Motorcycle Repair: Bout My 82 CB900C, air fuel mixture, pulse generators

Question
I own a Cb900C. Just had the carbs cleaned and bike tuned etc. But a few days after I got it back, it began while riding it for 20-25 mins at highway speed to shut down & then it usually quits and wont start up again for 20-30 mins. This has happened a few times...
Today it ran for about 20-25 mins and then it began the same symtoms but didnt completely shut down it sounded like it was running on just 2 cylinders. THen after riding it for 15 or so more minutes the symptoms went away and it fred on all 4 cylinders.
When i got back home i looked at the plugs knowing that cylindrs 1&4 are on the same coil and 2&3 are on te same coil thinking that maybe I had a bad coil. But oddly enough Cylinder plugs 1&2 looked clean and 3&4 were "carboned up".
Do you have any ideas? ive been told it could be the pickup coils in the pulse generator or the ignition coils maybe even the igniters...HELP!
Thanks, Mike

Answer
Doesn't sound like coils to me because the coils, pulse generators and ignition modules control the 1&4 and 2&3 plugs so having 3&4 act up indicates it's probably not the ignition.  I'd bet you have something going on with the carbs. My first thought is that they didn't get the float levels set right and it running too rich fouling the plugs.  If the carbs are too rich (less that 13:1 air fuel mixture) the plug won't ignite the fuel.  I just can't explain why it works intermittently.  When it starts acting up, can you turn the fuel off and see if it clears up some?  If it does clean up some, it's definitely fuel related.  


Regards
Rich