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Yamaha 90 2 stroke fuel problem

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  • Yamaha 90 2 stroke fuel problem

    I'm having a problem recently!! my boat is hard to get on the plain as in running rich throttle slow & it picks up get on the plain & goes along nice!! it's slowly been getting harder to run right!! things I did cleaned all tanks new lines & bulb cleaned motor filter, fitted a fuel filter/ separater cleaned out fuel bowls & pumped the bulb to try & get any junk out re-syned carbs have manual new plugs since having this problem. Things I noticed as when trying to tune the adjusted mixture screws top 2 around 1/ 1/2 out seemed to be good the bottom one adjust in or out nothing no change like carby no working at all!! now when trying to rev motor up it kinda misfires clears itself & revs out as in on the water, another thing that find is after a while the fuel bulb has lost it's pressure!! I tried pumping it up when running & doesn't change anything. Now with the good people here give me some idea's I'm thinking maybe a good clean out of carbys is it that hard to take off & clean each one or better off leaving it up to the pro's which have offered to do at $100 each!! or I've read here about the fuel pump may have a problem & flooding the lower carb 1st & need to buy a new fuel pump maybe the fuel pump looks easier to work on like take old one off bolt on new one, I handy with motors as I race motor cycles & rebuild & repair race etc here in Australia any idea's guys & I know it's cheaper to buy there in the states compared to Australia so will it be worth while buying the parts from there & get them sent here
    Steve


  • #2
    Re: Yamaha 90 2 stroke fuel problem

    As always I like to check compression and test spark on the motors to start out with just to make sure all of that is good 1st, and then you can check fuel pump for a tear/hole in diaphragm.
    you can buy just the parts needed or the whole pump , just remember to get a new mounting gasket as it does not come with the pump.

    If all of that is good then pull and clean the carbs, they are not hard to do ,just make sure you do not mix up parts from one to another as some of the jets are different sizes on the different carbs.
    make sure they go back where they came off of, and you will need a service manual to make sure all adjustments and specs are done correctly

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    • #3
      Re: Yamaha 90 2 stroke fuel problem

      Originally posted by Racingsteve View Post
      I'm having a problem recently!! my boat is hard to get on the plain as in running rich throttle slow & it picks up get on the plain & goes along nice!! it's slowly been getting harder to run right!! things I did cleaned all tanks new lines & bulb cleaned motor filter, fitted a fuel filter/ separater cleaned out fuel bowls & pumped the bulb to try & get any junk out re-syned carbs have manual new plugs since having this problem. Things I noticed as when trying to tune the adjusted mixture screws top 2 around 1/ 1/2 out seemed to be good the bottom one adjust in or out nothing no change like carby no working at all!! now when trying to rev motor up it kinda misfires clears itself & revs out as in on the water, another thing that find is after a while the fuel bulb has lost it's pressure!! I tried pumping it up when running & doesn't change anything. Now with the good people here give me some idea's I'm thinking maybe a good clean out of carbys is it that hard to take off & clean each one or better off leaving it up to the pro's which have offered to do at $100 each!! or I've read here about the fuel pump may have a problem & flooding the lower carb 1st & need to buy a new fuel pump maybe the fuel pump looks easier to work on like take old one off bolt on new one, I handy with motors as I race motor cycles & rebuild & repair race etc here in Australia any idea's guys & I know it's cheaper to buy there in the states compared to Australia so will it be worth while buying the parts from there & get them sent here
      Steve
      I doubt you have a pump problem because all carbs would be affected. Most likley is a dirty carb. If the carb is overfilling then it is a float/needle and seat issue. I just did all 3 carbs on a 90 hp. Removed, cleaned, inspected and re-installed in less than 1 hour. The shops charge about 1 hour labor per carb. About $100.

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