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  1. #1

    99xl 1200 top end power loss????????

    So I'm in the final stages of building an entire jet ski. Empty hull to where I am now I have rebuilt or replaced most of this thing, rebuilt motor, carbs, new complete impeller to include the shaft and every thing behind it, fuel filter some hoses I did reuse the fuel lines because they were closed off at time of purchase now this whole project has taken about a month but my problem now

    AT wide open throttle it will cap at about 47 mph on the odometer this is around 7000 rpm, it will drop to 4000 rpm for around 4 sec then climb back up for around 10 sec if u pump the throttle it will not surge any questions or thoughts please help thank you


  2. #2
    urugol's Avatar
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    Did you leak test the engine? A bad seal will do this, if you are getting 7,000 rpm at 47mph doesn't sound like all the power is being transferred as it should.

  3. #3
    no i havent done a leak test ...yet the final screws went in last night and i tested it today and when it was an epic failure i came here when conducting a leak test in your experiance where/ what should i be looking for, the motor that is in there is no more than 2 weeks old and has less than 45min on the clock, any ideas

    ---------- Post added at 08:39 PM ---------- Previous post was at 08:36 PM ----------

    on another note the power valves are cycling, the carbs had factory mikuni rebuild kits, and the only thing not stock is the dplate.

  4. #4
    urugol's Avatar
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    Quote Originally Posted by dirtyd99xl12 View Post
    no i havent done a leak test ...yet the final screws went in last night and i tested it today and when it was an epic failure i came here when conducting a leak test in your experiance where/ what should i be looking for, the motor that is in there is no more than 2 weeks old and has less than 45min on the clock, any ideas
    For starters you are meant to "break in" your rebuilt engine. There is a procedure that allows the rings to seat, if you do not follow it you can do a lot of harm unnecessarily - particularly by pinning the throttle during the first fuel tank. If you pulled the cylinders and replaced rings you must leak test the engine to ensure no pressure escapes resulting in poor performance. I would speak to your engine builder about this, if you did it yourself use the search function there are a few threads on how to do it on the site.

  5. #5
    Well after a compression test I didn't see much point in any futher testing, again I'm curious about this leak test where pressure escapes my engine where / what am I looking for and in your experience what has been a more prevalent failure over all others?

    In other news I down loaded the mikuni bn44 service manual in the diagnostic tree it listed similar operations and recommend high speed adjustment... Will report findings and results of leak test Carb adjustment

  6. #6
    Ok so I talked to a guy in Atlanta who told me cavitation is the word and to correct that with a riva pump seal kit ordered today will install and report in the mean time if any of you have experienced this kinda thing please chime in and let menknow what you found thanks and happy wake.

  7. #7

  8. #8
    alrighty ladies and gentlemen i am pleaseed to report that after weeks of rebuild and wrench turning fun the 99 xl1200 recovery project is a sucess, all leaks, pluged bolts tightened cavitation cured and wide open throttle is everything i hoped it would be, now as for coming on here and getting the guidance and wisdom i was looking for.... not so much but hey what can you really exspect for free but heres what i did pay for, a 1999 yamaha xl 1200 with a newly rebuilt motor, plugs wires, newly rebuilt carbs new intake system reed valves wave eater clips, on the pv's and my favorite part an entirley new pump, housing, filter, impeller and shaft, riva pump seal kit and d-plate, total price $2011.83 than you so very much i was impressed too up untill this point i had trouble finishing lunch yet alone a rebuild of this type.

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