CB650SC/New Owner Suggestions

Engine

Should replace

O-rings

Avoid fuel leakage:

• Carb "Fuel-Tee" x2
• Carb bowl seal x4
• Carb fuel tubes & "Vent-Tees" x8(x2+x2+x2+2)

Avoid Air leakage(leads to lean):

• Carb-to-insulator-to-head x8(x2+x2+x2+2)

Avoid low head/cam/tappet lubrication/valve tick:

• Valve-train oil pipe x10(x2+x8)

Avoid low oil pressure/dirty oil contamination?:

• Oil filter tube x3?
• Oil filter cover x1 (sometimes comes with new filter, can be reused carefully)

Must clean/rebuild

Carburetors

• Check and replace with same main and pilot jets (order individually by size, no kits)
  • -or- clean, check, and reuse originals
• Clean, check, reuse emulsion tube and needle (do not trust "kits")
• If a po crushed the mixture screw seats, tuning will go from 2-3 turns out to something like 1/4-3/4 of a turn out
  • The hole that the very tip of the mixture screw "needle" goes into should have a narrow, raised "lip" surrounding it. If you look down the mixture screw hole, and see a "pin-hole" that is flush to the base or has "starred" out metal around it that looks like a pressed rivet, the mixture seat is crushed and destroyed.
• Do NOT trust kits! Get OD:5mm Cross-Section: 1.2mm (Honda OEM OD:5mm CS:1.1mm) FKM o-rings for the idle enrichment screws
  • Pre-soak the fresh o-rings in gasoline, fully immersed, for 15 minutes, before installation
  • Add a drop of light oil to the o-ring and washer
  • Set screws to 2-1/2 turns out from lightly seated
• If you don't have and can't get "EPA"/back-out lock caps for the mixture screws, they -will- back out and lead to fouled plugs
  • 3D printed replacements do exist and can be thread locked on just like the originals
  • In desperate situations a spot end-to-end, around the threads bead of white, high-temperature, fuel-safe thread sealer can be used to secure the screws AFTER reading the spark plugs to confirm the tune
    • Blue thread locker will loosen from engine heat even though the carbs get cold
    • Red thread locker will be a huge mistake
• It goes without saying, vacuum-balance the carbs
  • Nothing beats digital gauges for speed, ease of use, or accuracy.

Hydraulic Tappets

• Follow manual for removal
• Use allen key (my recommendation), smooth bore side of 1/16 drill bit (Clymer manual), or special tool Honda 07973-ME9-0000 to bleed out oil
• again bleed upright under kerosene (mineral spirits or maybe even diesel fuel in a pinch?) to clean
• bleed out the solvent from the last step
• bleed under engine oil until primed (pressing on the tappet without the "bleeder pin" inserted should feel like it is basically completely solid
• Keep upright and install with the tappet lower hole toward the centre (toward spark-plugs) squirter hole

Hydraulic control systems

Brakes

• Brake callipers will corrode and seize in place, essentially locking the wheel if left unmaintained
  • soaking in PB Blaster for days and 100psi from the air compressor may be necessary to dislodge the pistons
  • soaking in PB Blaster and wailing upon with a punch and 1/2lb hammer may be necessary to remove the retaining pins