Author Topic: Spark Plug lead routing question  (Read 1887 times)

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Offline paul25g

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Spark Plug lead routing question
« on: February 24, 2010, 04:03:23 PM »
Hi all,

I have a question about the routing of the spark plug leads from the ignition coil on a 175 Dual Twin.  This is my first shot at restoring a multi-cylinder bike, which was in non-running condition when I got it.  I’ve rebuilt the motor and am starting to put things back together.  When I got this bike, the right spark plug lead went to the spark plug in the left cylinder and the left spark plug lead went to the spark plug in the right cylinder.  This just seemed backwards to me but there was no specific info in the repair manuals.  I assume this had been incorrectly assembled in the past, but maybe it doesn’t make a difference?  Just curious before I start the timing procedure, can anyone shed some light on this?  Thanks in advance!

Paul
1958 BMW R60, 1966 BMW R50/2, 1972 Triumph TR6R

Offline OldSwartout

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Re: Spark Plug lead routing question
« Reply #1 on: February 25, 2010, 09:33:36 AM »
It makes a difference in a way. Each coil only fires once per revolution and you can't switch the plug wires back and forth as the spark would end up 180 deg off with them one way. If they were crossed, it just means the leads from the points to the coils were also crossed.  No big deal, but IMHO, you're better off if the plug wires don't have to cross each other and the frame backbone.
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline paul25g

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Re: Spark Plug lead routing question
« Reply #2 on: February 26, 2010, 07:57:07 AM »
Thanks for your help Karl!
1958 BMW R60, 1966 BMW R50/2, 1972 Triumph TR6R

 


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