No Spark

[Barnsey]

Right!  Having found neutral,  I have kicked the bike over, but no start

Since the engine last ran I have fitted a new loom, but the engine hasn't been opened, so the timing should all be good. 

The three wires going down to the points are correctly connected, I checked. 

The battery is charged and the lights all work. 

The carburettor is filling with fuel and isn't leaking now.

I asked my wife to prod the kick starter and there is no spark on the plug, although she din't really kick it with any serious welly. 

  This could turn into a bit of an investigation but does anyone have any bright ideas before I   start?   

  BR,  Ian

[Derek996]

I'm not familiar with e C15 wiring but I'd start by checking for power at the coil. Easiest to use at test lamp connected between a good ground point and the negative side of the coil. Th bulb should light up when the ignition switched on. When the test lamp is connoted to the other (+ve) side of the coil it will light up when the points are open but less brightly. If you get these results then there should be sparks unless the coil is faulty.

[neil1964]

How long since it last ran?
Is your battery fully charged, ignition switch making contact (if you have a dc voltmeter meter check that you have voltage on the low tension feed from the ignition switch ie - lucar connectors on the coil)
Check you have a spark plug of correct type (preferably new) gapped to 25thou (0.6 to 0.7mm)
Check the connections of the HT lead (thick black wire between plug cap and coil.  You can remove the plug cap and strip 1/4" of insulation back and see if there is a spark between the copper inner wire and the cylinder head when you spin it over (easier with plug out!).
Are the contact breaker points clean of oil/cack/corrosion and set to correct gap (I'm guessing 12-15thou (0.3-0.4mm if you only have metric feelers)
Presumably you know you have a proper fuel supply (and I mean new fresh stuff, not what has been sitting in tank for weeks/months/years?) there because the plug is wet (but not flooded or a fouled plug).
Have you cleaned the carburettor for blocked filters and pilot jets (use carb cleaner and compressed air, not bits of wire, to check)?
All part of basic check list

[neil1964]

Sorry Derek, posts crosseed.
I think bike electrics is your 'thing' so I'll leave you to it now!

[Barnsey]

Thanks for you input everyone. 

  I have no volts on the coil, so that seems pretty fundamental ahead of everything else.

  For diagnostics I am running the electrics from a bench PSU, so no issues with flat batteries, although I'll connect up the battery again when I next try to start it. 

  Looking at the circuit diagrams, the ignition looks to be routed through the lighting switch.  Do the lights need to be switched on to start the engine? 

   Colour coding is confusing.  I have two circuit diagrams, and the glossy diagram which came with the Lucas loom.  All three have different colours. 

        BR,

          Ian

[rhyatt]

Just to try and get it running , you could create a separate circuit for the spark.
1 wire from points to + of coil
Neg of coil give that a 6v supply
Now kick it over to check spark and if so , try starting it

[Barnsey]

Yep.  I am spending an age looking at the circuit diagrams. 

 It looks like the negative supply goes through the ammeter and the ignition switch to the white on the coil.   
Black and white on the coil goes back through the iginition switch to the centre pin on the alternator.  SO there isn't much which could be at fault. 

 

[rhyatt]

At this stage of things, I'd be tempted to rig up this totally separate wire to get it sparking and running.
Wouldn't even worry about charging.
Just let it run , see what noises it makes , gears select etc.

[scifi]

The C15 that I had over 40 years ago had Energy Transfer Ignition, so no battery, just the points opening at the peak of the a.c. electricity from the generator.   (Maybe this was because it was a trials version..?)   If yours has a battery, then you should get 3 amps through the coil just prior to the points opening, then this current goes to zero when the points open, just before tdc.   Your ammeter can be wired to show this current, and it gives a good indication of when your are kicking over tdc.  Both my R.E. Bullet, and BSA C11, have an ammeter that shows the coil current, as well as the battery charge current when the engine is running.

[neil1964]

I agree with rhyatt.

Get it running with total loss system first as proof of concept.

Can you post details of your bike and a link to the wiring diagrams that you are using?