Startup after rain.

[Bob_Roller]

Ok, just checking....its this coil I want, the Green DC6-1 with dual outputs and 3.0ohms primary resistance? If so, thats only £62.33p!
www.dynatek.com/sports_bikes_ignition_coils.html

Bad link to the coil site .

If you have the contact breaker type ignition, you need the 'green' 3 ohm coil .

When I ordered a Dyna 'brown' coil for the '84 LS about 6 weeks ago, I asked Rick Jones, the owner of Motorrad Elektrik, what kind of service life to expect from a Dyna coil .

The response I got was 20+ years, he has had only 2 or 3 coils sent back to him, that had actually failed .

[Barry]

Yes DC6-1 green is the right one

Couldn't get your link to work did you mean this one
http://www.dynatekuk.com/sport_bikes_ignition_coils.html

[Barry]

If your twin 6v coils are original then after 30 years they probably need replacing (mine too when I get around to it) and Dyna coils are highly regarded. Just a thought though...

Looking back over this thread I noticed no one mentioned the condenser as a possible cause of your weak spark. Condensers are notoriously difficult to test except by substitution.  One indicator of a faulty condenser is excessive sparking at the points or you could disconnect it and see if there is any difference in the spark strength. Disconnection is actually quite difficult come to think of it because the connection to the points is shared with the condenser so you would have to do a temporary bodge somehow to test it that way

[Bob_Roller]

I'd completely forgotten about a faulty condenser, as I haven't worked on a vehicle with points type ignition, since 1981 ('79 Yamaha XS400) !!!!!

From what little I remember about the system, won't a faulty condenser, leave the points a bit blackened, or 'sooty' looking as well ?

[Barry]

Come to think of it Bob until I got an airhead 3 years ago I'd forgotten about points too.  I bought a new Suzuki in 1982 and rode it for 14 years without once even thinking about the ignition timing let alone adjusting it.

Yes I think a failing condenser would cause the points to burn from excessive arcing. There is a theory that with a perfectly matched condenser both points contacts will wear evenly.  In the real world they always seem to develop a pip on one side or the other.

The other failure mode for the condenser would be for it to short out in which case the ignition would produce no spark at all.

[nhmaf]

Yes, I agree with Barry - a faulty condensor can cause oddly worn/burnt points surfaces, or if it fails shorted, no spark at all.   Given the usual failure rate of the original coils on these bikes, we do tend to always go there first.   IT has been a long time since I've had to deal with any points too (though I hope to get back into it with a 1970s vintage airhead soon-ish) I used to replace the condensor with the points as a matter of habit - no sense in trying to pinch pennies when a bad condensor can ruin a new set of points and/or cause all sorts of hardships on the roadside.

[montmil]

Bad condensors leave the point's contact pads with little "spikes" built up as metal is transfered from on contact to the other.

Monte

[BooG]

Loads of great advice! Will be at work this weekend (as long as all the parts make it through the postal disruption!?), so I'll take some photos and let y'all know how I get on!

[BooG]

So..bad weather has held me back somewhat..but finally I have managed to hook up all the bits! Dyna coil is on rear bracket. Its a different configuration to the ones I have seen. The intergral epoxy bracket was pre drilled with two holes (presumably for a Harley). I put another one next to the rear one to mount it. The wires have been extended (soldered/heat shrinked) along with ring type adapters to replace the old spade type. New HT leads and caps/plugs. A new set of points. They didn't actually look to bad, but I'm gonna stick another condenser in anyway as I have one. Battery earth cable remains in the same position as it was. There was a brown wire earthed to the front coil bracket. I have left it there. Not on schematic, so I was wondering...?  Will go for the start up on Monday. Fingers crossed!

[Bob_Roller]

That brown wire on the forward coil bracket, is a main ground, or earthing point for the electrical system .

It's a common problem, to have the metal bracket crack, and give all sorts of odd electrical problems .

Check it for cracks, while you've got it apart .

[Rob Valdez 79 R65]

It's a common problem, to have the metal bracket crack, and give all sorts of odd electrical problems .
 

This is the 1978-1980 models Bob refers to.

And on mine, when the mount broke, taking the front coil and the main ground with it, the bike died (due to the lack of ground).

I drilled a hole in the connector plate, and made my new ground point, there.  (don't be shy with the dielectric grease)
The coil is held on with a couple of really big hose clamps, these days.

[BooG]

Here it is so far! Belting down with rain at mo so no chance of a start up for the next hour or so.

[Barry]

I've never noticed a main earth connection on my front coil bracket. Maybe a PO moved it some place else. I'll have to check.

Is it only the front coil mount that fails and is it the coil bracket itself(can't see how it would) or the lug welded to the frame top tube ? in which case my ignition would die as I've used the rear coil bracket mount to earth my ignition amplifier. Maybe I should move that someplace else too.  

[Rob Valdez 79 R65]

It was generally the front coil bracket that would break off of the frame tube at the welds.
I think I have heard of the rear breaking also, but mine is fine.

Here is a good thread on auxiliary grounding on Boxerworks.
http://boxerworks.com/phorum5/read.php?6,43277,43277#msg-43277

[Barry]

That's a thought provoking thread - thanks Rob.

As a life long exponent of ohms law I should probably pay more attention to the efficiency of the wiring.

For me Duane hits close to the mark with his comment about not necessarily relying on measurements with an ohm meter. Having a good earth helps to achieve very low voltage drops in a circuit and that's what matters. Rather than measuring resistance the correct thing to do is to measure voltage drop under actual working conditions, then you get to see what's really happening. Positive supply cables are just as important too. Its the total voltage drop in a circuit that counts. Ask anyone who has grappled with 6 Volt bike electrics where these issues are twice as important.