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Old 02-23-2014, 09:26 PM
Theon Theon is offline
Motorized Bicycle Elite Member
Join Date: Jan 2014
Location: FNQ Australia
Posts: 1,440
Default Re: Small bubbles at spark plug thread

I was meaning to ask how you went with that,
Excellent, I was taught to gap a plug to 20 thou.
A hacksaw blade, or my thumb nail seems to be about right.
A little more gap is good if you have a high power ignition, but for general Lawn Machinery,
Which these motors really are, 20 thou works for me.
And gets me 8500 Rpm with out any trouble.
My 9500 RPM motor runs a 500 Ohm Mag and standard CDI (as yet), No problems.
In a straight fire head I run either the B7HS and remove a couple of threads (photo1), or a Z4JC 3 prong Plug and remove a couple more threads from the head (2). The standard Z4C that comes with your EBay Kits sits way to deep into the plug recess, and I do not use them for anything (3).
With an Angle fire Head I use a BP7HS and again remove a couple of threads (4).
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