spark plugs

If it's broken or just needs tweaked

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dkshadow
Posts: 8
Joined: Tue Jun 22, 2010 6:48 pm

spark plugs

Postby dkshadow » Tue Jun 22, 2010 7:17 pm

I am rebuilding my first CB650C and I am confused on what spark plug I should run to get the best performance. The bike has listed on it a few different plugs and other sites have listed different plug and I have heard that if you put colder plugs in #2 & #3 it gets better performance. Any ideas on this?

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Volker_P
Posts: 5508
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: spark plugs

Postby Volker_P » Wed Jun 23, 2010 6:45 am

Welcome here! :D
Choice of plugs depends on fuel, mixture, riding style, altitude, season and some other things. If (e.g. iridium) plugs really can make a change, this is usually a sign that something else with the ignition is not all right any more.
I'd say use the standard plugs unless you don't get ahead with them. The colour of the plugs will tell you if you may need to do a change. A bit of white is typical for a CB650 which is stock jetted close to lean.
It is no good idea to try to compensate too lean mixture with different plugs as it will of course still run lean and hot, but you don't see it any more at the plugs.
So if your inner cylinders get considerably hotter and the plugs look like that, too, first have a look at the cooling fins and the gaps between the cylinders, then make sure that your mixture is all right (e.g. floater level?, ...) before you go to colder plugs.
The whole story might look a bit different for racing.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


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