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  1. #1

    Did I smoke my motor? Oh yea, Hi guys new to the forum.

    Hey all, wish I was introducing myself under better circumstances. This is going to be a long one, but I've done a ton of searching and couldn't find any help so Im hoping someone can give me their 2 cents.

    Background - I'm an above average mechanic (I am a licensed aircraft tech on both jets and piston powered aircraft), I've been around small two stroke and 4 stroke engines all of my life. Lots of boating experience of all sizes, including jetskis but not since '98 or 99, and unfortunately I didn't work on those skis very much because I was a bit younger at the time.

    Two days ago I bought two yami GP800R and a XLT800 to mess around with, nice looking skis with 90 hours on them. I did a complete prebuy inspection on them, meaning I ran them both in and out of the water, did a compression test, etc etc etc, pretty much everything recommended on this site and others after doing searches for info. Both skis checked out perfectly, except both had brand new autocraft batterys, and they are junk, and it was apperent that the xlt bat was bad and autozone replaced (I actually upgraded to a sealed battery for the price difference). The battery part will be revisited later in the story. The fuel valves were stuck on as the guy said he never moved them and they eventually froze. Also the GPR had trouble idling until warmed up, but once warm it ran like a clock, I figured I just needed to clean the carbs.

    Took them out today. About an hour run time, but high speeds and big throttle changes only maybe 15 minutes of that hour. Initially they both ran perfectly, then at minute 12 of highspeed jetski type offshore riding, the gpr bogged and quit. Started it up, ran, bogged quit. Did this a few times, battery started to get weaker (rather quickly actually, so I was thinking maybe it was a bad battery like the other one was). I got it running a few times, and it would run a bit for different lengths of time, but eventually would bogg out on the way back to the dock. A few times the starter wouldnt even turn it right after it stopped and I would have to wait for the batt to regain some of its charge (Anybody see where this is going?)

    About 100 yards from the dock mechanic what the heck is goin on mode kicked in and mind started putting everything together and I felt like the engine was making a knocking sound louder than before, and also I was seeing hardly any smoke at all comming out the back, infact I only remember a puff but I shut it off pretty quickly after that.. I shut it off as a precaution after that and got towed in by the other ski. After that, while trying to flush it back at my place and diagnose, it won't idle now without throttle, the starter spins (or seems to spin) slower than before but with a voltmeter the voltage only drops to 11.5 when trying to start (the other batt would drop to 6.6volts, so I new that one was toast the the battery tester at advanced auto proved me right). Also, when I did have it running on the trailer, I noticed pretty much no smoke coming out while it was running on the trailer, versus my xlt that smokes like crazy. (It smoked when we ran it on the trailer during the prebuy inspection, however it was cold then, and I haven't owned this ski long enough to know what it does yet warm vs. cold, they were warm when we were trying to flush them out after all this). I also noticed the xlt has seems to have the same loudness of knock at idle and just above which I think is normal for these 2 strokes? Like I said that one is definitely getting oil. So hopefully I was just Worrying myself over nothing on that one....

    I looked at all the oil lines, every thing is on, I took the oil filter/level sender off and the tank seemed to be filled to the hill. How much oil should it use in that amount of time? How can I tell if this thing is getting oil? Just by looking at the smoke and level in the tank? Is there a more definitive way to know? Did I smoke this motor or is the carb just gummed up and another bad batt? Is the battery draining so quickly really the piston seizing in the cylinder? Allowing me to turn the motor over better once it cooled a bit?

    Its dark now and I can really do anything to it since I have no outside lighting and no garage. Its driving me nuts to have to wait until tomorrow. A buddy is letting me borrow his boroscope (tiny camera/light) so I can look inside the cylinders and check them out. Also will do a comp test if they look ok, and switch the new battery on the xlt with the one thats on the gpr. I've never wished for gummed up carbs more in my life.

    What do you all think? Obviously tomorrow will tell allot. I'm switching the premix after this no matter the outcome cause It will forever haunt me now if I don't. Thanks, Nate

    **PS can a moderator fix my title? Obviously its supposed to say Hi and not I
    Last edited by 800n; 04-24-2013 at 09:55 PM.

  2. #2
    Update: I couldn't help myself, went out pulled both plugs. The bottom of both plugs were bone dry, so was the top of the piston. (versus the xlt, plugs half what i would call moist and half dry, and the top of the pistons looked wet)

    I could turn the intermediary shaft no problem by hand with no unusual grinding or anything.


  3. #3
    wotxxxsd's Avatar
    Join Date
    May 2012
    Even if you run the oil injection system its always good to add a little bit directly to the gas tank just in case the oil injection system takes a dump.
    Do a compression test now see if its different than when you bought it.
    Also its very wise to be premix.
    If compression is the same as when you bought it your Carbs need rebuilt.
    Also check you battery connections and wire brush any rust off your connections.

  4. #4
    I've always been tought to warm the engine up before a compression test to make sure the rings were seated right and get true numbers. I don't want to run it now.... thoughts?

    Also, could a bad battery make the ski not only hard to start, but run bad and do funky things to the ignition system? I should also say that I never got any warning lights/beeps.


  5. #5
    wotxxxsd's Avatar
    Join Date
    May 2012
    You can do it cold.
    I don't warm it 1st..

    Dry plugs mean it was locking up on you.

  6. #6

    Join Date
    Aug 2006
    If the carbs are starving for fuel, you will burn it up no matter how good the oil pump is going. The problem is todays gas really gums up in carbs that sit unused a lot, just like a waverunner. I just had 2 sets apart, one with one year and one with 3 years on the last rebuilt or cleaning, and I was surprised how much crud was in the little internal filters and the adjuster screws. Before you pull it apart, be sure to leak test the engine for air leaks, otherwise you may miss the real problem. Lots of good info one here how to do most anything. Good luck!

  7. #7
    LT1, could you point me to a good leak testing thread? By pull it apart you are meaning for a top end rebuild? I imagine you didn't mean before I do anything any all because I would have to put a block off plate on the intake and exhaust and then pressurize it?

  8. #8
    Little update, checked comps, front cylinder is where it was when I bought it, the rear might be down 5psi. Stuck the boroscope in there and the pistons looked fine, cylinder walls, both, had some light vertical scoring on the left rear sides of both cylinders, seen that before on other good running motors (I realize its not optimal), its also impossible to tell how deep the scratches are with the scope, they may be extremely light. But it definately didn't look like anything melted, went bang or other major destruction went on in there so I'm hoping I'm ok. Went to Riva and scooped up two carb rebuild kits and an oil block off plate so hopefully will be running again very soon.


  9. #9

    Pulled the carbs apart and they are surprisingly clean, however soaking the jets in hops gun gleaner and still need to throw cleaner in there and blow out the carbs with my compressor. just a few tiny specs in each of the little filters though, really though I would see more gunk... New carb kits for the rebuild. Going to bypass my fuel selector knob as well since its stuck, who knows what else that means in there.

    Any and all input is appreciated, atleast so I feel like im not talking to myself while im in the garage.

    I just want to get it back together, wish I didn't have to work for a living its getting in the way.
    Last edited by 800n; 04-25-2013 at 11:34 PM.

  10. #10
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    You description sure sounds like a piston was seizing up multiple times. I'm surprised the compression numbers and bore scoping look good.

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