8 HP Techumseh Starting Problems - need Help - Pictures

Discussion in 'Mechanic and Repair' started by 1966vette, Jun 12, 2010.

  1. 1966vette

    1966vette LawnSite Member
    Messages: 209

    Tecumseh Engine owners!

    I purchased a lightly used MTD Chipper with 8 HP Tecumseh Engine Model # HM80-155426M, Carburetor 632351, earlier in the week for $120.

    During the Chipper demo the engine demonstrated difficulty starting & the previous owner explain the engine does not have compression starting release.

    It takes much effort to pull start an 8 HP engine w/o compression release.
    I pulled the spark plug & it was load with carbon / un-burnt gas which indicates it has been running much too rich.

    When I got the Chipper home & I installed a new spark plug & rebuild the carburetor.

    I adjusted the high speed air / fuel mixture valve & wide open throttle & the engine runs smooth.

    I also adjusted the idle speed air / fuel mixture valve @ low idle & the engine runs smooth.

    Starting fluid is always required to start the engine under any conditions.
    What is the deal with this carburetor?

    Could my problem be that the 8 HP engine is difficult to pull start because it turn over slowly?

    Also, It is normal for the chipper to vibrate like washing machine out of balance?

    Any advice will be much appreciated.






  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Most direct drive chippers can be a bear to pull over because of the heavy blade disk, They also have some vibration but shouldn't be that bad.

    These carbs have a small often missed port in the bowl nut that doesn't get cleaned out, There is also a port with a tiny check ball inside ("HERE" below) that can't be accessed for cleaning and soaking for a month has no effect. Once this check ball sticks the carb will not function properly.


    How many turns open do you have the low and high speed adjusters ?
  3. Ruben Rocha

    Ruben Rocha LawnSite Senior Member
    Messages: 577

    I have the same type of jet bolt.
    Let me tell you the hole is very very small.
    And I mean you may need some reading glasses to see it.
    I usually strip a twist tie from a loaf of bread to clean it out.

    Did I say the hole is very small.

    But if the hole is stopped up it will not start.
    It may fire but will not run.
  4. 1966vette

    1966vette LawnSite Member
    Messages: 209

    High speed adjuster is 7/8 of a turn out
    Low speed adjuster is 3/4 of a turn out

    The 7/8 high speed adjuster was set at WOT & achieved a smooth revving high RPM engine.

    However, went from idle to WOT a small amount of gas sprayed out of the air horn as the air filer was not on for these adjustments.

    If I open the high speed adjuster to achieve acceptable acceleration the engine does not run at max speed.

    I have been told that once this type of carb gets gummed up it is extremely difficult to get overhauled properly.

    Please share your thoughts.
    Thanks for helping!
  5. 1966vette

    1966vette LawnSite Member
    Messages: 209

    Is this jet indicated in the picture above?

    Thanks for helping!

  6. Ruben Rocha

    Ruben Rocha LawnSite Senior Member
    Messages: 577

    Yes it is.
    Restrorob indicated two points to check.
    One is the bolt he is holding in his hand with a piece of wire stuck in it.
    Showing where the hole is
    That is what I was referencing.
    The other is the port on the carb with the check ball.
    Which the red arrow is pointing to.
  7. ronmowers

    ronmowers LawnSite Member
    Messages: 23

  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    3/4 and 7/8 is running leaner than normal, Most are in the 1 to 1 1/4 low and 1 1/2 to 2 on the high. Checking/cleaning the small port in the side of the bowl nut may help a little but the check ball is likely stuck.

    I quit trying to rebuild Tecumseh carbs years ago just because of the check ball, Spending $65 to rebuild verses $65/$75 for a new carb guaranteed to work properly makes more sense.
  9. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Ron, This is a Tecumseh valve in block engine. Most all "L" head engines don't require periodic adjustments, This is a direct drive (no pulleys/bearings) unit which is hard to pull due to the weight of the chipper wheel. If the carb is right it will start with the slower pull. [​IMG]
  10. 1966vette

    1966vette LawnSite Member
    Messages: 209


    If I remove the carb & shake it, should I hear the check ball rattle?

    No check ball rattle indicates the carb will never perform as new.

    The check ball can't be repair & the carb is junk?

    Thus, I have 2 options:

    1. Have starting fluid always available when chipping

    2. Purchase a new carburetor and hope it resolves the problem.
    Does the new carb require adjustments?
    The adjustments are easy if the carb function properly.

    Thanks Again!

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