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  1. #1

    Suzuki 750 Kat Air Box Lid

    Hi Guys,
    I have a Japanese import 750 Kat. Had a pretty major lag on acceleration until I took the air box lid off. Runs well now but has anyone done anything with carb settings on a stock bike with stock exhaust. I'm about to raise the needles one clip and adjust the mixture screws accordingly......any thoughts?
    Cheers
    Kentg

  2. #2
    Hi,
    Did you check the main jet? If you took the air box lid off and Kat runs well, mixture is rich. Main jet of JDM's 750(type1&2)is #112.5.
    Cheers

  3. #3
    Welcome and don't forget an intro when you get a chance.

    Big mistake is to chase a setting. If your intention is to run stock (bearing in mind how much people like to modify Kats) then you should consider what I did. I put a stock system back on my 750 Kat (had 4-1) and had awful problems even though the jets were the right number. It would foul a plug going around the block. Fiddled with clips and mixture and all that. What I didn't see until about 4th time out was that someone had drilled the jets. So I bought a stock set from Mick Hone and replaced the lot. Returned all settings to standard (mixture etc) and ran perfectly out of the box and even bought back an awesome mid range that was missing. If you start playing with one part of the system (eg remove airbox lid) you'll only move your issue somewhere else in the system particularly if you don't know what has been done to the bike previously.
    Gone riding!

  4. #4
    Moderator QLD drillit's Avatar
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    .....so how much did it cost you to buy back the missing mid-range?

  5. #5
    OK
    But you missed my point. This thing is bog stock( standard jets and correct float height) with 6000K's on it and when you pulled the throttle on to overtake (roll on or going back gears) there was a lag. Air box lid removed solved this issue. Obviously the factory sends them out jetted for as is (air box lid on) Most Suzuki's I sold over 20 years went a lot better with the air box breathing better. So tuning has changed and will require tweaking to make 100% power. So are all you Kat owners running around with the Air Box lid on? My friend Has a Kat 1100 and GSX1100E both no lid?? And trust me his 1100 has ballsy linear acceleration to red line.

  6. #6
    Senior Member NSW Tomcat's Avatar
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    Hi Kentg
    Firstly, I'm sure the forum members would appreciate something from you in the Introductions. Cannot miss it, it's the top of the post lists. Nothing War & Peace, just a quick intro of you, your rides and Kat history.

    As for the air box lid, yes had same problem with my 750 and also know a few 1100's with same. Issue is not getting enough air. In the early days Kat owners also used to:
    A- remove the rubber inlet Venturi from the air filter box to gain a larger opening and "more air".
    B- drill a second hole next to the original, or open the first hole to an oval for "more air".
    C- remove the grey sock f Om the filter element.
    D- remove the lid completely, however there are concerns with no lid that in heavy rain the water can run down /past the tank and wreck the filter element, and in southern states if a bike is outside during winter the condensation can wet the element.

    Personally, I use a longer screw on the filter box and a couple of washers to just raise up the rear edge of the lid enough so that air enters around three sides. Result, runs better, no risk of rain or condensation as lid is still in place.

    Caviets however;
    ~ No idea how many k's on mine.
    ~ engine compression test during resto showed only 6 ( manual says rebuild if below 7 - should be 9 ).
    ~ none original exhaust ( no idea of make ).
    ~ non- genuine jets ( I do have a full range / set of original mikunis for when I do engine to 816 ).
    ~ always smells like it's getting too much fuel at idle!

    Anyway, that's my take.
    Cheers
    Stuart

  7. #7
    Interesting Stuart as I never have experienced this with either the 750 or the 1100 and my box is sown up tighter than well um........

    As for the cost young Drillit it was about $800 landed in Australia for the exhaust system, took an age to find the middle section, and the jets were in the mid $100's if I remember correctly.
    Gone riding!

  8. #8
    Senior Member NSW Tomcat's Avatar
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    Totally agree Pkay, changing one thing generally means you have to change another and on it goes.
    My 750 back in '84 was perfect, but I did get it with only 1750 k's on clock!

    My issue is bad compression which not easily fixed, none genuine jets from aftermarket supplier in Japan and non-stock exhaust which ha Ve no details on.

    Also Nick K was the one who put me onto removing the lid as he has done with his.

  9. #9
    Quote Originally Posted by Kentg View Post
    So are all you Kat owners running around with the Air Box lid on?
    What's an airbox?

  10. #10
    Senior Member VIC
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    Interesting dilemma, airbox or not? I have 2 x 1100 Kats, before these there was a succession of (5) pop up Kats. Never came across this issue of no acceleration due to airbox lids.

    I've always kept the air intake stuff standard, except for one of the 1100 Kats now has flat slides and pods. Even so, every now and then I put the standard carbs and airbox etc in place, runs fine. In fact I remember having to make an airbox lid for a recently rebuilt 1170 Kat my son has. That bike didn't have a lid, otherwise standard carbs etc and it runs great.

    So, I guess what I'm saying is that if you have to lift the airbox lid to get the bike to run clean, there is something amiss in the carbys. Go back to bog standard with the carbs. Do not trust anything that is internal, check everything as previous owners do some 'interesting' stuff.

    Happy hunting!

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