-pounds of torque for the valve cover bolts.
23. Put your plugs, covers & wires back. make sure to get that socket off
your alternator nut before starting so you do not ding your fender.
NOTE: * If you have doubts about the S & D marks’ accuracy, GENTLY use a screw driver or other probe in the spark plug hole while SLOWLY rotating the 23mmm alternator nut. Mine were accurate, and Guzziology does not mention
this inaccuracy, BUT, it is easy enough to check. Just be careful. You do not want to ruin a perfectly good screw driver!
Special thanks to Winter Colby, Lowside, and Guzzi Godfather Wayne Orwig!