Connectors - The 3.9mm bullet connectors on this bike are smaller than 4.7mm standard European types. Available from Vehicle wiring products.
Headlight - The original Stanley tungsten headlight 12Volt 50/35W can be up rated to a Cibe quartz halogen 12V 60/55W P43T H4 unit, a modification carried out by numerous owners in the 70's. This is a tight fit and lots of jiggling with the wiring is needed. A H4 quartz halogen P43T 35/35W lamp is available if you want to put less stress on your ageing electrics and is ideal as a daylight riding light.
Horn - The original equipment is far from adequate on today's roads. I recommend upgrading to a modern 105dB or greater, some nice chrome examples are available.
Repairing HT coil leads - This can be done by first cutting away the old rigid PVC leads to within 15mm of the coil. Use copper cored, i.e. not suppressed, 7mm silicone HT lead (very flexible) covered with 6mm neoprene sleeving. This is a swine to slide on, use of a lubricant (Hellerine oil) will help. When covered roll back on itself about 10mm of the sleeving for use later to cover the joint. Use a 1 inch long self tapping screw of suitable size with the head cut off and that end sharpened to a point. Screw in 1/2" to the existing wire and then screw the new HT lead in to the 1/2" thread that remains exposed. Seal the joint with silicone rubber compound and roll the sleeving forward to cover. Further waterproofing to the coil cable outlet is advisable using more silicone rubber solution. You should now have better than new water tight coils.
If broken near the coil housing the plastic can be removed carefully with a Dremel till the brass pin is exposed. A new length of cable can then be pushed home and epoxy into place.
A better alternative is to try and find coils with a removable HT lead from another bike at your local breakers yard. CBX550, VF750 and some Kawasaki's of the era have the same spacing for the fixing screws. This allows us to use the CB400F's aluminium brackets for easy mounting. Originally intended for electronic ignition, may cause premature contact point failure due to the higher current.
Testing HT coils- From lead to lead (1 to 4 and 2 to 3), including suppressor caps, will read approx. 25K ohms and the input to each coil around 5 ohms. Coil 1 & 4 is bolted to the right hand side of the frame with 2 & 3 on the left. The length of the leads is approx. 1 = 530mm, 2 = 150mm, 3 = 230mm, 4 = 230mm
Testing condensers- Using a multimeter on the capacitance scale these should measure 220nF or 0.22uF. The pattern type I fitted went open circuit within ten miles resulting in a 30MPH ride home coughing and spluttering!
Suppressor caps 1&4 = NGK VD05F, 2&3 = NGK XD05F
Spark plugs = Class 2 NGK D8EA 12mm fine pitch, 19mm reach, temperature 8 (mid). DR8EIX are the iridium type. Denso standard plug is X24ES or IX24 iridium type. The new Iridium spark plugs give longer life, better starting and smoother running?, but, at a cost of around £7.50 per plug, not cheap. Try A.R.E. for these. The NGK iridium type have an internal resistor of 5K built in and may give problems?, people report poor fuel consumption. My first impression is less lumpy at low RPM's allowing better drive from a standing start. Full conclusions follow in Autumn 2004.
Rear Light on bikes of this era have only one lamp and should it fail then your rear end is left in darkness....very un nerving. Modern bikes are now being fitted with LED rear lights that have much longer life expectancy. Replacement 12 LED BA15D lamps are available from M&P etc. but are strictly not legal for road use in the UK, if you do fit them always use an LED of the same colour as the lens of the light i.e. red.