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The Great Inlet Manifold Debacle

Discussion in 'Maintenance' started by maelstrom, Aug 3, 2016.

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  1. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Hi All,
    So as we all know it gets harder and harder to source inlet manifold rubbers and they are all going rotten. I have to face this problem sooner or later with my own Yamaha 400. Even though mine are not too bad it is only a matter of time before they are useless.

    Now mine are the one piece metal and rubber units. So my solution is to use a two piece unit, and fortunately the 1WG FZR400 uses this setup. I will make the 1WG rubber manifolds in black Viton, no point in using NBR, that is what other people do. Then I will have the matching spigots produced in aluminium so it becomes easy to make your own aluminium manifolds or pay someone to do it for you. These could be used for any bike that uses these carbs (Mikuni BDST 32) not just Yamahas.

    Now for the 250cc, if I can find a similar rubber fitting for the smaller carbs then I can do the same for those. All suggestions welcome.

    These are 1WG rubbers
    [​IMG]
    and this is one of the the standard 1WG manifolds
    [​IMG]

    cheers
     
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    maelstrom, Aug 3, 2016
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  2. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    When I say spigots I mean just the ring that fits into the rubber manifold, not the entire part.
     
    maelstrom, Aug 3, 2016
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  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I have been thinking about rebuilding my intake manifold's for the 3LN3
    I would cut the aluminium base plate's off just above where the nut's do up and then strip off any of the nitrile rubber
    Then make up a steel mould to copy the inner and outer dimension's of the original manifold
    Once that's done i would sit the alloy base plate in position then put a jig over the top to hold it all in position, then mix up some urethane and pour it into the mould
    Once it's just set (still very flexible) you can pop them out and the manifold will be ready to trim up and use once it's fully cured

    Have you seen the Bugpack Urethane VW intake boot's they are now using ?
    I reckon it'd be the perfect stuff to make the top carby to airbox boot's as well as it doesn't shrink or crack like Nitrile does

    [​IMG] [​IMG]
     
    my67xr, Aug 3, 2016
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  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Very interesting, I have only seen it used for suspension bushes and the like before.
     
    maelstrom, Aug 3, 2016
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  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I have seen these Suzuki manifold's too, they are for converting throttlebody's to carby's, not sure on the dimensions though
    They look pretty close to the 3ln3 shape
    http://www.speedwaymotors.com/Micro-Mini-Sprint-Suzuki-Intake-Adapters,80761.html

    [​IMG]

    And some for Yamaha's
    http://www.speedwaymotors.com/Yamaha-Intake-Adapters-2003-2010-S-Model-4-Per-Kit,40602.html

    [​IMG]
    The boot's are available seperately, in the description it mention's non cracking but doesnt say what they are made from
    http://www.speedwaymotors.com/Yamaha-Intake-Boot,62175.html

    [​IMG]
     
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    my67xr, Aug 3, 2016
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  6. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Yes, that is the sort of idea, but I seriously doubt that you will find anything that will bolt on.
     
    maelstrom, Aug 3, 2016
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  7. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Message them and ask for measurements of the oval area of the baseplate. I have the measurements for the stock 3LN ones floating around somewhere after seeing some ones on aliexpress, but they were too small to fit.
     
    Linkin, Aug 3, 2016
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  8. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I have a spare set of 3LN3 manifold's and 2 set's of 2KR manifold's here
     
    my67xr, Aug 3, 2016
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  9. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The 250 manifolds are not curved?
     
    maelstrom, Aug 3, 2016
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  10. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's right, they are straight 'up' in relation to where they mount on the cylinder head, no bends.
     
    Linkin, Aug 3, 2016
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  11. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Yet they all have different part numbers?
     
    maelstrom, Aug 3, 2016
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  12. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Let me get these 400 jobbies sorted first and then I will get back to you about those. All I really need to do is make both sides of the rubber the same as that of the standard manifold. In other words they would look just like the 400 ones pictured above but a bit smaller.
     
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    maelstrom, Aug 3, 2016
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  13. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Nah they are pretty much straight 3LN3

    [​IMG]

    [​IMG]

    The 2KR one's are 32mm i/d and are long, the 3LN one's are 34mm i/d and are short
     
    my67xr, Aug 3, 2016
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  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Ok, and the oblong holes add another layer of complexity. :headbang:
     
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    maelstrom, Aug 3, 2016
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  15. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The 2KR manifold's on the top use 2 of each manifold, all have the same bolt spacing
    The 3LN manifold's use 4 different manifold's.
    The 2 inner manifold's have the same bolt spacing as the 2KR manifold's
    And the 2 outer 3LN manifold's have a wider bolt spacing so you can't even use an earlier 2KR head on the 3LN easily


    The 2KR manifolds have a raised alloy tube from the base flange up inside the rubber though, it goes up 15mm approx inside the rubber so you might be able to trim back the rubber and use a rubber tube type manifold and clamp it to the base

    [​IMG]

    [​IMG]
     
    my67xr, Aug 3, 2016
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  16. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    If they are straight then perhaps it is that different bolt centre and position of vacuum fitting that makes the difference.
     
    maelstrom, Aug 3, 2016
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  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    It would be good if just one piece could be cast in aluminium for all four. I will look into that too.
     
    maelstrom, Aug 3, 2016
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  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Just looking at these manifold's again, i have them the wrong way around if the marking's are correct, there is a 3 and a 4 moulded into the top's

    I think the 3LN manifold's are too hard to make from scratch, the 2 inner carb's are also offset in toward's the centre of the engine so the carby's sit about 6mm off centre from the inlet port
    It's a bit hard to explain, but 1st pic below is manifold 3, second is manifold 4
    This must be due to the carby body's being wider or something ?

    [​IMG]

    [​IMG]
     
    Last edited: Aug 3, 2016
    my67xr, Aug 3, 2016
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  19. thebeefsalad

    thebeefsalad Well-Known Member

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    Willing to whip up a set for an RD400/RZ350? A (Canadian) buddy just picked up an rd400g, and makes it sound like rz350s have common intake manifolds.
     
    thebeefsalad, Aug 4, 2016
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  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    I think you can find those on eBay or similar.
     
    maelstrom, Aug 4, 2016
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