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  1. #1
    PWCToday Newbie
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    94 XP 657 - tuning it in

    Finally was able to get the ski off the trailer and onto water with the help of the folks on these forums. I'm down to what seems to be the final tuning of the carbs. When I had it out last night from idle up to about 4500 rpms it would sputter. Going past 4500 rpm, there was a lag and then it would surge up to 7500 - 8000 rpms and the sputter would disappear. My thought is that it's fuel deliver on the low side. The carbs are completely rebuilt, the low speed screws are set to 1 1/4 out and the HS screws are closed. Should I pull the carbs yet again to see if something's clogged or should I start elsewhere?

  2. #2
    Resident Guru hafweigthr's Avatar
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    Re: 94 XP 657 - tuning it in

    When you say sputter do you mean like an intermittent miss like a putt-putt- putt every few seconds? Have you trimmed the spark plug wires? Plugs in good shape and using the watercraft version of the BR8ESs. (Cat # 3961 I think)
    Some skis actually have that miss/sputter while others do not and they run fine except for that. Sometimes this symptom is hard to eliminate but some skis can do this until they get fully warmed up.

    7000rpm should be top rpm higher would indicate too lean and rev limiter should be kicking in.
    The thought that leads to no action is not thought - It is dreaming!!
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    Some people have hobbies - some people have addictions - I have jet skis!!

  3. #3
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    Re: 94 XP 657 - tuning it in

    Correct. An intermittent miss is a better description. It's like brrrr rrrrr rr rrrrrrrrr rrr rrrrrrrrrr rrrr. I just trimmed the wires and haven't tested that yet. I had no idea there were two different versions of the BR8ES plugs. I've got the 5422 vs. the 3961's. I'll have to pick up some of the 3961's. Below are pictures of the plugs, the exhaust leak, and this black "stuff that has made it's way out of the exhaust. The plugs are wet and black. You can see what looks like oil in the exhaust leak and the stuff that dripped onto the ground is like a black sludge.

    PTO side
    CIMG3492.JPG
    MAG side
    CIMG3493.JPG
    Exhaust leak
    CIMG3490.JPG
    Black sludge
    CIMG3494.JPG

  4. #4
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    Re: 94 XP 657 - tuning it in

    Quote Originally Posted by hafweigthr View Post
    When you say sputter do you mean like an intermittent miss like a putt-putt- putt every few seconds? Have you trimmed the spark plug wires? Plugs in good shape and using the watercraft version of the BR8ESs. (Cat # 3961 I think)
    Some skis actually have that miss/sputter while others do not and they run fine except for that. Sometimes this symptom is hard to eliminate but some skis can do this until they get fully warmed up.

    7000rpm should be top rpm higher would indicate too lean and rev limiter should be kicking in.
    I was able to take it out for a very quick ride on the water before the rain came today and it's still doing the intermittent miss thing. The wires have been clipped. It's got new cat #3961 plugs, and I opened up the low side screws just to be safe. It didn't rev over 7000 but would still surge when I went to open it up. Any thoughts on what to check next?

  5. #5
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 94 XP 657 - tuning it in

    Get that exhaust fixed,leaking,no washers on bolts & I bet there is a lot more issues going on.....

  6. #6
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    Re: 94 XP 657 - tuning it in

    Quote Originally Posted by Grumpy Old Guy View Post
    Get that exhaust fixed,leaking,no washers on bolts & I bet there is a lot more issues going on.....
    Got the exhaust leak fixed. Had to re-tap the holes due to corrosion. Proper hardware is also installed now. Could this an issue with the rectifier? I haven't checked voltage while running but plan on doing that this afternoon.

  7. #7
    Resident Guru hafweigthr's Avatar
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    Re: 94 XP 657 - tuning it in

    That sludge is not good. The reason your ski sounds like it does is the plugs are getting shorted out by the excess oil/gas/moisture that exists in your engine.
    History of the ski would be a start for eliminating areas that could be causing your problems. Once your engine is not running correctly it will create all the carbon(sludge -incompletely burnt oil and gas) that you are seeing. Biggest cause for this would be low compression . But seeing that both plugs are completely wet I am not sure. Do you know what your compression is?
    A bad exhaust leak will cause significant combustion problems since the air source for your motor is the inside of the hull and you are filling your hull with oxygen deprived air from the exhaust.
    657 ignitions do not suffer from rectifier/regulator problems like the 787 due to different type of ignition.
    The thought that leads to no action is not thought - It is dreaming!!
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    Some people have hobbies - some people have addictions - I have jet skis!!

  8. #8
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    Re: 94 XP 657 - tuning it in

    So the ski was a mess when I bought it. The engine had ingested water and seized up. It was to the point the water jackets cracked at the top of the jugs and the crank was frozen up as well. I had a complete rebuild done. New jugs/crank the full 9 went into it. The carbs were pretty ugly as well but I bought the rebuild kits, including N/S, took my time and got those back to looking cherry. The popoff on both sides is just a hair under 20psi and they hold pressure well. The line between the carbs was the last TEMPO line that was remaining but I replaced that during the carb rebuilds with the USCG A1 line. Last compression check was 155/155 but I can check that again today.

    That's good info. about the rectifier/regulator. I wasn't sure if the problem carried over to the 657.

    It's driving me nuts because once it surges and gets towards the top end it really hums.

  9. #9
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    Re: 94 XP 657 - tuning it in

    Checked the compression and it's the same. Also took some pictures of the plugs and they're below. This was after about a 5 - 10 minute ride and they're brand new. I noticed the MAG side has less oil around the rim.

    MAG side
    CIMG3499.JPG
    PTO side
    CIMG3495.JPG

  10. #10
    Resident Guru hafweigthr's Avatar
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    Re: 94 XP 657 - tuning it in

    The exhaust leak into the hull could have been the start of your problems(after rebuild) and that gunked up your new motor and exhaust. Still looks like your plugs are too wet. I would probably just run your ski and once you run good the build up should clear and then most of the issues may clear up. Are you running extra 50:1 oil in your gas for the first tank on your rebuild?
    Who did the rebuild? Are they reputable?
    Last edited by hafweigthr; 10-13-2017 at 04:27 PM.
    The thought that leads to no action is not thought - It is dreaming!!
    Think Big!!

    Some people have hobbies - some people have addictions - I have jet skis!!

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