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  1. #1
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Tuning low speed on a 1967 6hp

    I have replaced the ignition excluding the coils. Spark jumps a 1/4" gap nicely with a good snap. I have completely disassembled the carb and cleaned thoroughly paying close attention to the orfices and low speed circuit. I can not get it to run smoothly at a very low idle. I started with the slow speed needle backed out 1-1/2 turns,and it started on the first pull this morning at the lake after running in a barrel yesterday. I let it warm up for 4-5 minutes and trolled out to adjust the needle.The adjustments seemed to have no effect even after turning it in 1 full turn in,albeit at a speed which was to fast for trolling just to keep it alive.I ran it WOT for about 5 minutes and tried again.I had my timing light with me so I shot it and it fires just before the mark probably 3/32' before,exactly the same on both cyls. A couple things I noticed: the head never became the slightest bit warm and the water exiting the exaust relief port was not even slightly warm either.Also at mid throttle it was not quite as smooth as WOT or low idle(as low as I could get anyway). Timing was the same at all speeds. I am confident in the ignition work and the carb work,if the Tstat was missing or stuck open would that affect the low speed tuning? Thanks ,I know its a long post but wanted to provide as much info as possible.-B
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  2. #2
    Join Date
    Feb 2001
    Location
    Central West Florida
    Posts
    14,120

    Default Re: Tuning low speed on a 1967 6hp

    This post sounds familiar.........

    Make sure the high speed jet located horizontally in the bottom center portion sof the float chamber is absolutely clean.

    Make sure that you have installed the thick cork gasket on the center vertical brass nozzle.

    For better or worse, the adjustments of the top adjustable slow speed need le valve should make a difference in the rpm setting as you adjust it.

    (Carburetor Adjustment - Single S/S Adjustable Needle Valve)
    (J. Reeves)

    Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

    Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

    Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

    When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
    We occasionally have questions. If you fail to answer, it may affect ours.

  3. #3
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Re: Tuning low speed on a 1967 6hp

    Yes I am sure that these things are correct Joe,but it is as I described. If you say to recheck my carb work I will,but I am sure I did the above.-B
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  4. #4
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,767

    Default Re: Tuning low speed on a 1967 6hp

    Very common for the thermostat to be stuck open.---Yes I see that often on these !

  5. #5
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Re: Tuning low speed on a 1967 6hp

    Racer,would that have any effect on low speed operation?
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  6. #6
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,767

    Default Re: Tuning low speed on a 1967 6hp

    ???----I would think so.---But everybody has different ideas on how these wonderfull motors should run.----I have a bunch of them.----One being a 67 mpdel.----Of it does not respond to the low speed needle you missed something in the carburetor work !

  7. #7
    Join Date
    Feb 2001
    Location
    Central West Florida
    Posts
    14,120

    Default Re: Tuning low speed on a 1967 6hp

    (Point Setting Of Magneto Models)
    (J. Reeves)

    Set the points as follows. Have the flywheel key aligned with the fiber rubbing portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

    NOTE 1: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

    NOTE 2: Should the cam have the word TOP embossed on the top of it, that is a cam that could be installed upside down and this is simply telling you which side is up. It is not a position where one would set the points.
    We occasionally have questions. If you fail to answer, it may affect ours.

  8. #8
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Re: Tuning low speed on a 1967 6hp

    I set the points with a meter,I just prefer to do it that way.So here is where I went wrong: When I installed the needle I had inserted the packing first,and when I screwed in the needle the resistance created by the packing made me think that the needle was seated and it was not close to being so. I took the bowl off and checked all that was mentioned above and it was good,I was about to ask yall about reed valves. I reassembled and noticed that the needle didn't screw in very far until seated. Then I removed the packing and counted the total turns until seated,about 14 1/2. I probably had it in 6 or 7.As much as I wanted to turn the needle in more,I did not want to make it too tight and damage it,so lesson learned on seating a needle.Only my second carb job.I tanked her and she runs beautifully!It idles down a little past where the roller leaves space between the cam. Too bad I didn't have it dialed in for fishing this morning,but I still managed 3 Rainbows in 30min with it running crappily. Thanks fellas,I know I ask a lot of questions but I will be the one answering them someday.
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  9. #9
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Re: Tuning low speed on a 1967 6hp

    So I fished it today,and it ran really good at low speed,however every once in a while(5 times) in three hours it would die but not like fuel starved die,no bump in idle before caput,just idle lower and lower to stop. Restarted every time with choke. I am confident that the stat is stuck open as the head never became warm and I think this is my issue that it is not warming up. I will change the stat but do yall think this is the the problem? Me and my kids got into the fish bigtime,double headers all morning!
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  10. #10
    Join Date
    May 2014
    Location
    Reno
    Posts
    252

    Default Re: Tuning low speed on a 1967 6hp

    Update.Changed out the stat and it runs noticeably better.
    84 Beachcraft 3.8 229cid 6681735 R drive6683545

  11. #11
    Join Date
    Nov 2011
    Posts
    1,550

    Default Re: Tuning low speed on a 1967 6hp

    Yep, shows that the little things do matter.

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