Author Topic: #1 Plug cap shocking the H**L outta me  (Read 1688 times)

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Offline Gene

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#1 Plug cap shocking the H**L outta me
« on: September 29, 2015, 11:32:17 AM »
1975 CB550K - If I touch the #1 plug cap with the bike running - shock!  Found this out by accident.  No problem with the other three.  I read that these "burn out" after a while and the spark can jump to the head/frame/your leg etc.  I'm assuming that's what this is?  Either way, a replacement is on the way - just curious. I never trimmed the wires, and these are probably the original plug caps - I never changed them out.

*1973 CB750K3 (Bow)

Offline MickB

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Re: #1 Plug cap shocking the H**L outta me
« Reply #1 on: September 29, 2015, 11:36:22 AM »
Replace the lead and cap

Offline flybox1

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Re: #1 Plug cap shocking the H**L outta me
« Reply #2 on: September 29, 2015, 12:05:49 PM »
replace them all. . .
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline Gene

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Re: #1 Plug cap shocking the H**L outta me
« Reply #3 on: September 29, 2015, 02:46:43 PM »
sounds reasonable.  It never crossed my mind.  Thank you gents.
*1973 CB750K3 (Bow)

Offline Duke McDukiedook

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Re: #1 Plug cap shocking the H**L outta me
« Reply #4 on: September 29, 2015, 03:04:11 PM »
And this is the obvious observation, "QUIT touching it!!"  :D
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Offline Gene

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Re: #1 Plug cap shocking the H**L outta me
« Reply #5 on: September 29, 2015, 03:25:00 PM »
And this is the obvious observation, "QUIT touching it!!"  :D

Right?  That also seems reasonable.
*1973 CB750K3 (Bow)

Offline Don R

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Re: #1 Plug cap shocking the H**L outta me
« Reply #6 on: September 29, 2015, 07:59:26 PM »
 It is best to replace all the caps so the resistance on both sides of the coil is equal. Good job. And go ahead, touch it.
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Offline Deltarider

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Re: #1 Plug cap shocking the H**L outta me
« Reply #7 on: September 30, 2015, 04:21:39 AM »
I'd start with measuring the caps resistance (please report us) and if necessary buy new ones. You'll probably have to.
I don't see why you should change the leads (which is a bit difficult with stock coils) rightaway. You can clean the leads with some alcohol. Trim the end of the leads 3 mm so the (new) caps will screw in fresh, solid wire. That's probably all what it takes. BTW, arcing is best spotted in the dark.
« Last Edit: September 30, 2015, 04:23:39 AM by Deltarider »
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Online CycleRanger

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Re: #1 Plug cap shocking the H**L outta me
« Reply #8 on: September 30, 2015, 07:38:53 AM »
There is hardly a 750 out there that can't benefit from new plug caps.
Do you have a copy of the Honda Shop Manual or Parts List for your bike? Get one here:
https://www.honda4fun.com/materiale/documentazione-tecnica
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Offline Gene

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Re: #1 Plug cap shocking the H**L outta me
« Reply #9 on: September 30, 2015, 09:34:28 AM »
Thanks everyone.  I'll measure the resistance at some point this week and post, just for posterity, before I replace.  I probably will not replace the leads because they do not disconnect and I don't want, and I don't think I need, new coils. I'll trim the ends clean prior to replacement.

And now . . . . I can't stop touching it . . . .
*1973 CB750K3 (Bow)

Offline Don R

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Re: #1 Plug cap shocking the H**L outta me
« Reply #10 on: September 30, 2015, 12:17:05 PM »
 I think I paid $4 each for new NGK caps for the goldwing. I had one with an open in it, at speed the spark would jump and make it.
No matter how many times you paint over a shadow, it's still there.
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Offline Gene

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Re: #1 Plug cap shocking the H**L outta me
« Reply #11 on: October 08, 2015, 09:14:16 PM »
BTW - took some readings before replacing - and, while I've lost the piece of actual paper I was writing on, I remember more or less the readings.

#1 6.75
#2 7.something
#3 5 +/-
#4 4 +/-

I replaced them all anyway w/120 degree NGKs - re-routed 1 & 4 to reach a shorter cap - I like that better anyway, keep the wire off the head entirely.  If I have totally effed up, please let me know, but I've seen bikes on here w/ the same re-routing. In a practical sense - less distance = better connection?  I dunno, not an engineer.

After all is said and done, the fact is I am no longer shocked when I touch the cap of #1.  And, sadly, I sort of miss that.  But the bike runs great. 

On a quick side note - and moderators, please feel free to archive this (not sure it will be any help to future legions) - you all make me want to be (and I have become) a better maintainer of my vehicle.  I won't bore you with my bike history but it's nice to be back, and the internet has actually made getting back into biking better because of places like this.  Especially for these old bikes.  Which, btw, I wouldn't trade for all the new bikes in the world.  There's a reason we love them, and while some of that is nostalgic there is also a practicality to it.  We can work on them ourselves and keep the machine rolling.  I hope to be a member here for a very long time, and I appreciate everyone's input, even if I disagree with it.  One should have a disagreeable partner every once in a while if, for no other reason, than to have to prove your point more succinctly.

Adios, time for dinner.

Gene
*1973 CB750K3 (Bow)

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: #1 Plug cap shocking the H**L outta me
« Reply #12 on: October 08, 2015, 10:00:45 PM »
#$%* it, it's 40 years old! Replace all of them and cut your wires off slightly. Small price to pay to begin replacing everything on an old bike. Get used to it  ;) OR buy a new bike.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Gene

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Re: #1 Plug cap shocking the H**L outta me
« Reply #13 on: October 08, 2015, 10:47:21 PM »
#$%* it, it's 40 years old! Replace all of them and cut your wires off slightly. Small price to pay to begin replacing everything on an old bike. Get used to it  ;) OR buy a new bike.

Gave 'em all a little snip, and no way - I like old things, especially things that last. F&*k - it was only last month I finally got a phone to replace my Nokia 2003 bar phone.  But, you can't kill the fu***in' thing.
*1973 CB750K3 (Bow)