Air screw all the way in

[brewsky]

The idle screws are not always air screws, sometimes they are fuel screws...not sure about the 450's.
At any rate, sounds like it is too rich at idle from something else...maybe float valve sticking open or float not adjusted correctly, or float with a hole in it, air passage clogged, etc.

[teazer]

I missed teh reference to CB450. The CB450 carbs are completely different and the MIXTURE screw does not change the air: fuel supply the same way. It modulates the air and fuel mixture discharged ie it changes teh amount of air and fuel which have already been mixed. IN a regular slide carb, the screw modulates AIR only. CB450 modulates the mixed fuel and air, but it doesn't modulate all the mixture - only the portion that discharges downstream of the butterfly.

there's a second outlet more or less just upstream of the butterfly.

I would carefully clean out the airways and the tiny orifices from which the slow mixture discharges.

Then I'd double check the synch from left to right and then I'd back off the idle speed screw slightly.

Then, when the idle is right, I'd adjust the mixture screws to get it right just off throttle.

CV carbs are typically very different to slide carbs.

[versuspop]

thanks for the help! i know this post is out of place on the 305 forum...

[brewsky]

No problem from me on non 305 questions, as I have asked some myself!

There are obviously members on this forum who have knowledge of other bikes and who don't mind sharing it.

The only "proper" place to post such might be the "Off Topic" section?

If the original poster of a question non-305 related identifies that up front, that would keep replies more specific, and without the wrong assumption.

Let us know what you find out on your 450.