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Vespa Labs > Vespa Tuning > Carburetors & Carburetion > Air Filters > Air Filter Hole

Air Filter Hole

From $1

    Table of contents
    1. 1. Warning

    It is possible to drill holes in the standard SI24 carb air filter. This allows the carb to suck air more freely and, combined with correct jetting (normally a slight increase in main jet size and check it is correct by reading the spark plug), gives a cheap and easy performance boost. It is also possible to buy a filter which does not require the drilling (see below).

    The reason that the holes aren't there on our scooters in the first place seems to be that the US and Australian markets were provided with detuned carbs (someone from Europe please confirm). This is just a guess and the fact that old Pinasco installation instructions talk about drilling a hole, suggests that "holeless" carbs were also sold in Italy in the past. This could also be a Cosa airfilter.

    ./European air filter.jpg

    Dyno results show that the having a this hole provides a pretty big increase in power and at the cost of a main jet, is probably the best value for money performance enhancement you can get. See Air Filter Hole and Sito Plus lab results for more detail. 

    Here are is a picture showing the difference in air filters and the approximate size of the holes. You can use a drill to match these holes in your original filter, taking great care not to leave swarf in the filter.

    original_vs_holes.jpg

     

    Warning

    The fact that there are two different types of air filters means that you should also take care when replacing parts. If you have an original "no holes" air filter the get a "holes" replacement, if you do not change you jetting you run the risk of heat seizing your scooter.

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    Comments (11)
    Viewing 11 of 11 comments: view all
    #1
    vespavintage says:
    I've done this to my PX with a 118 main jet and Sito Plus exhaust. Is there anything I can do with the other jets? Just seems to bog down a bit on take off.
    Posted 00:31, 13 Oct 2008
    #2
    internetscooter says:
    I plan to do some testing with an oxygen sensor at some stage so I don't know for sure. Low down you should play with your mixture screw.

    Hopefully with the oxygen sensor I'd be able to measure just how much each jet impacts over the whole range.
    Posted 21:45, 21 Oct 2008
    #3
    vespavintage says:
    I suspect something is up with my carb. Twist throttle to take off, delayed engine revving. Or maybe I am after something a little more responsive/sensitive.
    Posted 17:56, 12 Nov 2008
    #4
    F64VAL says:
    hello there. how much would it cost to do the hole and sito setup ? thanks
    Posted 03:25, 20 May 2009
    #5
    internetscooter says:
    The hole is free (make sure you clean properly after drilling). Sito exhaust will cost differ depending on country. I think about $150-200 for Australia.
    Posted 19:24, 20 May 2009
    #6
    mini_me says:
    Thank you very much for this information. ;-)

    I tried this the other day by making a heart shaped hole (Would this thing have a negative effect?) instead. 118 is not readily available so I tried 120 and made some minor adjustment on the A/F mixture screw, so far the spark plug looks OK. edited 00:18, 27 May 2009
    Posted 00:04, 27 May 2009
    #7
    internetscooter says:
    The indent is heart-shaped, the extra hole is in the top part of the heart. Drilling out the whole heart shouldn't have any negative effect (as long as the jetting is right). 120 should be nice and safe.

    I'll add a close-up photo tonight.
    Posted 02:38, 27 May 2009
    #8
    vespavintage says:
    And it sucks more fuel too. I find I run out a lot quicker but have a nicer mid range.
    Posted 05:21, 27 May 2009
    #9
    Dedalo says:
    I tried adding these holes to an SI air filter, upjetting to 120 (I may have got away with a larger jet -- not too sure at this point) and putting the air filter on top of an SI26 carb (from SIP). Don't know if the scooter was any faster, but the engine was significantly gutsier, if you know what I mean. edited 22:45, 15 Apr 2010
    Posted 22:42, 15 Apr 2010
    #10
    SCOOTGP says:
    i have owned a 1981 p200e for 10 years now,the previous owner left it standing in his garage for 18 years. I stripped the engine and fitted new seals and bearings rebuilt carb and repainted her.in all these years ive never been able to get her to run just right it always felt like she was struggling. after numerous exhaust and jetting trials i finally checked the air filter and yep no holes after drilling it out and running 118 main jet she absolutely flies and is so much more responsive through the revs and thats with the standard exhaust fitted.
    Posted 01:33, 7 Sep 2011
    #11
    Jackman6944 says:
    Hello
    I have drilled the extra holes and even stripped a layer off the wire mesh of the air filter.It does make a lot of difference to the power.However if the jetting is too big then you will experience delayed revving on takeoff.Have tried many exhaust combinations to this setup and found that using a Proma sports pipe is the best.Too bad here its considered an illegal mod.
    Posted 20:16, 17 Jan 2012
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