Yamaha carb adjustment instructions?

Discussion in 'Outboard Maintenance' started by Dillusion, Apr 29, 2013.

  1. Dillusion

    Dillusion devilray snob

    So I got this here 50hp 2 stroke yammy...I have both the owners manual and the service manual. But neither tells you how to 'adjust' the carbs like the mercury manual does.

    The service manual tells you how to remove the carbs and re-install them, and shows you an exploded parts diagram...I found the chart with the float height and etc...but for the life of me I can't find where it says my idle adjustment screw and my carb needles should be adjusted at...IE- '1.5 turns out from lightly seated'. The merc manual for my old outboard says this in plain english, yamaha, not so much.

    I have a carb kit coming this week for all three carbs as well as a new fuel pump, fuel filter, and fuel enrichment gaskets/diaphragm...but when I put it back together, it doesn't tell me how to adjust that silver carb needle inside of each carb? or the pilot screw on the side of the carb under the cap?
  2. cutrunner

    cutrunner Cert. Yamaha technician

    The cap is the epa not wanting you to adjust idle mixture.
    And you shouldnt have too.
    Just clean the carbs and put it back togther as it was and it should be good to go.

  3. Dillusion

    Dillusion devilray snob

    Ok, so the silver needle should just be lightly seated? How many turns out for the idle screw?

    PS- the motor is not starting right now if the emergency fuel enrichment is set to normal...so I'm replacing all this stuff. The carb bowls were dirty on the bottom so something is clogged up. With the emergency enrichment set to 'on' the motor turns on, but stalls out and misfires and runs like chit.
  4. cutrunner

    cutrunner Cert. Yamaha technician

    You dont need to adjust anything imo.
    Your problem is it has 10 hours on it then it sat and I would bet money on at least one of your idle jets (tiny) are clogged causing the hard start.
    Trust me
  5. Dillusion

    Dillusion devilray snob

    I'm with you, I completely agree something is clogged- that's why I'm rebuilding the entire fuel system from the QD to the carbs....I'm just used to merc carbs, that's all.

    I know there's a silver needle valve in there and didnt know if it needed to be seated all the way or not- I guess I just seat it lightly and leave it!
  6. MariettaMike

    MariettaMike Wish'n I was Fish'n!

    I cleaned mine a while back and was told by a Yamaha mechanic who looked it up in a book he had to set the idle mixture needle valves at 1-1/2 turns from seated as a starting point and adjust from there. That worked and I didn't touch them. (I have a 90)

    The only other adjustement was idle speed located on the throtlle linkage of one carb. I did lower my idle speed.

    I just cleaned under the cap by squirting carb cleaner through the hole with an infant nasal aspirator and then air. I did the same with all the other parts and it worked out fine.


  7. cutrunner

    cutrunner Cert. Yamaha technician

    Your right it does have a needle, and seat like any other carb I just cant understand what you mean by you cant find it?
    Sorry im not following you
  8. Dillusion

    Dillusion devilray snob

    Mine doesnt have that black rubber cap next to the main jet, I have a silver needle valve that screws down. Which of those was your idle mixture needle?

    My silver needle vale has no spring to put tension on it if it's loosened....
  9. cutrunner

    cutrunner Cert. Yamaha technician

    You really are losing me matty.
    I thought about it and im pretty sure ive never done a 50. I have done 60, 70, 90 40, 25blah blah.
    Anyways I checked the microfisch just to be sure and its almost exactly like the 90.
    Fwiw I looked up a 2005..
  10. Creek Runner

    Creek Runner Well-Known Member

    I'm just not going to say it, same thing we went through with setting the timing on his Merc. Everyone wants to be a boat Mechanic. Those carbs are simple, I can have them off, cleaned, back on and running in an hour. Take it to a shop!

    Also didn't in the other post you tell me that the carbs were just rebuilt by a Yamaha dealer, as I told you the carbs would need to be gone through due to the lack of use.

    Also those pictures don't show the air/fuel mixture screw (not called idle mix screw) the air/fuel mixture screw is located on the outside of the carb just like every other 2 stroke outboard carb in the world!
  11. AfterHours2

    AfterHours2 Stripper in my own Mind!

    Not to confuse things anymore than they already are but which type of screw is located under the brass factory plug that has to be drilled out to expose? I know I had to remove mine on my Yamaha to get to it. Maybe this could be it. Just thinking out loud..
  12. Creek Runner

    Creek Runner Well-Known Member

    Ding, ding, ding and the winner gets!
  13. cutrunner

    cutrunner Cert. Yamaha technician


    Either take it to a shop or take it apart, leave the idle mixture screws on the outside alone, soak it in good carb cleaner (merc powertune) for a day or two, clean with brakeclean and blow thru every oriface with air, put it back together and go.
    As long as no one messed with the tuning screws it should run darn near perfect, like the factory desired
  14. Dillusion

    Dillusion devilray snob

    The air fuel mixture on these is blocked by a cap.

    No, the outboard is not going to a mechanic.

    No, the carbs were not serviced by a tech. When I got there the guy said he did it himself....awesome I know.
  15. Dillusion

    Dillusion devilray snob

    I just took apart the fuel enrichment housing and pump. One of the metal paddles inside was completely disconnected, the screw and nut came loose. It was also full of black and orange debris.
  16. Creek Runner

    Creek Runner Well-Known Member

    Just going by what you said.

    I don't care if you do it your self or take it to a shop all my motors run fine to each his own. I was just offering you advice on what you should do as you are not a trained marine tech. I mean really it's $175 to have a shop go through them and then there done right and no guessing, BTW if they are not right they will burn a piston up and you will need a rebuild.
  17. el9surf

    el9surf Well-Known Member

    If you cave in Gordon at central florida marine knows that engine very well. Not cheap but they can fix it. They always serviced both of my yami's (f40 and 50 2strk) and did a great job.
    Hopefully you are not reverse engineering someone elses project.
  18. Creek Runner

    Creek Runner Well-Known Member

    Surf he has a simple carb issue that would take any Yamaha tech about an hour to fix, no reverse eng. going on just needs some who knows what they are doing.

    That motor is about as simple as it comes, Suck, Squeeze, bang that's about it.
  19. Dillusion

    Dillusion devilray snob

    I know what I typed previously, that was before I picked it up and asked the previous owner about it.