re-newing HT leads

[Johnwebley]

as my CB500/4 K1 is approaching its 40th anniversary,

it has come to my notice the HT are hard and brittle ,

especially when cold,

when riding in wet weather ,I am getting problems of cylinders 2,and 3 shorting out,

so I would like to renew,and extend the HT leads with nice new flexible leads,

could I have your suggestions on the best/easiest methods ?

[LesterPiglet]

You can get a splice kit but I made my own.


Cut your old lead and screw in a self tapper, cut off the head. Screw the new lead on. Put some silicone inside a piece of tube and slip it over the joint.

[Bitsa (Ralph Wright - RIP)]

Lester.
That will do it it but I would use black shrink down sleeving to make it look the biz
Cheers
Bitsa

[LesterPiglet]

You'll never see it/them.

[Bitsa (Ralph Wright - RIP)]

True,
But I would know
Cheers
Bitsa

[LesterPiglet]

  Does shrinktubing harden? That's still flexible after 30+ years.

[Bitsa (Ralph Wright - RIP)]

Lester good point,
I replaced mine with the real thing but one thing I have noticed rock hard when cold and so supple when warm.So whats the answer?Go with what your happy with is my view and if no problems stay with it.
Cheers
Bitsa

[hairygit]

Are you sure it's the ht leads? Reason I ask is it is very unusual for 2 cylinders to have dodgy ht leads, the fact it's always no 2 and 3 that mess around I'd be checking the low tension side, all the wiring and connectors from the points to the coils, especially the bullet connectors, you'd be amazed how much crud can form in them, and pay particular attention to the join in the wires by the back brakelight switch, another common problem area. If the bolts holding the coils to the frame appear rusty, clean them, better still replace them

[florence]

I've never tried this on 500 coils so I don't know whether it is the same but on my CB350K the HT leads seem to be held in with resin.  I put the lead in the vice and pulled really hard on the coil and the lead came out leaving a spike inside the coil.  I was then able to push in a new lead and then seal with glue.  This has worked well for the last twenty years. 

Does anyone else know if this works with the 500 coils?  I have a spare set but I'm reluctant to try it as these bits are not as easy to get as they were twenty years ago.  I didn't mind taking a chance in the past when bits were cheap and plentiful.

Incidently, my 500 also is dreadful in the rain, it goes down onto two cylinders as you describe; I tried smothering the coils in silicon grease but not much better.  It usually takes about five miles in the wet for the engine heat to dry everything out sufficiently well to allow proper operation.

However, the bike is better behaved since I started keeping it under a tarpaulin.

[Johnwebley]

thanks all for your help,

in reply to Hairgit,over the years as the lead hardened ,they become more and more difficult to detach from both inner plugs,and the
cap fixing became worse over time,removing the damaged lead end,to give the cap fresh to bite on,has now made them very short!

the above is also the reason I had same problems as Florence ,

the water runs down each lead into the cap,and shorts out,
the outer plug dont have the same problem,

[peterengland]

my bikes runs like a piece of junk if the rain is on the leads, when I bend them they are cracked etc letting in water, can't I just coat/spray them with something to keep the water out?

[LesterPiglet]

I tried that. Nothing worked. I think the leads just break down with age.

[AshimotoK0]

On the 750 the internal core often fatigues and breaks at the point of entry into the coil. A few years ago I investigated cutting away the plastic moulding of the HT coil body and found the HT lead is terminated internally to the coil HT secondary with solder onto a brass termination. You can then solder a brand new piece of HT cable to the termination and then remould over with black epoxy putty to seal again and when cured you can file/sand to original profile. This was on CB750K0 coil. My garage is in a right state at the 'mo cos I have an MG Midget languishing  in there, which I need to get shut of,  but once I find the coil I fixed I could tell you the approx. position of the brass internal termination. The rubber outer sleeve was hard to find though as it's very thin walled. Not sure about 500/4 coils but guess they could be similar.

Cheers ...... Ash D

[matthewmosse]

I have 2 sets of coils somewhere that have been the subject of this kind of attempted repair, neither worked sufficiently reliable though they were removed more in the remove suspect items and replace to eliminate suspect faults rather that know to be the fault. Inside the insulation I've found a copper spike - if I were to attempt my own repair I would solder to this, rather than rely as the people who did mine, on trying to just push the new ht lead into/ onto the spike and seal with araldite - I'm pretty sure from the green fur found on the ht lead and copper splike that damp got in there within 6 months. I found the ht lead off a roll in a local garden machinery repair shop was really nice and thin but subttle - noticed this on a few stationary engines that I have owned which have had new ht leads. seems to work. I have had to replace a few ht leds due to cracking in the insulation letting them short out in the damp, I was lucky with my 500/4 - it had brand new coils just before I bought it., never had it shorting out due to rain, or my 550 before that, though they did have a reputation for it.