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  1. #1

    Yamaha SUV is Bogging under load. Runs fine on hose what could be the problem?

    Aloha everyone,
    Happy New Year!! Well after sitting for a good year or more I got a new Battery & sprayed starter fluid in the carbs & Started my Yamaha SUV ski. It started right up so we put her in the water, she ran well for about 15 min, then seemed to get super bogged.. wouldn't go higher than a bit above idle. if I gassed it it would bog & want to die... We pulled it out of the water & went through her for the next day.. we siphoned off the gas put some fresh gas in it. One of the big hoses in the back battery compartment had come off & some water was in the hull we replaced the hose clamps & thought that may have been it. Continued to do due diligence on checking for loos stuff, Felt we had it checked out. We ran it on the hose for 30 min it ran fine & even revved up just fine sounded good! we put it back in the water & same thing. No power under load. as soon as it was in the water with load on the motor it bog's. I spoke with my mechanic & he is thinking carbs are in need of a rebuild. Could this be the case? Just curious how & why it would run fine on the hose & not under load if it is the carbs... It sat for over a year with non ethanol pre mixed gas in it. I did not turn off the fuel & burn out the fuel from the carbs so they did sit there with fuel in them. (no one told me to do that until after it sat!!!) Any way your thoughts?


  2. #2
    wotxxxsd's Avatar
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    Cool

    Carbs are for sure going to need completely rebuilt.
    What's your compression #s?
    Did you fog the engine before it you stored it?
    New fuel lines also.
    Fuel filters too..

  3. #3
    RaiderMagic's Avatar
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    bought my XLT land locked, no water ride. ran fine on a hose....1st ride out I almost got stranded. Carbs needed a complete rebuild. we have the same motor.

  4. #4
    What I would do befor I tear into anything is check the compression on all 3 cylinders......if it throttles fine on the hose and bogs down in the water its more likely the carbs or a compression problem.....Replace all the fuel hoses while you have the carbs off....get a oil gun also and grease the bearings on the driveshaft as well

  5. #5
    Echo's Avatar
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    All above is solid input. Check compression first, u might of toasted a cylinder in the 15 mins of good running with clogged carbs and bad fuel. If compression is good rebuild carbs. DO NOT after market carb kits, get Oem kits, no exceptions.

    For future reference fuel is bad if left sitting for just a couple months without treatment. Two strokes need good fresh fuel period. Carbs should be rebuilt no mater what the storage procedure for such a long duration as a year. That is just my opinion, but cheaper than risking a motor.

  6. #6
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by [email protected] View Post
    Just curious how & why it would run fine on the hose & not under load if it is the carbs.
    no mystery there. thats just how they are. the fuel demands of an engine with no load are completely different from the fuel demands of a loaded engine. And these engines are heavily loaded when in the water when compared to on land.

  7. #7
    Aloha & Thank you to those of you that responded!

    Update. I went & did a compression check on the engine. Cylinder 1. 120 psi. Cylinder 2. 30 psi. Cylinder 3. 120 psi.
    looks like I have lost compression on the middle Cylinder!

    Ok So I have a few questions for you guys that replied,

    How would old fuel cause a loss of compression in a cylinder? I had one poster saying that he thought running old fuel throught the carbs if clogged could have ran lean & hurt the top end of my cylinder.. How is this possible? The Fuel is Premixed so how can it be running lean or rich? I thought that was in the mix? I am totally open to your comments.
    I will be pulling the heads off to see what happened in the middle cylinder. sense I am going to go in this deep I will replace the fuel lines, Fuel Filter, & clean the tank, I will also have the carb's rebuilt, but again would like to ask why this step is necessary as I don't understand how the carb's would have caused the loss of compression.

    Is rebuilding the carbs something I should attempt or not?

    Now that I am going to pull off the head is there anything you guys can tell me to do don't do while doing this? Tips? Is there a how to thread on this?

    I helped a buddy do this same thing a year ago & I have the book in front of me. Is there a way to take off the head without taking it completely apart (ie exploded diagram) looks like there are two parts to the head.. Top end & middle.. can you loosen the long bolts & pull the head off in one chunk? if so which ones do I take out?

    Any help, Tips, Or suggestions welcome!
    Mahalo,


    Erik

  8. #8
    Echo's Avatar
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    Carbs/fuel are the weak point of two strokes, and result in 90% of engine loss. These two things need to be 100% or you will have issues. There are orings(will dry out and crack) springs(can get gunked up) diaphragms(can dry out shrink crease) screens that clog/corrode due to bad gas, and water from condisation. Gas evaporates oil does not it stays behind and sticks to things, also 2 stroke oil dont stay good for ever, once the seal on the bottle is broke it starts breaking down. Today's 2stroke oils have many additives and detergents. Gas itself goes bad in many ways in just months, I even write dates on my cans every time I premix after a couple months old premix goes in my jeep, not even good for my hand held lawn equipment IMO.

    Head/head cover will come off in one piece. You will find a scratched up cylinder and piston, will require machine work and a new piston/rings(some will say all three holes need to bored the same, I am one of those people, some just have the bad one bored tho). Head will prob be beat up a little also, most likely usable with some cleaning up.

    All this is a result of bad carbs/gas due to sitting for a extended period of time. Also if it was not winterized/stored properly, rings coulda been stuck, this is unlikely tho as it ran good for 15 mins when first started.

  9. #9
    Yamaha artisan Cutlass's Avatar
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    Erik, you've got a lot of reading to do.
    Lean refers to air to fuel ratio, not fuel to oil ratio. Bad gas or clogged carbs result in a lean A/F ratio. Air/vacuum leaks into the engine also result in lean A/F ratios. 2 stroke engines (especially high performance 2 strokes) are very sensitive to Lean A/F ratios.
    Think of it this way...water from the lake/river/ocean keeps the cylinders cool and gas keeps the piston cool. Lean A/F ratios burn hot. Rich A/F ratios burn cooler. The heat from a lean A/F ratio is transferred into piston. Hot pistons expand so much that they start rubbing on the cylinder bore. That'll ruin the pistons and rings fast.
    The hot lean burn can also melt pistons.
    Its critical to have and engine that is 100% sealed from air leaks and with carbs setup to run rich.

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  11. #10
    I know I have a lot to learn!!!

    Thanks for the info! There were a couple hoses in the back where the Battery were that hah corroded & broke off. I beleive this was in the cooling box area... there was a bit of water in the hull not much. & a hose that seemed to do with air that was off.. this could have been it. How do I know if I need the carbs rebuilt or not. any tests I could do to see if there working well?
    thanks!!
    Ill post photos of the results of the tear down!
    mahalo,
    Erik

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