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  1. #1
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    Burned up piston cause???

    07 200hp Yamaha HPDI
    273 hrs
    Took my dad out fishing and spent 4-5 hrs idling/trolling (never got on plane) and drove fine no issues. Next trip out noticed speed had fallen off and was making ticking noise along with sneezing while idling. Thought it might have been a bad coil since the original plug looked like it was running super rich on 1 cyl. Changed out plugs and a new coil then went out night fishing. Everything was good fired right up no noise, idle was smooth ran around 3-4k rpm like normal then last run back to the ramp tach said 5k but I know I wasnt going that fast and then she shut off on me and locked up. Pulled the head and found the aftermath. Installed new powerhead and got the injectors flowed now jsut covering my bases to not kill this one anytime soon..

    What do you guys think. when looking at the motor from the rear its the second one down (middle) Locator pins came loose, bad injector, bad fuel,heat, oiling issue???

    20210401_153013.jpg 20210401_175750.jpg20210227_173130.jpg
    Last edited by Will I Am; 04-12-2021 at 10:37 PM.

  2. Member
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    #2
    Detonation is my guess. Can be caused by many things. By themselves or in combination with others. That model is noted for being sensitive to it.

    Does not look as bad as many. Maybe just that one cylinder can be cleaned up.

  3. Member
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    #3
    Same thing happened to my motor. Same year and HP as yours. Hydrotec said locator pin, and that it was very common on these motors. Nothing I did or didn't do that caused it. It was going to happen no matter what, just a matter of time.

  4. Member
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    #4
    Seems that the locator pin would be long enough so that it would hit a cylinder wall before it could come out far enough to let a ring rotate.

    Has anyone ever pulled one out to see?

  5. Member
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    #5
    Quote Originally Posted by yam911 View Post
    Seems that the locator pin would be long enough so that it would hit a cylinder wall before it could come out far enough to let a ring rotate.

    Has anyone ever pulled one out to see?
    It will scar wall. The hole it's pressed in will get egg shaped and allow it lay down enough for ring to turn. I had a customer boat that I checked compression on and the #2 was 15# lower than others. I pulled it apart and found the egg shaped pin hole with ring turned. Caught it before the ring caught Port. Starting with the #1 cylinder going to #6 the pins got progressively tighter as I went from top to bottom. #6 wasn't loose at all. #1,2,3,4 fell out in my hand. #5 was easily pulled out with pliers. Replaced all pistons and rings and it's still running good.

  6. Member
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    #6
    Other than a ring trying to turn and contact the pin, pushing the pin sideways, what others forces could be at play? What force could there be that tries to move the pin outward?

    Pins moving outward on their own accord has me baffled. Granted there is a lot going on within a piston and cylinder.

    What is different about HPDI pistons, pins and rings that is so different from all of the other Yamaha pistons, pins and rings that don't seem to suffer as much?

  7. Member
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    #7
    Only guess I've ever had is the harmonics of engine. That's only a guess. Zero proof.

  8. Member
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    #8
    i'll pull the piston out tonight and see if we can get a clue of what happen

  9. Member
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    #9
    Quote Originally Posted by Will I Am View Post
    i'll pull the piston out tonight and see if we can get a clue of what happen
    Excellent. I was about to ask you to do that for us. Please take a look at the pin for any evidence of the pin being extended beyond the OD of the piston and/or the pin scraping on the cylinder wall.

    While you are at it, would you take note of the position of the pin with reference to the intake and exhaust ports? I am guessing that it is positioned so that if it did come loose and extend that it would not catch on a port.

  10. Dink Flipper alpine4x4's Avatar
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    #10
    Looks like detonation or lack of oil to me. Your crank case is dry as a bone. If it was the pin you usually see missing pieces of piston around the exhaust port. I just rebuilt my #1 cylinder due to pin failure. The pin was intact, but had wallowed out the hole enough the rung spun, caught the exhaust port, and ripped the top of the piston off. My crank case was still lubed up unlike yours. Be curious to see what you find!
    06 Skeeter 20i Yamaha 250 HPDI
    Visit my Youtube Channel!
    https://www.youtube.com/channel/UCW6p06navSpOqUn3xotG2vA

  11. Member
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    #11
    I question the lack of oil in that cylinder too. My guess is that after the first symptoms I got I continued to run it after I changed the coil and plugs thinking is was ok. Compression was 120psi but that cylinder had let go or pieces of the cylinder and piston got stuck in the reed causing the sneezing. Then heat took over????

  12. Dink Flipper alpine4x4's Avatar
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    #12
    Quote Originally Posted by Will I Am View Post
    I question the lack of oil in that cylinder too. My guess is that after the first symptoms I got I continued to run it after I changed the coil and plugs thinking is was ok. Compression was 120psi but that cylinder had let go or pieces of the cylinder and piston got stuck in the reed causing the sneezing. Then heat took over????
    Maybe. I ran mine for around 1/4 mile wide open after the rpm drop and then idled another 1/2 mile back to the launch. My reeds were caked in piston material, but I experienced no issue from it I recognized. Based on what I saw with the hoses on the intake I'd say you should probably have still had oil going into the crank case. Mine only generated enough heat to burn the oil out of the cylinder.
    06 Skeeter 20i Yamaha 250 HPDI
    Visit my Youtube Channel!
    https://www.youtube.com/channel/UCW6p06navSpOqUn3xotG2vA

  13. Member
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    #13
    What did the rings look like in the other cylinders? Did they have normal carbon buildup or excessive? I ask as the rings can get too much carbon, then it's like a rock. It can cause resistance and heat to build up on the cylinder walls which causes the cylinder walls to starve for oil. Then as the heat builds up the oil begins to thin out and keeps it from staying on the rings as they are designed to do. Depending on the carbon on the rings would help if possible or not. Looking at the crank it appears the heat travelled from the cylinder wall down the connecting rod to the crank. As others mentioned could have been caused by the locator pin coming loose and creating drag and heat buildup.

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    #14
    Quote Originally Posted by yam911 View Post
    Other than a ring trying to turn and contact the pin, pushing the pin sideways, what others forces could be at play? What force could there be that tries to move the pin outward?

    Pins moving outward on their own accord has me baffled. Granted there is a lot going on within a piston and cylinder.

    What is different about HPDI pistons, pins and rings that is so different from all of the other Yamaha pistons, pins and rings that don't seem to suffer as much?
    Running leaner? Ski doo had a issue with all of their etec 800 sleds when first released with detonation loosening the locating pins. The mountain sleds would let go around 1500 to 2k miles as they were highly loaded. The trail sleds could go 8k + before coming apart. Skidoo replaced the topend on mine and a bunch of others in a recall to stop the problem. The etecs are very lean running and I am betting was part or most of the issue. Cj
    2002 X19 200HP OX66 HO Vmax,HPDI lower, it lives, thanks Hydro Tec.

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    #15
    Correct me if I'm wrong Oil enter at intake after throttle body on to the crank and to all cylinders at same time. Oil pump failure would leave all bearings and cylinders dry. Oil mix in Vast then lube on top of piston / cylinder through injectors.
    Main lubrication comes from bottom and through transfer ports to the sleeve / piston.
    My 250HPDI did the same but happened at 6000rpm looked much worse than that.
    Luckily my trawling motor batteries were still full.

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    #16
    One of the locator pins looks weird. I'm thinking oil problem based from all the heat in the end of the rod but also piece of trash could have gotten in the rod bearing causing the heat too. Hopefully someone looks at this as sees something I'm missing and can provide a a better answer.
    20210421_235904.jpg20210421_235928.jpg20210421_235838.jpg20210422_000052.jpg

  17. Member
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    #17
    I would say the bottom end gave way first that were the piston / bore score come from. Maybe a cap bolt or the bearing first. Luckily those rings did not open that could have been a block.
    Sad news as is. Now its time to open it up 250 / 300

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    #18
    Looks like rod bearing failure due to lack of oiling. Clogged oil passage? Any of the other journals look bad?

  19. Member
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    #19
    If it is lack of oil how to explain all of those pits in the top of the piston and the buildup of aluminum from the piston on the spark plug?

  20. Member
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    #20
    Those pit marks is from shrapnel getting squashed in the Squish Band and they get there through the transfer port.
    If it was run for longer some more pistons would have shown squashed (PIT) marks.
    Been there...... got 2xHPDI 250
    You guys are fine all spares on your door step try that here....AFRICA

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