The 101 Association, Inc.
For the preservation and enjoyment of 1928 to 1931 Indian Scout Motocycles
"You can't wear out an Indian Scout"

Gas pouring out of carbureter

  • 26 Apr 2017 11:22 AM
    Message # 4781259

    So I finally got my scout ready to run. It started first time but when running gas pours out the carb and its choked down by being to rich. I had paid a carb guy recommended on this forum to rebuild it but when I inspected it the needle arm was really sloppy and the needle was still the old worn one. So I purchased a new needle tightened and honed the needle arm put in a new COTTEN float but the symptoms are exactly the same. I am 100% sure the float is working correctly and no fuel leaks out when not running but when running fuel spits out the carburetor all over my knee. Any ideas anyone? 

  • 27 Apr 2017 3:32 AM
    Reply # 4786288 on 4781259

    Hello Peter,

    I just got my bike ready and running. So this is a work in progress. I had exactly the same problem. It took loads and loads of messing about to get the float height right and the needle valve to seal when the float bowl is full. I was told that it is very important to get the top little button of the needle moving really freely in the little fork on the float leaver. I took it out and polished it and tweaked it so many times. An long experienced Indian guy told me this is the only way!

    I have the mixture about right now. So float height is okay. The sealing on the needle is okay while the bike is running, but if I leave the fuel on with the bike stopped the fuel slowly fills the bowl and overflows. So when I start the bike I turn the fuel on and let the bowl fill then turn the fuel off. Once the engine starts I turn the fuel on again, Also I make sure I turn off the fuel as soon as I stop the bike and it's okay. 

    Cheers, Jon

  • 27 Apr 2017 3:38 AM
    Reply # 4786292 on 4781259


    I remembered I did / do have problems with the float sticking down after the bike has been stood for a long time and the fuel has evaporated out of the bowl. So if the bike has been stood I take out the plug that is on top of the needle valve and as the bowl fills for the first time I "tickle" the top of the needle with a little screwdriver to make sure it isn't stuck.

    Also I do the same when I re-fit the bowl onto the carburetor to make sure the float doesn't catch and stick.

    Cheers again Jon

  • 27 Apr 2017 4:48 AM
    Reply # 4786597 on 4781259

    Sad to hear that you have had several issues with your restoration!

    refurbished carb to factory specifications should not dribble!

    Was the old needle cone ground and polished to mirror finish? It should be ground to somewhere 30-45 deg, but the angle is not overly important, if the needle is used to form the seat. In that case you should perhaps save and use it because in some cases the orig needle is lighter than a reproduction. 

    Is the needle seat thin? I like mine to be about 0,4mm/.015in when refurbished, in order to seat easy and be less sensitive to side loads that can knock it out of alignment. And I always burnish the seat only with hand pressure, never tapping. Never ever in any case I got a seat tight with any grinding compound. Even tried toothpaste but that is useless, doing absolutely nothing. 

    The needle arm needs a fine fitting on it's pin. A sloppy twist- and side-to-side fit and the needle is easily knocked out of alignment to the seat.

    Most people think that a wider seat will be tighter, but in fact it is the opposite if the force that the float is exerting upon the needle is the same. The force per square mm or In. is higher the thinner the seat is. A larger surface area does not seal better, on the contrary, the force per area unit lessens and makes it easier for the fluid to pass. Because of the fluid viscosity of the petrol, and imperfections in the valve, alignment and wear resistance, the seat however might need to be broader than just knife edge thin.

    Last modified: 27 Apr 2017 6:42 AM | Carl-Erik Renquist
  • 27 Apr 2017 6:41 AM
    Reply # 4786739 on 4781259
    Tim Raindle (Administrator)

    Hey Pete, old trick for Amals, use cigarette ash as a very fine lapping compound. Can take a while to get angles etc correct, even then, when on a sidestand will probably still leak. Make sure the angle of the needle is not too great, as above, if the forks on a Linkert or the nut on a sshebler are snagging the top of the needle and it doesn't move freely it will not seat straight. 

    I just turned a float upside down on a bike to see if I could get it to lift better, seems to work so far. Hollow cell one. Check clearance on float too, make sure its not snagging on the bowl and sticking. 

  • 14 May 2017 4:11 PM
    Reply # 4832969 on 4781259

    Most importantly, one needs to visualise the float working in situ, before it is affixed to the carb body !  Floats float, so with the carb bowl detached, observe it floating whilst adding fuel directly to the bowl.  It may act like a 'sinker' and stay on the bottom, or it may have partial bouyancy.  You may also sight any restrictive contact, that the float may have, with the bowl side.  Observe the bowl for sometime, for leaks, in and around the needle seat area.  Float height, as mentioned is important.  It measures 7/16" from the bowl's top rim, to float, once fully floated by fuel.  Hope this helps.  A bung or finger may be used to plug the bowl hole before filling.

  • 15 May 2017 9:57 AM
    Reply # 4834426 on 4781259

    By some miracle my 101 carb works most of the time sttting or running.

    In the distant past I recall that rubber-tipped needles were available in the rebuild kits for some carbs and that they seemed to never leak.  Does anyone make them for these antique carbs?  Of course the rubber would need to be ethanol resistant these days....................

  • 16 May 2017 8:13 AM
    Reply # 4835965 on 4781259

    Mine suffered from exactly this issue.  The root cause turned out to be the needle seat was loose in the carb. casting, allowing fuel past the needle/seat joint, even when the needle was a perfect match to the seat.

    I carefully tapped the seat back into the casting, and have seen no more leaks to date. 

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