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  1. #1

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    Group K, Kawasaki STXR problem! who is great with troubleshooting!?!

    I bought another used, sitting, STXR and just ran the ski as is for a summer, it started acting up towards the end of the summer and I decided to just freshen the thing up overall rather than chase problem after problem trying to find it. The ski had the same issue as it does now, even after all the work I did so the problem is most likely outside the work performed.

    I tore the engine out, sent the carbs, cyls, and heads out to Harry at Group K for a Stage 2 kit. While Harry was doing the machine work and carbs I rebuilt the jet pump with genuine Kawi parts. I also removed the fuel and oil tanks flushed and cleaned them and reinstalled it with all new Tygon fuel lines. The fuel system is/was spotless.

    I installed Group K's Stage two kit and used all genuine Kawi gaskets per Group K's installation instructions.

    (I am familiar with the STXR and this was the second motor I've done, the first motor I did a complete overhaul top to bottom and rebuilt the carbs as well so I am familiar with the ski)

    I began to break in the ski per Group K's instructions. The ski ran like a top and showed real promise, you could tell, even at partial throttle, the ski was going to be a hot little runner. (my other ski is only Group K stage 1)

    Once the first hour was up I got a bit more liberal with the throttle and the ski didn't seem to be running so hot.



    In the idle to 4000 rpm range the ski is fine under slow throttle application, quick throttle application will cause a bog that will not clear up unless the throttle is released and re-applied more slowly. the sluggishness clears up at 4k. At 4-5k the response seems snappy.


    At 4000-5000 rpm the ski responds well to throttle but once over the 5000 rpm mark the ski begins to bog down again. The ski is peppy at a steady 5k, but a quick jab of the throttle and the ski will seem to be smothered. If throttle is applied quickly once the ski is humming along fine at 5k, it will hold at 5k momentarily then slowly stumble and the rpm's roll back towards idle.


    Once again the top end is all fresh, Group K overhauled the carbs, fuel lines are new, the fuel tank was removed and cleaned prior to engine install, all new fuel lines......not that it matters because the ski did this same exact thing before the top end and carb work!!! I figured the carbs had an issue or dirty fuel system or something and figured it would clear up after I did all the work....well it didn't!

    First thing I did was swap out the complete ignition box assemblies with my other ski....plug, wires, and all. I ran the ski and the problem remained unchanged. I put the ski away for the winter planning on having to take the carbs back off for a fuel issue.

    I assume it is fuel related but it is hard to tell if it is a lean condition or a rich condition? It seems rich the way it bogs and stumbles.

    I recall a friend having a similar issue, his fuel pump
    diaphragm went bad and fuel would flood the ski ....I began to think this could be the issue. Or that the fuel pump is bad and it's not being smothered but rather starved of fuel.

    Spark plug readings are not much help as I have the oil injection on top of the 50:1 premix running as required for break-in. (The ski has 1 hour of under 5k time on the motor)

    Any ideas? I could just swap a fuel pump as it is the only item that has not been changed between the original ski and after the Stage 2 upgrade work was done.


    TPS sensor or something???

    I am waiting to hear back from Harry at Group K and I am sure he will be most helpful as he always is but i figured in the meantime someone may have some insight.

    ...and to reiterate this is not a Group K issue as I had an issue prior. I would recommend Group K to anyone! This is the fourth engine they have done for me! You won't get better service elsewhere!


    Any help would be appreciated!!!


  2. #2
    steve45's Avatar
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    Fuel system venting? Air leak on the selector valve? Are you running a primer? Have you tried giving it a little choke to see if it helps?

  3. #3
    Let me out of here......I need to go on Greenhulk!
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    The fuel pumps arent cheap but you just spent all that money on a new motor I would say easily worth the $150 for peace of mind knowing you have good fuel pressure. Maybe you could tee in a pressure gauge and check your fuel pressure.
    Like was said above you could bypass the selector valve to rule that out.

  4. #4
    88kawi5fiddy's Avatar
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    Quote Originally Posted by TMiller View Post
    The fuel pumps arent cheap but you just spent all that money on a new motor I would say easily worth the $150 for peace of mind knowing you have good fuel pressure. Maybe you could tee in a pressure gauge and check your fuel pressure.
    Like was said above you could bypass the selector valve to rule that out.
    .
    Or run a mikuni fuel pump and tap into the kehin fuel rail and return. Would cost 60 plus two fittings.

    Question for you, how do the carb needles look? If you can even SEE a line in the black viton tip, all sorts of weird things can begin to happen.

  5. #5

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    I believe I did try the choke at the end of last season and it did not seem to make a difference.

    I thought of the fuel venting as well but don't think that the issue would be so consistent to an exact rpm range. Like I said the ski will buzz along at 4500rpm all day so it is not a low pressure issue in the fuel tank. The vent line is new and clear and since that had been addressed since the ski first had an issue I would assume it is not an issue now.


    If a Mikinu pump is 60 bucks I think I'd rather just replace the stock pump with new for the same amount of work and 60 bucks more. I recall my friend having an issue with his pump on a Yamaha ski and his ski passed fuel through the compromised pump diaphragm and flooded the engine while at rest. I feel adding an additional pump is a waste of time and money prior to ensuring the stock pump is serviceable.

    Now an air leak at the selector valve could be an issue, but once again I would be highly skeptical as to the issue being very very consistent to a rpm range...but possible I guess. I can bypass the selector and run a separate line direct tank-to-pump and try that but with clear Tygon lines though I should be able to just look and see if air is introduced while the ski is running. Once again I assume at some point the ski would rev over 5k even for a second and be a bit more inconsistent with such a problem.

    As far as the carb needles look I do not know, the carbs are installed at this time, but they were brand new and installed as assembled by Group K. Group K rebuilt them and did their proprietary Stage 2 modifications to the carbs ...whatever that may be.

    I would have preferred to do the carbs myself but Group K seems to keep the mod proprietary and wanted to do it themselves. So the carbs were assumed to be good at first and since the issue is consistent with the problem prior to the carb overhaul I was confident that something else is the issue. Of course this may not be the case.

    The only thing I could think of was the fuel pump, as that was not changed in this before and after scenario.

    Or maybe that Group K had made a mistake and the carbs were incorrectly jetted?

    I will call Harry today and follow up.

  6. #6
    Let me out of here......I need to go on Greenhulk!
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    Quote Originally Posted by 88kawi5fiddy View Post
    .
    Or run a mikuni fuel pump and tap into the kehin fuel rail and return. Would cost 60 plus two fittings.

    Question for you, how do the carb needles look? If you can even SEE a line in the black viton tip, all sorts of weird things can begin to happen.
    I would think Groupk wouldve checked popoff on those when he was in there but maybe not. Ask when you call.

    I always remember guys running dual mikuni pumps on these motors. I dont know how the output of the stocker compares to a single mikuni, anyway something to consider.

  7. #7
    88kawi5fiddy's Avatar
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    Quote Originally Posted by TMiller View Post
    I would think Groupk wouldve checked popoff on those when he was in there but maybe not. Ask when you call.

    I always remember guys running dual mikuni pumps on these motors. I dont know how the output of the stocker compares to a single mikuni, anyway something to consider.
    I would too, but you never know, unless you know. My last set of ultra carb needles were so worn the Vito tip was actually stuck inside the seat. Dunno how it was even running. An electric fuel pump is also an option, just because. Doesn't hot products have an aftermarket ultra fuel pump rebuild kit?

  8. #8

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    I talked to Harry at Group K , those guys are always a pleasure to deal with, Harry believes that the fuel system is not sealed and the required pressure is not being held in the tank. He stated that that is typically the symptom. I hope, as that would be an easy fix.

    I purchased a new tank vent check valve last night just in case that is the issue.

  9. #9

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    Check for cracks in the plastic fuel filler neck and the gas cap. The gas cap cracks with age and the filler neck cracks when the cap is over-tightened. Also, inspect the rubber gasket on the underside of the gas cap, as well.

  10. #10

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    Quote Originally Posted by GlenT View Post
    Check for cracks in the plastic fuel filler neck and the gas cap. The gas cap cracks with age and the filler neck cracks when the cap is over-tightened. Also, inspect the rubber gasket on the underside of the gas cap, as well.

    Great, thanks for the info!

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