1997 GTS 720 backfiring - Page 2
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  1. #11
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    Re: 1997 GTS 720 backfiring

    Don't have a RAVE valve? did you mean rotary valve, and yes it was set at 147 and 65.5 per manual. I gap the plugs at 0.21. I did try the plugs at 0.25 and down to 0.18 to see if that made any improvements, it had no effect.

  2. #12
    PWCToday.com Is My Home Away From Home kcr357's Avatar
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    Re: 1997 GTS 720 backfiring

    Crazy suggestion-post everything youve done so far so people arent wasting their time telling you to check stuff thats already been covered.
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  3. #13
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    Re: 1997 GTS 720 backfiring

    Why does the engine backfire,is the engine too lean for some reason????

  4. #14
    PWCToday.com Is My Home Away From Home Cliff's Avatar
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    Re: 1997 GTS 720 backfiring

    Quote Originally Posted by homebrewdoo View Post
    Don't have a RAVE valve? did you mean rotary valve, and yes it was set at 147 and 65.5 per manual. I gap the plugs at 0.21. I did try the plugs at 0.25 and down to 0.18 to see if that made any improvements, it had no effect.
    I did mean to say Rotary Valve(RV). Not RAVE Valve. 720 motors do not have R.A.V.E. valves.

    Is the ski backfiring through the carbs or the exhaust?

    Also, if you feel the ski is running lean. You can turn the Low Speed Adjustment screw counterclockwise to richen the mixture up. But having the ski in the water and the pump under load is the best way to tune the carb. Running the ski on the hose puts zero load on the motor and is not an accurate method for tuning.
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  5. #15
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    Re: 1997 GTS 720 backfiring

    backfiring thru the carbs only over 1/3 throttle, i am going to pull the carb apart and double check all passages, install all new parts

  6. #16
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    Re: 1997 GTS 720 backfiring

    Are the 3 low speed bypass holes the same size?

  7. #17
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 1997 GTS 720 backfiring

    I feel like you may have a stator issue. The only way to know for sure would be to take a dmm to the water with you for checking ac voltages while running. Why don't you run it on the trailer strapped down, hold it throttled up while it's crapping out for 20 seconds then pull the lanyard......like a throttle chop. Then pull the spark plugs and show us a pic.
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  8. #18
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    Re: 1997 GTS 720 backfiring

    Remove carb and disass'y. remove jets, 2nd time, to clean with carburetor cleaner, blow out holes with cleaner, used wire to insure all 3 holes were clear. note All 3 bypass holes are different sizes, one is .022 and the other two a smaller, I checked 5 or so other carbs in my shop and found that only one hole is .022 and the other hole is smaller. Rebuild using OSD kit with new valve seat/needle, checked pop-off 3 times at 35 PSI. installed on motor and test run on hose, ran better but still had some problem above 1/2 throttle (backfiring). Removed carb and installed 70 low speed jet, old one was 67.5. ran motor on hose, ran good up to 3/4 throttle. no backfiring. Took ski to river and ran it for 5 min on old plugs, installed new plugs set at .022, ran at 20 to 30% on trailer, removed new plug and took photo of tips, color looks good. Ran at WOT for a speed run, top speed was 45 mph on gps, No hesitation. need to adj low speed idle, will get a tack to set at correct rpm. Photo of plugs after running shows one black and one clean? Q. motor had set for over a year could oil inside motor be the cause of one plug to be black?

  9. #19
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    Re: 1997 GTS 720 backfiring


  10. #20
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    Re: 1997 GTS 720 backfiring


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