Originally Posted by Conrice (Post 1224481)

i find it hard to believe you had a noticeable a/f mixture change by taking off the fairings....what makes you think you're running lean? and as far as the vent tubes.... i haven't messed with f2/f3 carbs in a long while. i was looking at some other pictures on-line - don't the vent tubes run to some sort of valve or box looking thing? and then they go up to the front of the box by the air tubes that lead into the airbox?

have you messed with your pilot screws at all?

Originally Posted by Mustapha dump (Post 1149811)

The main cause of issues when the fairings are removed is the float chambers seeing a slightly lower pressure than the airbox sees when moving at speeds above 45mph or so.
The ZX series of Kawasaki sportsbikes suffer from this problem very acutely.
What you really need to do rather than restricting the amount of air entering the airbox, is to enable the float chamers to see the same pressure reference as the airbox.
The easiest way to accomplish this is to find the two Tee pieces between carbs 1&2 and carbs 3&4 which are the float chamber vents, on some banks of carbs on the Hondas it is one large Tee piece between the 2&3 carbs as all 4 carbs are linked across the top.
Once you have determined the float chamber vents, attatch a short length of rubber hose to the Tee piece, and then run it into the airbox through a hole drilled in the underside just large enough to pass the hose through tightly.
Face the open end of the hose towards the front of the bike under the airfilter, if needs be slash cut the hose at 45 degrees and face the cut upwards and forwards.
By doing this the float chamber vent will be fed by the air entering the airbox which then ensures that the pressure in the float chambers is equalised with the airbox pressure, once this is achieved the air passing through the venturi will suffer a slight pressure drop, as this happens the air pressure in the float chamber becomes slightly higher than that in the venturi directly above the needle jet/jet needle, and this higher pressure in the bowl then forces the fuel up the needle jet/emulsion tube and introduces it to the airflow through the venturi where it is then atomised and carried into the cylinder.
I've had to sort out quite a few "Ramair" issues on sportsbikes that have had the fairings removed over the years, in the past the issues have been difficult to detect as they don't generally manifest when I have the bikes on my dyno, although I now have a dedicated ducted fan which I use to blow air into the airbox intakes in an effort to replicate the problem as it occurs on the road rather than me going out and testing the bike on the road myself which isn't always a practicable option when it is pissing down with rain, or during the summer when the local roads are crowded with tourists heading towards the coast.

Originally Posted by Conrice (Post 1224624)

but i just don't see how anything changes. your carbs get air from the airbox - and that hasn't changed.

Originally Posted by Conrice (Post 1224624)

pictures of your carbs would help so i can see what's going on. i remember what the vent tubes look like - they're 5/16 openings or so in between the carbs right? where are they going right now?

Originally Posted by Conrice (Post 1224624)

barometric pressure is barometric pressure. i don't see how no fairings could create a substantial difference - regardless. AND you're not the first f2/f3 streetfighter - and i haven't heard of this problem before. look at fathead's f3 fighter build or knifemaker's f2 build on CF. they're completely naked bikes - and i don't remember any mods they had to make in order for their bikes to run

Originally Posted by Conrice (Post 1224665)

...seems like your little t would work, but i'd go ahead and trying doing two separate tubes in there