I have had the similiar problems to what buck had yesterday. Funnily it seems to be a random thing...like I was riding behind Buck and my 7 wasn't affected...however his 7 was. Maybe it was the flames comin out the zaust warmin' the air ....

On the last ride thru the spurs my 7 was affected Buck's 7 wasn't???
It only seems to occur when there is cold air or mist around. Like I rode the spurs over three different days in a week and it happened at different places along the route but always when it was cold or damp???
The bike feels and sounds like it's running on 3 or 2 cylinders and clears if you coast and give it a few revs but depending on the conditions returns again quickly. If you stop and allow the heat to sink thru everything for a while, it usually starts with a bit of an effort and coughs and carries on and then it clears and runs ok.
I was thinking that some sort of ducting from just behind the headers and pointed at the carby bodies might be a help???? Dunno. Some cars have this same sort of ducting except they generally duct it into the air cleaner and they have a cold air flap on the nose of the air cleaner to block the external cold air.
Be interesting to have warm air funneled into the air box system and then block off the front intakes. Dunno that it would be a good idea to block off the air volume into the carbies without an alternative air source because that could affect performance badly...I'm guessing. Maybe warm air ducted, in a reasonable size ducting, into the air box from near the headers and then the front ducts blocked off, might fix the problem. Be interesting to see.
Or is Mina right and I should get out more....
