Honda produced the 650 cc (honda service manual claims 627 cc, although "626cc" cast on motor) series inline four cylinder overhead cam street bikes as their last line of SOHC bikes made. It makes decent power for the aging SOHC technology and is still a sharp looking roadbike.

Below are the model variants as listed in the Haynes repair manual. While produced in the US until 1982, it appears the SOHC 650 continued overseas production until early 1984. I have also heard of a Japanese model, the CB650LC JAPAN, with a "Luxury Custom" emblem side cover. Maybe the luxury model didn't vibrate like hell at 70 mph or blow headgaskets. :)


The standard model had spoked rims, single front disk brake, and 4 into 2 exhaust. The custom models had comstar rims, dual front disk brakes, and 4 into 4 exhaust. The 1982 CB650SC was the Nighthawk, and had redesigned body paneling, a different seat, a black powder coated engine, and dual brake calipers in the front. Of course, there were many more changes, like the gas tanks, colors, forks, gauges, etc., I will eventually try to document them all. The engine itself went through no changes from '79 to '82. The gearbox had very slight changes, they are listed in the performance specs section.

GEARING IDENTIFICATION:

Gearbox Ratio Chart:
Custom and Nighthawk specifications are the same as the Standard Model unless otherwise indicated by a C=(Custom) or SC=(Nighthawk)

1979 1980 1981 1982
Primary Reduction 2.737 2.738 2.738 2.737
1st 2.500 2.500 2.500 2.692
2nd 1.722 1.722 1.722 1.778
3rd 1.333 1.333 1.333 1.333
4th 1.074 1.074 1.074 1.042
5th 0.885 0.885 0.885 0.885
Final Reduction: C=Custom, SC=Nighthawk 2.500 (16/40) 2.500 (16/40), C=2.438 (16/39) 2.500 (16/40), C=2.438 (16/39) 2.294 (17/39), SC=2.235 (17/38)
Drive Chain: C=Custom, SC=Nighthawk RK50NK or DID 50HDK, 102 links RK50NK or DID 50HDK, 104 links RK50MO or DID 50V, 104 links RK50MO or DID 50V, 104 links SC= RK50MO or DID 50V, 106 links

MODEL IDENTIFICATION:

YEAR MODEL PRODUCT CODE FRAME / VID ENGINE
1979 CB650 426 RC03-2002472 - RC03E-2002518 -
1980 CB650 460 RC05-2100002 - RC03E-2100009 -
1980 CB650C 460 RC05-2100008 - RC03E-2100011 -
1981 CB650 460 JH2RC0507BM200013 - RC03E-2200004 -
1981 CB650C 460 JH2RC0518BM100009 - RC03E-2200004 -
1982 CB650 460 JH2RC0509CM300003 - RC03E-2300001 -
1982 CB650SC 460 JH2RC0808CM000013 - RC08E-2000018 -

CYLINDER HEAD IDENTIFICATION:

O.K, this is kind of tricky. Evidently there are in fact two different cylinder heads used on the 650. I can't imagine why, I never thought this was true until I looked up the part numbers. I'm guessing that they did it to better accomidate the CV style carbs, although you'd think they would have just molded new rubber manifold insulators? Why Honda would go through the trouble and cost to recast the head is beyond me, but maybe there are other differences. I'm assuming that the reason the '82 nighthawk casting has a unique part number is because it was painted black, and is in fact the same version as the '81 and up silver heads were. Please help me fill in the blanks below so we all know what's going on.

HONDA PART # CASTING #
1980 CB650 12200-426-020 ?
1980 CB650C 12200-426-020 ?
1981 CB650 12200-460-771 ?
1981 CB650C 12200-460-771 1112/23
1982 CB650 12200-460-771 ?
1982 CB650SC 12200-460-780 ?

CARBURETOR IDENTIFICATION:

Custom and Nighthawk specifications are the same as the Standard Model unless otherwise indicated by a C=(Custom) or SC=(Nighthawk). I believe the U.K. models at one time used the VB54 carbs, info on this would be appreciated.

1979 1980 1981 1982
TYPE: Piston Valve, 26mm Piston Valve, 26mm VB VB
ID NUMBER PD50A PD50B VB 44A VB 44A, SC=VB 44C
MAIN JET #92 #92 #120 #120, SC= #118
MAIN AIR JET ? ? #100 #100, SC= #80


Mechanical (Piston Valve)

Constant Velocity (VB)

TIRE SIZE IDENTIFICATION:

1979-1982
Model: Standard Custom & Nighthawk
Front: 3.50H19 (4PR) 3.50S19-4PR
Rear: 4.50H17 (4PR) 130/90-16 x 67S