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Thread: Atmospheric valve on early motor

  1. #1
    Join Date
    Dec 2010
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    Lamoille County, Vermont
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    Default Atmospheric valve on early motor

    Got a question about an atmospheric valve. Friend of mine has one of the Timeless bikes like mine and we've been working on getting it running. It starts right up, runs great, but after about 30 seconds appears to starve for fuel then quit.

    We have great gravity fuel pressure and the bowl is staying full. The spark is hot right up to the end. No issues there. Engine is free and turns nicely even after it quits. No seizing at the piston or bearings.

    My current theory is that the atmospheric intake valve may be a bit tight in its guide. When it gets hot, it is hanging up enough to kill compression and stop the motor... in a way that appears to be fuel starvation.

    When cold, the valve seems fine. I have not yet measured the clearances. Does anyone have a specific clearance for an atmospheric valve in its guide? This should be the same spec and the 1909 - 1913 Harley motors as that is what the folks at Timeless copied. Should there be any lubricant up in the valve guide?

    Any thoughts from you guys who have more experience with atmospheric valves?

    Cheers

    Sirhr
    Last edited by sirhrmechanic; 12-11-2012 at 05:41 PM. Reason: clarify

  2. #2
    Join Date
    Feb 2007
    Location
    Headingley Manitoba Canada
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    402

    Default

    If you are running a timeless with their carb it maybe the problem. I would change the carb and I think you'll find it will run fine. It will leak however. Dick Orloff (yellow spear fame) is the guru on upgrading a timeless to be a dependable runner.
    Ross

  3. #3
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    Default

    Hi Ross: The original carb was the first thing to go. It's on a shelf looking pretty. I built a new manifold and we adapted a Linkert from a WL/Servi to the engine. You can see how we did it here on the forum as I posted a pile of pictures of mine while I was adding a magneto...

    One of the things we may try is swapping on the Linkert from my bike because it works well. But before we do that... I was curious about the possibility of the valve being the problem. Every indication we have is that the Linkert (which is rebuilt and seems to be in perfect shape) is doing its job. The bike cracks right to life an runs like it wants to. But after about 30 seconds, dies. We checked fuel flow. Made sure that the fuel line was not mounted so it trapped an air lock in it... it was fine. The gravity feed dumps plenty of fuel in -- more than enough to keep up with the motor so we're not draining the bowl.

    I'll see if I can get Dick's input. Thanks for the lead and I appreciate your time!

    Cheers,

    Pierce

  4. #4
    Join Date
    Jan 2007
    Location
    Corvallis, Oregon USA
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    Default

    Would be easy to try a little oil on the valve/valve guide?
    Bill Gilbert in Oregon

  5. #5
    Join Date
    Feb 2007
    Location
    Headingley Manitoba Canada
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    Default

    I know this is elementary but is the gas cap drilled.?
    Ross

  6. #6
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    Default

    Ross. First thing I did when we started working on the bike. Because it's not drilled as it comes from Timeless. Hole is plenty large. We have great flow into the carb.

    We are going to pull off the valve both to see if it's tight in the guide or if it has some rust or a burr. And we'll lubricate at the same time.

    Bike is really 'trying' to run. Wants to go and sounds like it 'really' wants to go. I think it will be a great motor...

    Cheers,

    Sirhr

  7. #7
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    Feb 2007
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    I would be interested in the outcome of your tinkering.
    Ross

  8. #8
    Join Date
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    Thanks for the good thoughts, Ross. I'll definitely keep you in the loop.

    If you didn't see it, here's the 'tinkering' thread from before. This is my bike, which I converted to Magneto and M16 Linkert.

    http://www.antiquemotorcycle.org/bbo...-Magneto-Drive

    Cheers,

    Sirhr

  9. #9
    Join Date
    Dec 2006
    Posts
    1,276

    Default

    try lard with graphite powder on the valve and guide. the lard will burn off but the powder will stay. i guy told me about doing this to an anzani 8 valve. and how this treatment made it sound run like a whole different motor.

  10. #10
    Join Date
    Feb 2003
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    High in the B.C. Rockies....
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    5,353

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    I wonder if it's a spring tension issue???

    Cory Othen
    Membership#10953

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