Buy Johnson Outboard Parts

Announcement

Collapse
No announcement yet.

1992 120 johnson air problems

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 1992 120 johnson air problems

    I have a 120 johnson with throttle bodies that runs great without the air box but will not plain with the air box on. I've set timing with a light, took carbs apart and checked, and looked for ways that exhaust may be leaking under the calan. I'm at a loss. Anyone with any ideas could help .

  • #2
    I don't have the answer to your problem... BUT... it's strange because usually the problem you're encountering is just the opposite of your explanation. That is, the engine will not run properly with the air box removed.

    Normally the air box is required as it is a air restriction of sorts, needed to richen the flow of fuel through the carburetors.

    Have you changed carburetors or installed different jets? Apparently the air box is causing your engine to run too rich with it installed?

    What work, if any, has been performed recently?

    Comment


    • #3
      I put kits in carbs last year and done ok but always wanted to smoother until it plained out. Over the course of a year, its just got worse til it want plain. I've worked on a lot of these throttle body motors but never came across this. It is like it has to big of jets or to small of air box. Possible someone changed something on it before me. Just a trial and error thing. Bout ready to brake out the drill and add some air to the box.

      Comment


      • #4
        I can't get at my books right now but in the morning I'll check to see what size jets are supposed to be in those carburetors.

        The bad part of the story is that you indicate that over the coarse of a year the problem got worse... and for something to get worse with nothing being done to it to make it worse... well, that's not a good thing.

        Take a compression check when you have time. What are the psi readings of the individual cylinders?

        Check to see that all throttle butterflies open and close at the same time. The butterflies should just start to open when the cam scribe mark is dead center with the throttle roller.

        The throttle roller should be approximately 3/8" in diameter. It used to be that the roller was all one piece but some idiot decided to make it a two piece unit which is a small black roller (approx 1/8") with a larger clear covering to bring it up to the 3/8" diameter. As usual, a big mistake... the clear covering is junk and eventually breaks away, leaving the smaller roller and of course throwing the synchronization off completely. Bottom line... check the roller for the proper diameter.

        Comment


        • #5
          Okay, next day.... 1992 120hp Johnson.

          Of course I have no idea if a previous owner might have installed improper carburetors (higher hp?) or not (check with him/her), but as far as the jets are concerned, the following is what is supposed to be in those carburetors.

          Intermediate Air Bleed (Top jet) --- 323708 - #50 (.050 ID)
          Slow Speed Air Bleed (Bottom jet) - 328535 - #41 (.041 ID)

          High Speed Fuel Bleed - 328544 - #63D - (.063 ID)

          Let us know what you find.

          Comment

          Working...
          X