Just tinkering with my Vortx and noticed that the AIS intake pipe that is routed into the panel filter is incredibly noisy and putting my finger over it quietens the whole car down substantially Is this actually normal!? It's sucking away pretty hard which is partly the noise but it also sounds like it's transmitting general engine noise as well. Any harm in plugging it? Presumably it would just stop the AIS system from doing anything.

Take the AIS housings off and check the reed valves are OK. If one of those is dodgy you'd get exhaust noise through the pipe. The AIS doesn't do a lot so I wouldn't worry about blocking it (I had to bung mine to get it through emissions at SVA anyway). You really need to do the breather mod' anyway if it's a 5vy and that is effectively an AIS delete anyway.

Should have mentioned it's a 5PW so doesn't need the breather mod. It just has the crankcase breather going to a catch tank and then to the panel filter

Not sure how the system works on the 5PW, it doesn't have the ports on the camshaft cover. I'll maybe just block off the pipe for now if it does no harm, it makes the engine sound so much smoother!

Actually I was just reading up on the AIS delete and was wondering if I could get away with just using some silicon blanking plugs to block the 4 angled pipes that run into the head (rather than tapping them and using screws)? If they leaked or blew off would it cause any problems? I guess you'd be venting exhaust gases straight out of them but it'd be obvious it had happened from the noise.

Yeah will be fine, will only blow off if you turbo/supercharge it!

Well I haven't got round to removing the AIS completely but I blocked off that pipe with a bolt and took it for a quick spin...my god does the car feel better Can't see how it would make any difference to performance but the fact that it sounds so much more refined and smooth certainly gives that impression. Might even help me get through noise tests at track days, best £0 I've ever (not) spent.

I think the suggestion about a reed valve stuck open is a good bet maybe, it doesn't seem right that the system should create so much noise if it's working properly, or maybe on a standard bike the airbox just quietens it down?

[Edited on 9/5/17 by T0MMY]