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PHBH30mm carbs - T3 manifolds

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Gfiver View Drop Down

Joined: 26 May 2017
Location: Somerset
Status: Offline
Points: 99
Post Options Post Options   Thanks (1) Thanks(1)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 2019 at 09:32
Some progress.
     I've had it running, but depite Steine Dinse's assurance that the carb's jets, needle'etc are correctly set up, its not right.Much better than the 36mm pumpers on upper throttle range. On the 30mm carbs it just zooms up through the gears like it never did on th bigger carb, but there's an awkward spot, just in the wrong place for pulling away from a stop without using extra revs.
     Looking for the cause has made me realise that with the std. T3 type manifolds, the left hand, marked "S" has a sharper bend, tucking the carb further in under the frame tube. This does make it difficult to get the carb top off and spring and slide out. Not impossible, but tricky enough to make loosing the carb top "O" ring far too easy.
     "If only the "S" elbow didn't turn in so much" I wondered, "Like the "D" one".
So I tried it. Swopped the "D" elbow onto the L/H head & carb, upside down, but that makes no difference, and Bingo! there's the new L/H carb sitting just as the R/H does but 18mm further back (because of the off set of the 2 cylinders) Space for air filters looks like it will be still more improved, but what about the bell housing nuts ?
     Acres of space between L/H carb and offending nut, so much that I removed the carefully crafted 20mm spacer and even with just the 2 std. insulating gaskets, nut and float bowl clear each other nicely.
    But what about the R/H side ? Swapping the "D" elbow back to the R/H carb, with just the 2 std. gaskets, the nut and float bowl do just touch but a slight tilt of the carb on its rubber, or maybe one extra gasket and it'll be Ok.
    All I need now is an extra "D" elbow, but Ebay will provide.

    If those not familiar with older big block Guzzies with these inlet manifolds wonder why on the standard set up, left & right hand elbows have this different bend, it would be so that left & right carbs line up with the original air filter housing, despite one cylinder being 18mm further back than the other.
    So if you are happier with separate K&N style air filters, why not fit a "D" type elbow to the L/H side and have much easier access to the carb, whether its square or round slide instrument?

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Chris A View Drop Down

Joined: 15 Dec 2018
Location: France
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Points: 30
Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 2019 at 12:03
Glad it's all "sort of " working out" . Perhaps a slide with a larger cutaway would improve things -apparently they tend to be a bit rich as standard and can be leaned out by carefully filing away the cutaway in 1 mm steps as per dellorto or lessif cautious.What will also matter is that both slides are identical.
  Alternatively, lifting up the needle a notch and going down a size in idle jet might work it out.You might need all these changes ....suck it and see by doing one step at a time- leaving the slide mod last.
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