misfire on number one

Posted by Disneydave on Nov 01, 2007; 11:48pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/misfire-on-number-one-tp457313.html

I have a 1972 CB750 K-2 with 23,400 miles on it.  I rebuilt the whole bike from the ground up in 2002 and have just fired it for the first time since 1992. I just last week rebuilt all the carbs.  The bike is original except for an allan key bolt set and a Dyna S ignition.  Now that it runs it runs very well above 4200 RPM but below that the #1 cylinder backfires quite a lot.  I have changed plugs and checked all the electrical connections and grounds.  Coils and wires as well as plugs are all OEM new.  New gas also -- before anyone asks.   Would this be a timing problem with the Dyna or maybe a bad coil??  Any suggestions not costing thousands of dollars would be appreciated.
Thanks
Dave