This repair and service manual covers Honda CB650 SOHC Fours , including:
Honda CB650Z, U.K. 1978-1982
Honda CB650SC Custom, U.K. 1982-1984
Honda CB650SC Nighthawk, U.K. 1982-1984
Honda CB650Z, U.S. 1979
Honda CB650A, U.S. 1980
Honda CB650 Custom (CB650CA), U.S. 1979-1980
Honda CB650B, U.S. 1981
Honda CB650 Custom (CB650CB), U.S. 1981
Honda CB650C, U.S. 1982
Honda CB650SC Nighthawk, U.S. 1981-1982
Book Excerpt: 1978-1984 Honda CB650 SOHC Fours Repair Manual
ROUTINE MAINTENANCE
FRONT FORK OIL RENEWAL
When the action of the front forks become soft or spongy (ie. diving too much under heavy front wheel braking) or the damping feels weak, then the fork oil is due for replacement.
Note that these systems can also be caused by worn or damaged internal components, but by changing the fork oil prior to investigative dismantling, a lot of unnecessary work may be avoided.
Prise out the caps from the fork top bolts. This is not easy with the fork legs in their normal position, because the handlebars obstruct the bolts.
The easiest method is to slacken the pinch bolts in the upper and lower yoke, slide the stanchion down about 3 inches, then tighten the lower pinch bolts. Slacken and remove top bolt using the appropriate hexagon socket key.
If this is unavailable a suitable alternative can be found in a hexagon head bolt of the required size, inserted into a socket spanner. Release the top bolts carefully. DO not forget to remove the spring top seats, fitted below the top bolts, prior to refilling.
Place a suitable container below the drain bolt to the rear of each lower leg and remove each bolt. Allow the fork oil to drain, compressing the suspension slightly to drain the oil fully.
Re-install the drain bolts, checking that the copper sealing washers are refitted, and refill the forks, using ATF (Automatic Transmission Fluid). Do not overfill.
Refit and tighten the fork top bolt in the reverse manner of that described for removal.
FRAME AND FORKS
FOOTRESTS: EXAMINATION AND RENOVATION
The footrests are the swivel type and retained by a clevis pin secured by a split pin. The advantage of this type of footrest is that if the machine should fall over the footrest will fold up instead of bending.
If the footrests are damaged in an accident, it is possible to dismantle the assembly into its component parts by detaching each footrest from the rod and separating the folding rubber from the main support on which it pivots by withdrawing the split pin and releasing the clevis pin through the pivot.
It is preferable to renew the damaged parts, but if necessary they can be bent straight by clamping them in a vise and heating to a dull red with a blow lamp whilst the appropriate pressure is applied. Never attempt to bend the footrest straight whilst they are still attached to the frame.
If heat is applied to the main footrest support during any straightening operation, it follows that the footrest rubber must be removed temporarily to prevent damage from heat.
