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Amateur Manx 40M preparation

This is a discussion on Amateur Manx 40M preparation within the Vintage Motorcycle Racing forums, part of the Caferacer.net Forums category; Originally Posted by Mike 40M Emptied the fuel tank. According to my calculations, she used 1.5 miles per gallon! My guess today is that the ...

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Thread: Amateur Manx 40M preparation

  1. #91
    Senior Member Cyorg's Avatar
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    Quote Originally Posted by Mike 40M View Post
    Emptied the fuel tank. According to my calculations, she used 1.5 miles per gallon! My guess today is that the problem is something with the float chamber.
    Paragraph 3 in post 81?
    "Non urinat in ventum"

  2. #92
    Senior Member Mike 40M's Avatar
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    Might very well be that Steve is right.......AGAIN
    Will play a bit with the present float chamber a couple of days before ordering a matchbox.
    Still some time before Brexit, until then easy to get parts from UK. After that no one knows.

  3. #93
    Senior Member jalsteve's Avatar
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    If the float chamber is good and doesn’t flood - set the fuel height so that a 1/3 throttle opening the fuel gushes out of the fuel jet.

    It’s sound as though you bike is running the fuel low in the float then the engine starves and dies. You need a big bore fuel tap too. Make sure the fuel free flows out of the float chamber and that the tank is breathing properly.

    You can realease the vernier back plate from the magneto shaft and time traditionally.

    What’s the plug colour sooty?
    Lite the blue touch paper and stand well back!

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  5. #94
    Senior Member Mike 40M's Avatar
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    I'm quite certain that fuel flow to the float chamber is adequate. Will doublecheck it though. Tap is same as it had before, so I believe it will suffice.
    Plug a bit sooty.
    The difference between the GP and the Gardner is that on the GP there is a short rubber tube between carb and float. On the Gardner the tube is longer as it has to move up and down.
    My present guess is that the float chamber now can swing easier to and fro. At higher revs it will vibrate so much that the fuel overflows and goes out of the top vent. I have seen this happen on a Velocette KTT with AMAL Matchbox float chamber.

  6. #95
    Senior Member jalsteve's Avatar
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    Does the fuel flood out of the fuel jet a 1/3 opening?

    Float chambers flopping about is a problem and the resulting fuel frothing. The only fixed points you have is the anti vibration mount and fuel tap, fit some copper pipe say 8mm bore inside the feed line and bend to shape. Clamp as normal leaving about an inch on tube either end the copper tube will help stop the float moving too much. On tradition gp set up I fit copper tube in the pipe from float to carb banjo.
    Lite the blue touch paper and stand well back!

  7. #96
    Senior Member jalsteve's Avatar
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    I should have said - don’t use braided fuel line you must use something that stays flexible from the float to the carb bottom feed. The sort of hose used by Japanese manufactures is perfect. Many fuel lines go hard quite quickly which isn’t much help for the carb feed line but can help holding the float still. Every cloud.........
    Lite the blue touch paper and stand well back!

  8. #97
    Senior Member Mike 40M's Avatar
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    As season comes closer, time to do some preparations on the 350. I did some experiments with the Gardner and an AMAL Matchbox float bowls. I believe that the Gardner is more sensitive to vibrations than the Matchbox. To be able to return to the Gardner, I made new mounting parts for the Matchbox. For adjusting fuel height. I used a supershort circuit tank, took it from a scrap vibro plate. Gave much better work space. So a test start next.
    Name:  Very short circuit tank.jpg
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  9. #98
    Senior Member grandpaul's Avatar
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    You're going to have to pick up momentum!

    Nice bike.
    GrandPaul
    Author, \"Old Bikes\"

  10. #99
    Senior Member Mike 40M's Avatar
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    Test start accomplished. It'a a lovely engine (thanks Molnar), really smooth. Only air in tyres and petrol in tank (not the opposite). It's a very easy starting machine. As an old racer explained it, compression ratio should be where it gives lot of power and is easy to start. In the old days when engine was off when the flag was dropped. Seems the float bowl change worked. Now load everything in the van. Practise on track sunday.
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    TrialsRider and CaTacL1sm like this.

  11. #100
    Senior Member TrialsRider's Avatar
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    That bike is so nice it's sic.

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