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Thread: Rough running Scout 800

  1. #1
    Join Date
    May 2009
    Posts
    16

    Default Rough running Scout 800

    Ok, I have a 1970 800. When I start it at full choke it does not idle very high. Then when I dial it down to half choke, motor sounds weak. Then I push choke all the way in and step on gas and it stalls. Did I fould the plugs?? Thanks

  2. #2
    Join Date
    Jun 2009
    Location
    Hurlburt Field, FL
    Posts
    495

    Default

    What size engine? It kinda sounds like a bad fuel/air mixture, but it never hurts to check the simple stuff like spark plugs and wires.

  3. #3
    Join Date
    May 2009
    Posts
    16

    Default 304 Motor

    So it could be carb?

  4. #4
    Join Date
    Jun 2009
    Location
    Hurlburt Field, FL
    Posts
    495

    Default

    Could be. Could be a couple of other things. What kind of engine do you have? It helps to know what we're talking about here.
    Last edited by lindstromjd; 07-17-2009 at 11:00 AM.

  5. #5
    Join Date
    May 2009
    Posts
    16

    Default Rough Runnin Scout

    It has the 304 with the auto Borg Warner tranny. Thanks

  6. #6
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    Quote Originally Posted by afewing View Post
    Ok, I have a 1970 800. When I start it at full choke it does not idle very high. Then when I dial it down to half choke, motor sounds weak. Then I push choke all the way in and step on gas and it stalls. Did I fould the plugs?? Thanks
    If it starts, the plugs are still okay.

    Start with closed choke. After it catches, do not assume "half choke" is correct. Every carb has a sweet spot for the manual choke. Open and adjust for best cold idle. On my travelall, it's almost all the way in, about 3/8" from the dash. That's where I warm it up.

    Once it's warmed up enough, you need to push it in, let it run, and adjust the idle... and the timing... and the mixture... etc.

    If you open up the choke too early, the engine will bog down and stall. If you're doing this to a cold engine, forget it. Even in the summer it still takes a little time to warm up a 40 year old engine.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  7. #7
    Join Date
    May 2009
    Posts
    16

    Default Running Rough

    Seems to be worst at stop to start, like pulling out of the driveway or stopped at a light.

  8. #8
    Join Date
    Jun 2009
    Location
    Maryland
    Posts
    145

    Default warm up issues

    I am assuming a Holley 2300 275 or 350 cfm carb.

    If after checking your timing, ensuring you do not have a vacuum leak, and have unfouled plugs, you will need to dial in the fuel/air settings on your carb. If these are all OK, you have a blown power valve and/or a severely worn accellerator pump cam. The accellerator pump cam is the nylon piece attached to the accellerator arm on your carb linkage. It faces the body of the carb. If the carb pops or backfires on accelleration from a stop and you have checked for the vacuum leak and acc. pump cam, you will need to replace your power valve.

    I would also recommend the thick fiber spacer/gasket between the carb and the intake. It is better than the thin gasket for sealing vacuum leaks and for heat insulation once the engine is hot.

    I would also recommend an inline fuel filter if you do not already have one or replace it if you do. Might be a good idea to work from a clean source of gas like an outboard motor tank.

  9. #9
    Join Date
    May 2009
    Posts
    16

    Default Rough Running 800

    I think the vacuum leak is the issue. How do I find it?

  10. #10
    Join Date
    Jun 2009
    Location
    Maryland
    Posts
    145

    Default vacuum leak

    First make sure your base timing, dwell and point gap are all good. Make sure the distributor hold down is tight after timing (ask me why I say that)
    If you suspect a vacuum leak, you can spray WD or carb cleaner near the carb base (not in the carb) and if it speeds up that is where your leak is.

    You can also slowly put cupped hands over the carb (careful not to let your tie get caught in the fan) closing it off and if it briefly speeds up before dying or just keeps running unaffected it would indicate a very bad leak somewhere. If it just dies out it is unlikely you have a vacuum leak. Running strong on a fully or mostly choked carb after warm-up is another indication of a significant vacuum leak.

    Make sure any unused vacuum lines or ports are capped. Examine your vacuum advance line at your distributor to make sure it is properly connected and there is no physical damage to it. Make sure the four bolts that hold the carb to the manifold are tight. Do not overtorque them. Is your base gasket torn? It can happen if you remove/reinstall the carb repeatedly.

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