Spark plug lead gone bad, what do?

**Blackshear** · 15th September 2009, 19:19

Afternoon, gents.
I played sponge with my bike yesterday, giving it a decent outer clean.
Went to fire it up and ride my sparkling beast around the block.
That noise, it's only running on 3 cylinders.
So I figure it's just a lead with a bit of water being all cool and wet, and let it sit overnight.

Still doesn't run. Off goes the tank, and it's immediately apparent as to WHY.

So I tried screwing it back in after cleaning it, nothing.
Do I just need a new lead or whut?
How much does a foot cost, if so?

**Henk** · 15th September 2009, 21:37

If the lead unscrews from the coil, cheap as from repco or your local auto sparky. If not you may be looking at a new coil if you can't shorten it.

**F5 Dave** · 16th September 2009, 10:15

Just beware that car silicone typre coil wire isn't suitable, you need the copper core stuff. So you found the lead had come off the cap huh?

Try trimming back the lead until you see wire & then screw it back in. Then you could measure between both caps with a multimeter on ohms (~$10-$20 for a meter from Dick Smith & worth owning one, you will learn to drive it).

Each cap should have resistance of ~5kohms, maybe up to say 8 on std suzi stuff, so you'd expect to see maybe 16kohms between the leads depending on the coil. If you're seeing more measure the caps & coil separately.

More than likely having the lead off for a while has fouled the plug & it needs replacing or if lucky could clean under a gas torch.

**Subike** · 16th September 2009, 10:20

I recently got 1 meter of coper cored lead from a local sparky for $5.

**CookMySock** · 16th September 2009, 10:45

Originally Posted by F5 Dave

clean under a gas torch.

I have done this and it works well, but be careful that you dont overheat it as I had one go BOOF and blow its guts out all over the floor. Fucked if I know why a sparkplug might do that, but I was fortunate not to get VERY hot shit sprayed in my eyes.

Wear safety glasses at least, please.

Steve

**F5 Dave** · 16th September 2009, 10:51

eek. I guess you found the temperature that the porcelain could cope with, it's localise temp probably doesn't get that hot for that long. I was just using a propane torch, not sure how hot that gets.

**CookMySock** · 16th September 2009, 11:36

Originally Posted by F5 Dave

eek. I guess you found the temperature that the porcelain could cope with, it's localise temp probably doesn't get that hot for that long. I was just using a propane torch, not sure how hot that gets.

Oh this was an ordinary venturi propane/air heating torch, not an oxy-propane set. I just heated hell outa the fucker, for fun mostly.. as ya do.

Steve

**vifferman** · 16th September 2009, 12:54

Originally Posted by DangerousBastard

Oh this was an ordinary venturi propane/air heating torch, not an oxy-propane set. I just heated hell outa the fucker, for fun mostly.. as ya do.

I'd imagine the metal bits expanded more than the brittle porcelain could cope with.

**Blackshear** · 16th September 2009, 15:17

Cheers for the prompt replies, gents, much taken aback after looking at the few 'active' threads here.

I would cut back the lead, but doing so would be silly. There is literally only enough lead there to get from the thingy, to the cap. I'm going to call supercheap/repco and see what they have stocked.

I took her out just for a little test ride after ramming the lead up the caps ass as much I could, and it was sad. Full/no throttle would yield the dull sound of a missing cylinder, but 'coasting' throttle would produce sad little random spurts of full power. Poor girl

Are copper-cored leads generic, or is there a vast range of resistance out there?

EDIT: After calling cycletreads, they have been priced at $18 per lead, for a specific-to-my-bike lead.
I guess after 20 years, the original ones had a pretty good life.

**vifferman** · 16th September 2009, 15:41

Originally Posted by Blackshear

Are copper-cored leads generic, or is there a vast range of resistance out there?

Copper leads have very little resistance - that comes from the caps. All you really want is summat the same diameter, with a decent core for the spikey thing to connect to - everything else is kinda immaterial.

**Blackshear** · 18th September 2009, 12:09

The $18 was for a spark plug

Time to ring around the other bike shops and see if they have what I want!

**Ixion** · 18th September 2009, 12:16

OEM HT leads (cars certainly, bikes maybe) often are not copper cored. The electrical conducting core consists of black string. A penny saved etc I guess.

You can buy proper HT cable from Supercheap. You may also be able to buy from them (failing that, any good auto sparky) a HT cable joiner. Basically a bit of plastic with a spikey at each end. Useful if you have one of those damn "moulded direct into the coil" leads.

**Blackshear** · 18th September 2009, 18:07

Originally Posted by Ixion

OEM HT leads (cars certainly, bikes maybe) often are not copper cored. The electrical conducting core consists of black string. A penny saved etc I guess.

You can buy proper HT cable from Supercheap. You may also be able to buy from them (failing that, any good auto sparky) a HT cable joiner. Basically a bit of plastic with a spikey at each end. Useful if you have one of those damn "moulded direct into the coil" leads.

Ja I gave supercheap a call and they were all 'yeah lol, wut r u tlkin boot?', so left a message at the old neighbours residence. Not sure if he still works as a sparky or not since he was laid off a few months ago.
Either way, no point fixing it until I get my exhaust tip bracket re-welded.

I may as well re-do all of them while I have an abundance of spare time, cost notwithstanding.

**batboy** · 18th September 2009, 21:46

Are u sure is a crimp type fitting? if its a screw type just screw it back in? but shine a light up the end and check

**jonbuoy** · 18th September 2009, 22:07

Originally Posted by Ixion

OEM HT leads (cars certainly, bikes maybe) often are not copper cored. The electrical conducting core consists of black string. A penny saved etc I guess.

You can buy proper HT cable from Supercheap. You may also be able to buy from them (failing that, any good auto sparky) a HT cable joiner. Basically a bit of plastic with a spikey at each end. Useful if you have one of those damn "moulded direct into the coil" leads.

I think that's a resistive lead - no need for resistors in the plug caps with that type.