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Air box on Honda DOHC carbs

Discussion in 'Motorcycle Tech Talk' started by treeborn, May 4, 2010.

  1. treeborn

    treeborn New Member

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    Greetings all. This looks like a Harley site so I hope you don't throw hard, sharp objects at me for bringing up a Honda but I got here because I learned that Ken was a CV carb expert. I belong to the Honda DOHC forum (1979-83?) and own a 1981 Honda CB750 converted to cafe style. The Honda forum goes on an on about the necessity of the original air box/paper air filter assembly in order for the carbs to work properly and are constantly disparaging POD filters. I put PODs on mine and it seems to run fine. What's all the fuss Ken?
    treeborn, May 4, 2010
    #1
  3. chucktx

    chucktx Moderator Staff Member

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    i think all the fuss is that the boys over on the honda site......i cant believe i just typed that word!!!!!!..................are wanting to keep things stock and original. there is no problem with aftermarket components in the airbox, actually they will preform better.........have fun and stay safe!!!!
    chucktx, May 4, 2010
    #2
  4. FLHTbiker

    FLHTbiker Moderator Staff Member

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    We no longer own a Honda, the wife sold her Valk Trike, now its all HD and a bit more room in the shop. The Honda boys don't know as years ago I had an 82 CB750 with aftermarket air filter and ran better.
    FLHTbiker, May 4, 2010
    #3
  5. cowboy

    cowboy Moderator Staff Member

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    had a 76 750 first thing I did was drop the stock pipes & air box , went 4 into two header set up & single filters on each carb , Ran great after that
    & welcome to the site
    cowboy, May 4, 2010
    #4
  6. hotroadking

    hotroadking Super Moderator Staff Member

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    First, welcome
    second, you got a picture or two of the bike I'd like to see it.

    Most of us just like motorcycles, one of my first was a GS400 Susie
    it was quick and fun... Wish I still had it, it'd be a bobber by now maybe LOL

    To the question, not being an expert on all things honda but
    I'd imagine the design of the air box was to maximize several things
    from the factory, one would have been less noise (EPA)

    Aftermarket filters are not a problem, they may require you
    to rejet the carbs in order to get a good fuel/air mix

    Many folks on HD's run a K&N type insert filter replacing
    the stock paper filter...

    I can't see why it would hurt other than needing to tune the carb (add fuel)
    hotroadking, May 5, 2010
    #5
  7. treeborn

    treeborn New Member

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    pics

    Attached Files:

    treeborn, May 5, 2010
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  8. treeborn

    treeborn New Member

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    Thanks for the note. The DOHC guys are referring to the '79-'83 models that use constant velocity (variable venturi) carbs. (Your '76 used fixed venturi carbs.)

    Ken, they keep talking about the need for "intake air restriction" for the carbs to work right. They claim that without the original airbox/paper filter the carbs will lean out and burn valves. I've got 7,000 miles with no problems yet. Aren't these carbs similar to the Harley CV carbs?

    Ron
    treeborn, May 5, 2010
    #7
  9. hotroadking

    hotroadking Super Moderator Staff Member

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    Nice bike

    A cv is a cv, the velocity is subject to the demands of the engine it moves up and down to keep the air moving quickly and at the proper rate

    Now going to a less restrictive filter without the box will lean out the fuel mixture, that means you may need to increase the pilot jet one size, maybe change the needle and
    adjust the idle air fuel mix screw..

    Best way is on a dyno.

    The point being your friends are correct a less restrictive filter system will lean
    out the fuel mixture, but that doesn't mean it is going to burn it up, unless it's super lean..

    Now if it is very lean it could cause long term damage.

    with that performance pipe and the filters you need to consider finding a dyno operator that can put a sniffer in the pipe and tell you your HP, TQ and give you an AFR reading.
    hotroadking, May 5, 2010
    #8
  10. chucktx

    chucktx Moderator Staff Member

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    nice bike!! i like the colors......orange and black!!!!!!!!! lol agree with hrk....more air in and out means ya need a bit more fuel in the engine........and you will get a lot more performance..
    chucktx, May 5, 2010
    #9

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