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  1. #1
    PWCToday Regular goingpwc's Avatar
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    GTX 97 bogs during transition from idle to mid-throttle

    I thought I would try to get some expert advise from you forum members. You have been very helpful in the past.

    I have a 97 GTX with 142 hrs. I have been experiencing difficulty transitioning from idle to mid-throttle. The ski just bogs badly. You have to modulate the throttle to get it through the transition. Once you get through the transition it runs great. I checked the cylinder compression (145 psi at 4200 ft). I rebuilt the carbs and keep everything stock. The pop-off pressure is 27 psi which is within specs for this engine. I checked the fuel pump to see if it would hold 4psi for 30 sec. It didn't so I replaced the pump medal cover because it was leaking and would not seal even with two gaskets. The new cover resolved the issue. I installed a fuel primer system which helped the starting issue so I do not have to crank the engine for an extended period to get it started. I now hit the plunger three times and the engine immediately fires. I did not have a new set of plugs to check for lean or rich carb issue between idle and mid-throttle. However, I adjusted the low speed needles from 1 turn out to two turns out 1/4 turn at a time and the issue did not improve at any of the settings.
    I am out of ideas as to what I need to do to. I would appreciate any help you could give me. I hope I have given you enough info to help sort it out.
    Thanks for you help !!!

  2. #2
    PWCToday Regular goingpwc's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    Anyone have any thoughts on how to over come this problem
    Thanks

  3. #3
    PWCToday.com Is My Home Away From Home kcr357's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    Try new plugs, and check the needle and seat seal by holding the needle closed and putting some compressef air to it.
    Use wd40 or oil and look for bubbles
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  4. #4
    PWCToday Regular goingpwc's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    kcr357,
    Thanks for your response. I have tested the seat O ring and needle and seat many times and they are holding pressure and not leaking. I am following Mikuni's test procedures. I don't believe changing plugs will help this issue since the engine performs very will after getting through the transition from idle to 1/4 throttle.
    Based on what I have read both in the Mikuni service manual and on various pwc websites, the transition adjustments need to be held in a very tight tolerance for the transition to be successful. The GTX used to transition fine until late last year and all this year.
    Thanks for your thoughts.

  5. #5
    PWCToday.com Is My Home Away From Home bills86e's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    There was a TSB on '97 787's, raves sticking. The cure is use Slotted Raves.

  6. #6
    PWCToday Regular goingpwc's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    bills86e
    Thanks for the response. I have Slotted Raves. My issue is not with mid to high speed, it is transition from idle to mid-speed. RAVES do not open until I believe around 4500 to 5000 RPMs.
    By the way, I did clean the valves recently. They were pretty clean.

  7. #7
    PWCToday.com Is My Home Away From Home freekstyle's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    Did it bog before the primer was installed? Is the 27 psi pop off for stock?
    Last edited by freekstyle; 08-24-2017 at 11:13 PM.

  8. #8
    PWCToday Regular goingpwc's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    freestyle,
    Thanks for you response. Yes the engine did bog before the primer system was install. As I recall it wasn't as bad as it is now, but it did bog. The primer accesses fuel from the return fuel line. I removed the choke plates and installed the primer injectors in the shaft opening. 27 psi pop off is for stock. The entire engine is stock.

  9. #9
    PWCToday Regular goingpwc's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    An update,
    I pulled the carbs and went through them as thoroughly as possible, blowing all the fuel passages out and checking the diaphragms and gaskets. I also pressurize the fuel system and it held pressure although it wasn't 5 psi as specified but 4 psi. It could have been the gauge that was reading low. I thought 4 psi was close enough. Unsure of what pop-off springs were in the carbs I replaced them with 80 gram springs. That changed the pop-off pressure from 27 to 35 psi which is still within specs for this engine. I purchased new br8es NGK plugs. I took the pwc to the water and experienced the same problem. I checked the plugs for color and wetness. The PTO plug seemed a little damp. The Mag plug seemed to be dry. The color on the ceramic center electrode was pretty clean with no color change on both plugs. Then I ran the pwc between 3/4 and full throttle for 15 to 20 mins and looked at the plugs. They were a light tan color.
    While trying to get the engine to transition I hit the primer and I was able to get the engine to rev up and get through the transition. This leads me to believe I am starving the engine during the transition and that is why it is bogging. If that is true, what do I need to due to resolve the issue????
    It was suggested that I check battery voltage with the engine not running and running. I did that: not running the voltage was 12.7. Running was 13.54. I believe that is acceptable.
    I am totally stumped. I believe I have a fuel starvation issue but do not know how to resolve it.
    One other note, the spec for the jet at sea level is 140. I am at 4,000+ above sea level and both carbs have been jetted with 132.5., which I think is OK. It has always been 132.5 even when the pwc was performing well in the past.

  10. #10
    Resident Guru hafweigthr's Avatar
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    Re: GTX 97 bogs during transition from idle to mid-throttle

    If the carbs and the fuel system are rebuilt properly you should not have a bog. However if you removed the choke plates you will have to enrich the fuel mixture some since now you have changed the air flow through the carbs. On a 97 GTX (if stock) you should be able to rebuild the carbs with stock parts and set the Lows to 1 3/8 out and the high PTO carb to 1/2 and get great results (pop off should be about 35). Did you verify that both carbs return orifices were open--- this is often missed during carb rebuilds.
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