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Thread: Duclos Hit and Miss Engine

  1. #1
    Join Date
    Nov 2004
    Posts
    7

    Question Duclos Hit and Miss Engine

    Greetings Everyone,

    Once again I need the expertise of the Home Machinist community. I just finished building the Philip Duclos Odds ‘n Ends Hit ‘n Miss Engine, (it took about a year on and off). However, I’m having a hard time keeping it running. Initially I am using stronger springs on the governor so that it would not engage just until I got the engine running well, but it seems I’m having a problem with the mixer, (carburetor). I tried using both Coleman Fuel and gasoline and the result is the same. I open the needle valve about ¼ to 1/2 turn and spin the flywheel while holding my thumb over the intake until I get a pop from the exhaust. Next I give the flywheel a brisk spin with the intake open and the engine will fire anywhere from 6 to 10 revolutions then stop. If I try opening the needle valve on the mixer (carburetor) a little each time I spin the flywheel sometime the engine will fire and sometime it will not. If I open the needle valve too much, (usually more than a turn) I get a strong odor of fuel as well as raw fuel coming out of the exhaust port. The needle valve has a 75-degree angle and the inlet diameter of the mixer is a #60 drill (.040” diameter) as per Mr. Duclos’s blueprint specs. I am using a NOS Pontiac Coil Company Buzz coil, a 6-volt battery and a HONDA spark plug. The “Buzz Box” throws one hell of a spark even on a 6-volt diet. I think my problem lies with the fuel/air mixture but any help might keep consulting my other friends, Jack Daniels and Jim Beam, not that’s a bad thing J. Thanks in advance and Merry Christmas!

    Regards,
    Robert (Bob) Cvarovsky

  2. #2
    Join Date
    Jul 2003
    Posts
    480

    Post

    I'm no expert but try putting the tank at the same height as the carb. The first time I started my Bob Shores Eagle, the tank was 2" or so below the carb. Ran about like yours, 12 pops or so and that was it. Then I raised the tank c/l to the carb c/l and fixed the problem.

    Also tried a check valve in the fuel line... Never did work as well as simply raising the tank.

    Now, with the engine off if the tank is full it will drain thru the carb so I had to provide a shut off valve.

  3. #3
    Join Date
    Aug 2005
    Location
    Indiana
    Posts
    44

    Post

    Hi,

    Someone posted here recently with the same problem. Maybe try some of the suggestions offered there:

    http://bbs.homeshopmachinist.net//Fo...ML/002287.html

    Hitnmiss is right about the fuel tank level. This type of carb will draw fuel a short distance, but not too far. I designed mine so that the highest level in the tank was around .25" below the bottom of the carb. That way gas won't siphon out thru the carb, but it still doesn't have to lift the gasoline very high.

    I have found this type of carburetor very forgiving, as long as you've got good compression and a hot spark.

  4. #4
    Join Date
    Oct 2005
    Location
    Lower SE Michigan, USA
    Posts
    1,281

    Post

    Is there a check valve in the fuel line anyplace? Most H&M engines that use suction to get gas to the carb have one, usually in the pickup in the tank. If your engine has a check ball, it's probably leaking; lapping it might help.

    If there isn't a checkball someplace, there probably SHOULD be.

  5. #5
    Join Date
    Nov 2001
    Location
    Toledo, Ohio
    Posts
    9,030

    Post

    It has been several years since I built that engine, and it was traded for partial payment on a milling machine.

    I do remember having to play around with the level of the fuel tank to hit a happy medium between running and flooding.

    Since then, I built the Fairbanks Eclipse Vertical engine and a modification recommended by other builders was to reduce the diameter of the carburetor venturi area. I wonder if that would help these engines lift the fuel better as well.
    Jim H.

  6. #6
    Join Date
    Aug 2005
    Location
    shreveport La
    Posts
    2,674

    Post

    Tipical engine stuff .Most of duclos engines work better with check valve in gas tank .Try raising or lowering tank also turn your needle valve down some . If you turn the needle valve closed and try to start it after it stop`s an it trys to run it is getting to much gas. check out my engine site www.cp-tel.net/mary/mary-index.htm


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