How to check flapper?

If you removed the hose did you blank it off ?

The flapper won't open below 1/3rd throttle or 55mph i think from memory so you won't see it move just running in you drive.

ok... I gotta ask. What the hell is "The Flapper" :dunno

It's a French Slapper (only joking)

The post 04 rsv's have a flap that drops down to close the air intake below 1/3rd throttle or 5000 rpm. (from memory)

The official reason is partly for reducing induction noise for emissions testing and partly to smooth airflow over the Tb's at low speed where pulsing can induce surging and generally upset the fueling consistancy.

When the bike first hit the market a popular mod was to disable the flapper and get as much air in as poss at all revs
Some aprilia tuners in the Usa have more recently looked at the figures behind it all via dyno etc and say that there is something in it and the bikes produce slightly better fueling with the flapper enabled if your a road rider and use low speed fueling more.
They also found the later (post 04) bikes often fuel worse low down and produce little or no power gains with aftermarket airboxes over the standard version for road use. The race teams in the US powerbike series are all running standard airboxes. Official Aprilia teams and not.

For once Aprilia seem to have done their homework here

If you look into the Ktm rc8 fueling they have gone much further but the crux is less undisturbed air around the Tb's is better for low load fueling than lots of disturbed air

Cheers Spoonz!

great discription spoonz