still not starting

[rhyatt]

Did you manage to realign the 2 contact points after cleaning them.

[Barnsey]

Yes the points are looking good, well aligned and I set the gap to 15 thou.  The original condenser is back in now. 

  BTW I added extra ground wires from the engine and the headlight to the grounding point on the frame, so return path resistance shouldn't be an issue. 

  Are we at the point of replacing the coil?  Not that I have any direct evidence that there is anything wrong with it.  Is that a more modern improved version available? 

[rhyatt]

I think you said you'd changed the loom.just to prove the ignition side.
Disconnect the battery side of the ht coil , in other words separate the coil from the bike.
Then run a hot wire from the negative battery straight to the coil.
The cb side of the coil goes via the points to earth.
Now kick it , does it spark a strong blue spark , does it run ?

Remove neg wire to turn it off

[Steve.S]

Assuming you really do have a 2mm spark, as I said before, this is no good at all. It should jump 5/16" which could be about 8mm, but I don't know. They didn't use foreign measurements when I was at school.
As Rhyatt has suggested, make a direct feed to the coil from the battery, but this was suggested many moons ago. I hope you have done it by now!
If you like, you could remove the coil, connect a battery to it and test the spark on the bench, by repeatedly touching the live wire on the coil terminal. It should spark every time you remove the feed wire.
If you're not sure about your spark plug tester, I have heard that you can get 2 old spark plugs, break off the earth terminals, fit them opposite each other at 90 degrees to the vice jaws with cable ties and with all the electrical connections connected, wind the vice in and out to establish the exact gap. But this might be overkill.
A 1/4" gap will indicate the coil is producing 10,000 volts and 5/16" will indicate 15,000 volts, which should be enough to start your machine.
If it were me, I would simply purchase a new coil, and send it back if it makes no difference. Then you will know if the coil is OK or not, irrespective of any resistance readings.
Have you tried hitting the coil with a hammer? I quite often find this works wonders with lots of things.

[Barnsey]

I'll try adding a direct wire from the battery to the coil today, but I am not expecting too much from that.  The path through the switch and ammeter really is only a couple of ohms.  Also this is all stuff I have done before.  I wonder if I should have started a new thread in the forum as I went through all of these tests to get it working the first time and then, after a couple of months laid up it gave up again. 

  I have a new, non-resistor type cap on order and I am hopeful that will help.

  The idea of setting up two plugs on a vice is a good one. I have seen this done on television. although I don't have a pile of old plugs sitting around to use, so , probably just as well to order a new coil if it comes to it.  Can anyone recommend a 6V coil other than Lucas?  I am going off of Lucas as the quality is what might be called 'variable'. 

  Expect an update later today. 

[Barnsey]

Adding a wire directly from battery negative to the coil didn't achieve much in terms of spark strength. It was much the same. 

  I double checked the timing, and, yes, it was set up to spark at the end of the exhaust stroke.  This completely baffles me as it was running and I hadn't altered the timing. 

  Anyhow I set up the timing on the compression stroke with both valves closed.  And then I switched on and gave it a kick. 

    It initially looked positive as it kicked back on me just as I was starting my kick.  It didn't hurt thankfully.   But I thought I was onto something.  However I kicked it a few more times and not so much as a chuff.  It looks like I will be waiting for that spark cap to arrive. 
 

[rhyatt]

If you've bypassed everything and still have a weak spark
You've cleaned and aligned the points and exchanged the conder with no improvement in spark strength.
Then a new ht coil is the only thing left frankly.
Lucas /wassell 6v coils are about 20 quid  give or take.
I use Chas bikes and Kidderminster motor cycles as reliable parts people

[Steve.S]

Sorry I was asking you to repeat work. I wasn't clear you had previously fed the coil direct.
Anyhow, good, you now know that the feed from the switch is OK.
You could get a Bosch coil from Tanya.
As I said before, kicking back is usually caused by over advanced ignition timing.
Form what you have said, your ignition timing is moving all over the place, so it is worth checking it repeatedly in the way I described, after you have kicked the engine over a few times. It shouldn't take long.
If it does keep altering, then I would remove the "distributor" and examine the gears and drive train (or whatever the C15 has.) Maybe the drive is slipping somehow?
However, with a 2mm spark I doubt if it will ever start.
Always remember to only do one thing at a time. If you do 5 things and it starts, you will not know which of the 5 things was the problem.
Chin up, keep at it. You'll soon have it started and be able to give it a damned good thrashing.

[Barnsey]

I don't think the ignition timing is moving by very much.  It is just a question of setting it up on the right stroke.  I am still bothered that the engine ran with the points breaker 180 deg out.  I have a photo of the bike early on in the job and I can clearly see the distributor in that position. 

  Anyhow, the new Lucas coil and non resistor cap are on order.  Next weekend I will be on holiday, but only for a couple of days, so expect a bit of a gap before you hear from me again.  I can just tell that I will be on hols with my family and itching to get on with the bike.  That is what usually happens. 



   

[iansoady]

If it ran with the "distributor" 180 degrees out it suggests you're now trying to time it on the wrong stroke. Very easily done.

[Barnsey]

That's what I thought, but the instructions in the manual said to set it with both valves closed, which they would be at the start of the power stroke.  I removed the valve covers and both rockers rattled loose. If it was the start of the induction stroke, the inlet valve would be open (i.e. not rattly). SO  I am sure it is correct.....  That is unless anyone can suggest otherwise?   

[rhyatt]

if you were on the stroke with the valves closed , then you needed to continue upwards with your spoke or whatever down the plug hole and the engine in 4th gear and on the stand gently nudging it upwards to TDC then back a whisker and the points should have JUST begun to open.
the handbook says .007" which is just about the same as the inlet valve clearance gap ie barely anything BTDC

[Barnsey]

The Lucas coil arrived today but it is a different size to the old one!  DOH! 

48mm vs 40mm in diameter.  I'll give it a try, while I have it, and then I might be looking for a clamp bracket for it.   Can anyone recommend a clamp which will fit both bike and coil without costing a pile of cash? They seem to sell for crazy money considering what they are. 

[scifi]

Getting back to the cam and valve opening discussion.   On the non power stroke at TDC, the valves will have an overlap, where they are both open a small amount. 

Racing cams have a large overlap of maybe 50 degrees each.  Road bikes have much less overlap, and lawnmower and industrial stationary engines have zero overlap.

The position where both valves are open the same amount is -nearly- always at TDC. and is a good way to check your cam timing.

[rhyatt]

Kidderminster motor cycle
01562 66679
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