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77 Shovel fuel problem, S&S Carb

Discussion in 'Motorcycle Tech Talk' started by woojr, Jul 18, 2021.

  1. woojr

    woojr New Member

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    Hello & thanks for reading this thread. I have a 77 HD 1200 with SS carb, engine is pretty much like new, hasn't been ridden much in the last ten years. It has been kept clean in a garage and started and run around the back lot every summer. Last year I prepped it to sell. I removed the tanks, inspected and drained all the last drips of gas. Pulled the valve on tank and cleaned the intake screen.
    Installed new lines and a see through filter, disassembled the carb and inspected it. Everything looked fine including the float and setting. After putting the valve and lines on I put gas in it and opened the valve and drained the whole tank into a glass container. It flowed fast and the gas was clean. I attached it to the carb and turned the valve on but the gas flows slowly through the filter. It took awhile to fill the filter.
    When the fuel is full in the filter the engine starts right up. If I don't let it sit and fill completely, I can twist the throttle and see gas spray from the accelerator pump. But it doesn't start right up. It's starving for fuel to fill the bowl.
    I removed the bowl, its vented and the float seems right on. I blew through the in to the bowl with no push back at all.
    Something is keeping the bowl from filling. And this with the gas cap removed from the tank. I've had the carb apart twice, it's clean as a whistle.
    Last, it will fill and start easily if I wait ten minutes or so. I tried it without the filter and same result.
    I want to sell her but need to get this solved. Any ideas appreciated, thanks a lot for reading.

    John
  2. Red Rider

    Red Rider Well-Known Member

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    I had a similar problem years ago. It took forever to diagnose, but it turned out that the seal on the base of the gas cap was the problem. What would happen is the cap had deteriorated a bit (but not as much as you'd think - only a tiny bit) and so even though I'd completely cleaned the tank out and changed the lines, each time I put the cap back on a bit of the seal ring would fall in and re-clog the filter....though this may not be your problem.

    Did you check for a kink in the fuel line?

    Did you check flow from tank thru petcock, with or without filter, before it gets to carb?? Might still be gunk in the tank.

    Vacuum problem? I don't know S&S carbs

    Good luck!
  3. woojr

    woojr New Member

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    Thanks Red. It appears the needle valve slowly leaks through. I'm considering buying one of those cheap knockoffs and just see if it works better. If it does I'll rebuild the OEM carb. I've bought three cheap knockoff carbs for chainsaws & my 16 hp JD tractor. They all worked out of the box and were basically dirt cheap. How long the needles and other parts exposed to fuel lasts is anybody's guess. Hell, a rebuild kit ain't much less than the whole carb.
  4. hotroadking

    hotroadking Super Moderator Staff Member

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    Is it a gravity petcock or vac petcock.

    If vac and the line isn't connected, or it has a break/leak you can get poor flow.
    If Gravity you need to be sure the vac port on the carb is capped

    If gravity, it should flow out without restriction.

    Remove the filter, run a gas line to a cup, turn on petcock see if it flows better,
    if so hook to carb and see if it runs, might be the filters bad or backwards it should have an arrow on it for flow. Just things to check.
  5. woojr

    woojr New Member

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    It's gravity petcock, fuel flows 100% out open line. I leave the cap off for all tests.
    Clear filter shows low flow when running. If I open petcock before starting it fills really slowly. Then with filter showing half full and petcock closed, the level slowly goes down. It must be some issue with the needle/ seat assembly. I haven't had a chance to pull it apart until later today. I plan on that after it cools down later.
    I think there's something about the needle tip, the kit was probably an import cheapo.

    Thanks for all comments.
  6. hotroadking

    hotroadking Super Moderator Staff Member

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    Petcock should flow fuel until the bowl is full and the float/needle closes, then you'll see zero flow. Sounds like you could remove the carb, clean out all the bits, make sure the float is set properly, if it's too low you won't get enough fuel to run.
  7. woojr

    woojr New Member

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    Previously it appeared gas was leaking past the needle however, when I checked it this morning the gas level was exactly where I left it (in the fuel filter) last night. I'm letting it sit until tomorrow to make sure it holds. I will do as hotroadking suggests, open it up and check needle and float and setting.
  8. hotroadking

    hotroadking Super Moderator Staff Member

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    Since everything else seems to be working that's the only thing other than blocked jets. While you have it open blow out the main and idle jets, be sure everything is clean. And since it sat a while, if you haven't replaced the rubber fuel lines I'd do that too.

    Be sure the cap on vac tube on the carb is in good shape. Heat and time had caused a crack in mine, also ran a Pingle gravity petcock. It had idle and running issues because a small crack the rubber cap that had deteriorated causing a vac leak. its that black rubber cap at the top left of the image below.

    [​IMG]
  9. woojr

    woojr New Member

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    Finally had a moment to pull the bottom off the carb tonight. I found the float was set too high. Not sure how it changed over last winter but I'm going to examine it better with magnifier and bright light to see if something is failing (loose or cracked). Or if the needle tip has a fail. I'll post when I know more. Thanks for your interest.
  10. hotroadking

    hotroadking Super Moderator Staff Member

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    Let us know if it works, or not

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