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  1. #21
    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: Pro mechanics only, need opinions

    Quote Originally Posted by Myself View Post
    What do you see John? Engine was not assembled by me. I thought the fuel wash looked great for a Kawi triple. I've never seen a lean condition grab rings at the exhaust port. Also did you see the scuffing on the intake side of that one piston in the exact shape of the boost port?
    Just like Chris said. #1 Cylinder is melted on the exhaust side from heat, from being lean. Rings expand into port, snag, and make carnage.

    Now I also wonder where the pistons in backwards? #3 ring obviously snagged a port as well, and I wonder if they were in wrong? Maybe the ports weren't properly chamfered, and the rings caught a corner? Mybe just to tight of tolerances? How many hours on engine since rebuild? Why do the pistons look like someone sanded them with sand paper side to side?

    Piston wash is still a little leaner than I like.
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  2. #22
    PWCToday.com Is My Home Away From Home hyosung's Avatar
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    Re: Pro mechanics only, need opinions

    hmmmmm,
    im not a pro mechanic, so i cant comment and say what really caused the top end melt down... however i can leave it to the exspurts to guess!!!
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  3. #23
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Pro mechanics only, need opinions

    My comment was just in general with reference to detonation and catching a ring. As far as your specific failure: It appears that you may have a couple different things going on, not the least of which is a lubrication issue. And no I do not see a cylinder ridge. In fact, I don't even see a pic of the cylinder?

    Regardless, that kind of excessive wear would indicate a lubrication issue again. However, the ring catching on #1 and #3 and the piston crown damage on #1 is not what I would expect to see with an oiling issue alone. Just based upon the three low res pics, I would guess that there was an air leak and/or water ingestion on #1 from a blown head gasket and some type of oiling or a water ingestion issue through the carbs on all three cylinders??

    I also think it is odd that you have two cylinders catching a ring on the exhaust side. Having seen everything up close what is your thinking on it?

    Quote Originally Posted by Myself View Post
    Right, except look closely at #3. Exact same ring snagging pattern with no sign of a lean burn or deto or excessive heat. Also the inside of the pistons show no sign of excessive heat. And what do you guys think of the cylinder ridge? How many years does it take to ridge one like this? Ive seen it on 175 hour 951's and 150,000 mile small block chevys.



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  4. #24
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Pro mechanics only, need opinions

    Please excuse hyodung... A breakfast burrito backfired at his moment of his conception

    Quote Originally Posted by hyosung View Post
    hmmmmm,
    im not a pro mechanic, so i cant comment and say what really caused the top end melt down... however i can leave it to the exspurts to guess!!!



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  5. #25
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Pro mechanics only, need opinions

    Ok, cat out of the bag. This is an SBT engine. It was warranted because the first shop failed to clean the fuel system and find creased/deformed fuel pump diaphragms. Machine ended up in my hands and I installed the engine March 2017. Along with rebuilding all 3 carbs and flushing crud from fuel tank. We experienced severe flooding this year, literally washing houses and bridges away along the Norfork river. All campgrounds and launches were underwater. Customer only began to ride the ski end of June, first of July. I personally dialed in the carbs on the water with plug readings and a temp gun, as I do with any carb work. Customer calls weekend before Labor day, ski was great then just bogged out and they limped it back to the launch. No hour gauge on this model but full seasons in my area run 20-30 hours. So, guessing 20 or less. I'm about the only one in between 2 large, very nice lakes that wrenches on skis. Told customer I'm too busy, will need to be winter project. Tore into the engine last weekend and find this mess. My thoughts after seeing the heavy ridge at the top of cylinder 3, and ports snagging rings, along with shadowed wear of the boost port, got me thinking piston rocking. Got out the digital caliper and found about .010 clearance. Now, there are still honing marks visible in the cylinder. AND much of the black coating is still visible on the pistons......except wear intake and exhaust side....again making me think excessive clearance and piston rocking. BUT...with all that excessive clearance how could there possibly be honing marks still visible?? We're talking minimum of .005 wear which DID NOT come off the piston. I strongly believe this cylinder was set up VERY loose and therefore led to premature failure. I also believe, seeing as #1 and #2 piston show the EXACT same ring snagging failure that #1 snagged and wore out the piston allowing for the piston burn through. Instead of it burning from the top down as in a severe lean failure. As for the sideways scuffing on the pistons.......we'll have to ask SBT on that. My whole point for all of this is even though the engine is out of warranty this would not have happened if it had been built properly. Just trying to get other pro opinions so SBT can see them. Would like to get some parts comped or deeply discounted to put this back together for the customer that already spent a small fortune on this machine.
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  6. #26
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Pro mechanics only, need opinions

    imo, it is highly unlikely that .010" piston clearance would cause rings to hang up on the exhaust ports or cause that kind of piston/bore wear.

    .010" clearance would not surprise me with an SBT rebuild, but more often than not I see collapsed piston skirts as the reason behind excessive piston clearances and those pistons look like they have been taking a real beating... I am still guessing that you have more than just piston clearance issues?

    Also, hard to tell from the pics, but the damage to #1 piston does not appear to be from chunks of ring impacting the top of the piston? Or does it?? Is there matching damage to the head also???

    Did you measure piston taper? Should be at least .011".

    What do you say hyodung?



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  7. #27
    Thinks everythng sux =) Top Dog vomitspot's Avatar
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    Re: Pro mechanics only, need opinions

    This is an SBT engine
    there is your problem
    nina hagen daz

  8. #28
    Top Dog orangefinger's Avatar
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    Re: Pro mechanics only, need opinions

    wow ....huh at one point I thought u lost a crank spacer/washer from the rods and it got pushed up .....

    that's so extensive and how on earth will u get this warranted with SBT .......

    Please elaborate a tiny but more , so they missed to clean up ports after bore and hone and rings got snagged ?
    or bore was too loose in one cylinder , not matched to specific piston size ?

    Thx for this great mystery , I am by all means no pro but love to learn more info always ...
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  9. #29
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Pro mechanics only, need opinions

    Quote Originally Posted by mcn6 View Post
    imo, it is highly unlikely that .010" piston clearance would cause rings to hang up on the exhaust ports or cause that kind of piston/bore wear.

    .010" clearance would not surprise me with an SBT rebuild, but more often than not I see collapsed piston skirts as the reason behind excessive piston clearances and those pistons look like they have been taking a real beating... I am still guessing that you have more than just piston clearance issues?


    Also, hard to tell from the pics, but the damage to #1 piston does not appear to be from chunks of ring impacting the top of the piston? Or does it?? Is there matching damage to the head also???

    Did you measure piston taper? Should be at least .011".

    What do you say hyodung?
    Yes #1 damage is all piston ring debris. Yes head matches. I will measure taper and post findings with more pics this evening. #1 and #3 exhaust ports are clearly beaten by rings.
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    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  10. #30
    PWCToday Guru Supaserial's Avatar
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    Re: Pro mechanics only, need opinions

    Are the locator pins still in the pistons?

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