If you mean the two listed in the Honda parts book, the performance plug runs a little colder
because the motor is turning faster, thus as it has less time to cool down they list a colder plug.
If you mean you are running a special plug like iredian then it is because the plug firing end is
out in the open and the fuel can get closer to the firing spark and it ignites the mixture easier.
From: Jean Luc Picard <email@example.com>
Sent: Saturday, October 15, 2011 3:43 PM
Subject: [Honda-C70] New performance spark plug
Just got a new spark plug special ordered from O'Reilly, & I swear I'm accelerating just a little bit faster. Then again that probably also has something to do with my old dirty spark plug backfiring...
Does anyone know exactly how the 'performance' spark plug listed in the service manual does that the stock doesn't?
[Non-text portions of this message have been removed]
1970-73 C70 Honda Service Manual: http://tinyurl.com/6ebwtw
1970-73 C70 Troubleshooting Guide:
http://tinyurl.com/6ebwtw (scroll to sec.7.1 page 101.jpg)
1980-83 C70 Honda Service Manual: http://tinyurl.com/hu42c
1980-81 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec.18-1 page 170.jpg)
1982-83 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec. 20-28 page 205.jpg)
1980-81 C70 Maintenance Schedule: http://tinyurl.com/z4zn6
1982-83 C70 Maintenance Schedule: http://tinyurl.com/hw35c
More resources for C70 Passports and Cubs: