CB650SC/Specifications

Type	Standard
Frame	RC13 (shared with CBX650E)
Displacement	655 cc
Power	72 bhp @ 9500 rpm
Dry Weight	197.0 kg (434.4 lbs)
Top Speed	233.4 km/h (145.0 mph)
1/4 Mile	12.13 s @ 174.50 km/h (108.43 mph)
Wheelbase	1,461 mm (57.5 in)
Seat Height	790 mm (31.1 in)

Common Threads and Sizes

Item	Size	# needed	Note
Engine Oil Drain (sump) bolt	M12x1.5mm	1
Short hydralic banjo bolt	M10x1.25mm	6	Brakes and clutch
Double hydralic banjo bolt	M10x1.25mm	1	Brakes

Engine

Oil

Weight	Grade	w/ filter	w/o filter
SAE 10W40	API SE-SF	2.5L	2.2L

Ignition System

Timing

The engine speed is sampled directly from the crankshaft by two pickup coils placed at Cyls. No. 1&3 TDC and Cyls. No. 2&4 TDC. The two "pickups" are VR(Variable Reluctance) type, and together are referred to as the "Pulse Generator" in Honda literature of vintage. Each pickup is a coil of wire, wrapped around a steel core. One end of the steel core is exposed to the outside of the rubber moulded casing of the pickup, toward a sheet of steel attached to the crankshaft. The other side of the steel core is a magnet with the north pole pressed against the steel core and the south pole facing away from the entire assembly. Each pickup has a coil of wire with a resistance of 330ohm +/-10%.

As the crankshaft turns the stamped steel bolted to it approaches, aligns with, then passes the steel core of each pickup. This induces reluctance, and a voltage dip and spike into the coil. At low RPM the crankshaft position is detected at a low frequency AND low voltage. The frequency is of course directly correlated to the engine speed, velocity, or RPM. The voltage is proportional, starting as low as tens of Volts up to hundreds of Volts at high engine RPM.

From what I have read, using two sensors is very important to preventing the engine from running in reverse, as the controller can detect which pickup is triggered first.

Control

The Ignition Controller is a TCI(Transistor Controlled Ignition) type. It is referred to as the IC(Ignitor Controller) in Nippondenso and Honda vintage.

1. Condition VR signal input from the Pulse Generator
2. Calculate Engine velocity and position
3. Calculate ignition advance (see Advance table) from velocity
4. Calculate ignition offset from position and ignition advance
5. Trigger appropriate coil's charge duration (dwell?) and ignition event

Advance Table

RPM	Degrees Advance
At idle min-1	10 BTDC
Full advance/min-1	32 BTDC/3000

CB650SC D-F(83-85) CDI Pinout (Module side)

	Pulse gen/pickup coils plug				Ign. Coils Plug
	3	2	1		2	1
3-2 Pickup ->	NP	Y	W	+	B/W	L	4-1 Ignition coil	12v signal
4-1 Pickup ->	NP	L	W	-	Dg	Y	3-2 Ignition coil
	6	5	4		4	3	Tees off to tachometer signal

Ignition

• Ignition coil primary resistance: 2.8 ohms
• Ignition coil secondary resistance: 13.6-15.5 ohms
• " with spark plug cap: 21-28k ohms
• Spark plug resistance: ohms
• Spark plug gap: 0.8-0.9mm (0.031-0.035in)

Carbs

Keihin VE54A

Item	Spec	Note
Venturi	29.2mm (1.15in)
Type	VE
Style	CV	(constant velocity)
Float	18.5mm +/-1mm (0.61in +/-0.04in)	Non-adjustable
Idle	1,100RPM +/-100RPM
Throttle grip free-play	2-6mm (0.08-0.24in)
Fast Idle	3,000RPM +/-500RPM	choke on
Needle marking	"79K"
Choke type	By-starter

O-rings

Desc.	Part Number	I.D.	Thickness	Number
Small, (fuel tubes)		6mm	1.8mm	4x
Large, (fuel tee)		7mm	2mm	2x
Thin, (breather tube tees)				4x
Cly. head to boot couplings	91306-ME5-003 -> 91306-HA0-003	33.7mm	2.6mm	8x

Carb Parts

• Keyster kit (N.A.): K-893HK (http://www.siriusconinc.com/products/detail/2685)
• Keyster kit (E.U.): KH-1195N (https://www.3pracing.com/en/keyster-carburetor-rebuild-kit-kh-1195n-for-honda-cbx-650-1983-1985.html)

Part/Jet	Size	OEM P/N	Keyster P/N	Series	Length	Diameter (thread)	Diameter (head)
Main	#115	99101-393-1150 -> 99101-GHB-1150 -> 99101-MAZ-1150	KHM-110115	99101-393 or KR28	8mm	4.9mm	6mm
Slow	#35	99103-MA4-0350 -> 99103-GY6-0350	KHS-29C035	N424-21(N424/21) or K26	28mm	5.9mm	4.9mm
Needle Holder		16165-449-771
Needle Set (Canada)	79K	16012-ME5-621 -> 16012-ME5-671
Needle Set (Europe)	79P (#D476)	16012-ME5-611	KHD-0476Z
Needle Set (CB700SC/700S)	2SK
Idle Screw Set		16016-ME5-671 -> 16016-KR3-671 -> 16016-MY6-770
Idle Screw Set (Europe)		16016-MA6-003	KHSS-138
Float valve		16165-413-751	KVN-16N00
Needle Shims					ID: 3.2mm	OD: 7mm	thickness: 0.5mm

Stage	Main	Slow	Needle shims 0.5mm (per each carb)	Note
0 (OEM)	#115	#35	0	Stock
1	#118	#35	1	stock engine and with stock air intake and stock exhaust system
2	#120	#38	1	stock or lightly modified engine with improved air intake using stock air intake box and baffled aftermarket exhaust or lightly modified exhaust
3	#125	#38	2	stock or lightly modified engines with individual air intakes and baffled aftermarket exhaust system
4	#125	#40	2	modified engines with individual air intakes and non-baffled exhaust system (racing use only)
5	#130	#40	2
Pro	#118, #120, #122, #125 and #128	#38, #40	2	experimenting with different engine, air intake and exhaust system

Exhaust

Sealing

• Graphite coupler seal x1 - 18392-MG7-750 - 42.8 x 48.6 x 20mm
• Copper crush rings x4 - - 43.2 x 34.8 x 4.2mm

Wheels

Construction: Cast Alloy

Tires

Position	Size
Front	100/90-19 (OEM: 3.50-19)
Rear	130/90-16

Brakes

Position	Type	Number	Size
Front	Disc	x2
Rear	Drum	x1

Suspension

Forks (Front)

• Showa
• Diameter: 39mm
• Type: leading-axle
• Adjust: air-adjustable
• Bushings: dual Syntallic
• Anti-dive: TRAC

Shocks (Rear)

• VHD
• Type: rebound damping
• Adjustable: four-way