runs hot and dark smoke

Discussion in 'Mechanic and Repair' started by jasonjonesboro, Mar 17, 2006.

  1. jasonjonesboro

    jasonjonesboro LawnSite Member
    Messages: 1

    Its a Tecumseh 8 horse commercial just put used carb (from the cleaned up junk pile) I have never adjusted carbs before but it acts like it is getting too much air and gas at the same time, exhaust is really hot and blows dark smoke at the same time???? I've adjusted the needle on the bowl bottom and the air flow from nothing till it won't run and can't get it to smooth out.:confused:
  2. Smalltimer1

    Smalltimer1 LawnSite Bronze Member
    Messages: 1,223

    Tecumsehs can behave strangely like that. But from your description it sounds like it's burning rich. You'll need to tune the screw on the side of the carb in until it smoothes out and the smoke goes away and there is no missing/skipping. If a series of adjustments doesn't work, then you'll probably need to look for a carburetor in better shape.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Try this, Take the adjuster on the side which is the low speed and turn it in all the way then back it out 1 1/2 turns. Take the adjuster on the bottom of the bowl which is the high speed and turn it in all the way then back it out 2 turns. This will be a starting point, Start the engine and let warm a few minutes just above idle. When warm idle engine down then adjust the low speed either in or out slowly until you get the smoothest idle. Now give the engine full throttle and perform the same procedure on the high speed adjuster unit it runs smooth.
    If when adjusting from this starting point then engine idles or runs erratically then look for a new carb. , There is a check valve in these carbs. that can not be gotten to for cleaning so it must be replaced to have the engine perform correctly.

    Good Luck

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