Airbox what's missing

[Tomzed]

Hi I'm wondering if any one can tell me what's missing the pipe from the airbox to the carb has another outlet on it and there's nothing there. Just an open pipe
My bikes a little lumpy low down wondered if this could be causing it
Or could it be that the previous owner has drilled about 6 or 7 12mm holes in the top of the airbox under the seat
It's on standard jetting

Appreciate any help guys thanks

Also it's a mk3

[knackeredMk1]

There should be a plastic 'bulb' attached to the pipe. Also called a 'boost bottle'.

If the pipe is just left open - really really bad. Your engine is just sucking in unfiltered air with all the problems this brings with it.

If the pipe is closed off - Will only make a slight difference to the engine running. May or may not be the cause of the lumpy running. Best get it replaced. The AR and Mk3 are different I believe though either would be better than what you currently have. In the mean time be sure that it is closed off completely.

The holes in the air box won't make much difference.

[Tomzed]

what does this boost bottle do is it worth having or should i just blank it

[fallenmikethebike]

To be corrected by other possibly, but generally, the boost bottle stores a small residual charge of mixed but unburnt fuel.
When the throttle is opened, this is taken in and helps smooth out the intake rush.
Years ago on an old open class YZ490, to help tame the beast I tried taking of the boost bottle, this did tame it slightly, but at the cost of some very lumpy running.
Mike

[Tomzed]

Found the bottle in some spares that came with the bike fitted it today and it runs loads better over run isn't lurching as well
Thanks for the help