Drilling the airbox

[johnnyXS]

I have a spare airbox and have been thinking about drilling it for improved air flow on my LiS150 22mm Jetex AF Clubman . I have already removed the baffle from the air scoop but nothing else yet.
I have noticed however that under sharp throttle opening that the rubber air hose collapses which indicates that insufficient air flow is being supplied under hard acceleration

HAve done a bit of searching but cannot find any concrete evidence that this makes a worthwhile difference to performance. There is plenty of ........'yeah just do it dude' kind of advice but no real record of actual performance improvement .

has anyone actually done this on their 150cc and what improvement did you see ?

[EddieStone]

I was in the same place as you and I decided not to drill my airbox.

As I see it, drilling holes in the airbox means the carb gets the warm air from under the sidepanels rather than the cooler air outside the scoot via the scoop. I think it's viable if you're running without sidepanels, but I'm not convinced otherwise.

There is usually a drilled one on eBay if you need one. I think some airboxes have a dent in one side that restricts airflow through the airfilter - drilling this is supposed to help, but so is getting a different air box.

[johnnyXS]

mmm thanks eddie ..thats pretty much all I have been able to find out from various sources too.

I don't want to start hacking my original airbox around but I have come by a spare series 3 airbox but it hasn't got the later GP bulge around the air filter.

I suppose I could just drill it out and swop the airbox over and give it a test but its bloomin cold out there in the shed and I expect it will require the carb rejetting too . I'm not too keen to take the scoot out when its wet and icy either so maybe its something to shelve until its a bit warmer next spring

I found this thread which hints at an improvement but nothing concrete
http://www.network54.com/Forum/325727/thread/1090867136/To+drill+or+not+to+drill+!

[Phil D]

Hi Johnny
I just had a thought when you said the airbox bellows were pulled in under throttle.
I had the same problem and replaced with one that was a lot stiffer , it wasn't deformed under throttle load and keeps it's shape .
PM me if you can't find one and I'll sort one for ya.

[johnnyXS]

Hi Johnny
I just had a thought when you said the airbox bellows were pulled in under throttle.
I had the same problem and replaced with one that was a lot stiffer , it wasn't deformed under throttle load and keeps it's shape .
PM me if you can't find one and I'll sort one for ya.

thanks Phil.
As a temporary measure I put a coiled spring from a huge ladys hair curler inside . ( Huge curler not huge lady lol)
Its done the trick for now.
As soon as this Vertigo has gone I'm going to fit a foam filter and rejet and see what effect freeflow air has on starting running and performance . I have always run without panels since the 60s so there should be abundant air supply but perhaps at speed there may be a low pressure area around the carb I'll have to see.

I'd appreciate it if you could PM me the linky please Phil

[Hammer RB230]

JonnySX

I have a LI150 with a 175 top end. I have removed the bridge in the air scoop and the baffle within the air box . I have not drilled out the box as I didn't want dirty warm air entering the carb etc. Instead I fitted a BGM fast flow filter. JB Tuning set the engine up for me, and John was amazed how much improved the air flow was, in fact he was surprised how large he had to go with regards to jetting. Apologies I can't remember sizes.

I would recommend using the BGM filter with the air box mods I've mentioned. It also makes a great induction noise from underneath the seat.

Cant help with regards the rubber collapsing but I'm going to check mine now!

Hope this helps.

[johnnyXS]

thats very interesting Jonny .
I have a spare filter box so I don't mind hacking that about to experiement with .

A High flo filter should be a good investment......... although at nearly £ thirty quid I couldn't justify that expense and it smacks of profiteering to me

[Phil D]

I put a coiled spring from a huge ladys hair curler inside .

That'll work .

[hullygully]

your bellows collapses cos its an Indibum one, mine on my drilled out box used to go in & out like a set of lungs till it completely exploded, pay that bit extra & buy Italian
as for drilled airbox sucking in the warm air from under your side cans..............mine went to this years Euro & back (now that WAS hot hot hot) with NO heat seizures on a cast Gori 200 top end on a TV block