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Thread: Thar She Blows

  1. #61
    SeaLion's Avatar
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    Took it apart one more time. Meticulously cleaned both cylinder and head and also the modified head gasket. There was a little build up I didn't notice before on all 3. Didn't seem like it was bad enough to cause the leaking but I spent a good 2 hours cleaning everything up. Put new o-rings even though I put new ones in there prior. Torqued heads in proper sequence. Let everything dry for 2 days and took it on the water this morning. Same damn leaks. I torqued the nuts to 22 ft lbs. and same thing. At this point I told my boys I'm gonna go run it on the river anyway. I couldn't resist anymore lol. It was either going to impress or blow up. I wanted to find out which. Let me say that it was every bit the rocket I remembered it as. So light and nimble. Turned on a dime. I held it wide open almost the whole time on the several test runs. 6950 to 6990 max rpm which I seem to recall it was running in that range before too. Yes my MFD was working. I unplugged it and plugged it back in and disconnected and reconnected the battery and it all of a sudden worked. Even my fuel float was working. I didn't stay long with the water spraying and right at and near the intake but I just had to ride it. Glad I did. It brought back fond memories. I also noticed I have a small crack and leaking water into the hull the pump bolt insert is on the exhaust side. Came home and decided to do a compression check and I had 145 psi in all 3 cylinders. There is nothing wrong with this engine. I am 100% certain now that the mystery bb or ball has been in there in the crankcase the whole time and it finally made its way up from the way the kid was vertically riding and bouncing it and revving it to the moon. The bb bouncing around the head smashed the plug and closed the gap and stalled the ski. The bottom end never gave out. Now I don't understand this darn leaking around the studs and head nuts. It's not getting into the combustion chamber because every time I took it apart to redo there was no water in there. I can fiberglass the hull crack and leak I just discovered and not worried about that. I gotta figure something out for the head nuts leaking and squirting. That's a new one to me. I would really like to keep the modified head set up but if I have to go back to a stock head and head gasket I will. Anyone have 780 heads? I have 1mm over bore. I can't recall if stock heads will work or if they will have to be reshaped anyway for the larger bore. Getting there and I'm not ready to give up on it yet. Riding it even for a short time this morning has light the fire to ride this ski again.

  2. #62
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Honestly. I don't think new heads would stop the water leaking around the studs. I'm not sure why your head nuts are not sealing the water in. I have a set of specialty nuts for my PSI cylinders. They're like the factory cap nuts, but they have a countersink drilled into the bottom of them. Supposed to make a better seal or something.

    Only other suggestion I have would be those sealing washers I mentioned previously.

    https://www.mcmaster.com/standard-washers

    Pressure-rated metal bonded sealing washers.

  3. #63
    SeaLion's Avatar
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    I thought maybe the modded head gasket and head combo is not sealing properly and letting water through that makes its way up through the studs and out from under some of the nuts. It can't go past the o-ring that seals the combustion chamber. Thanks for the link for the washers. Which one is preferable? There are quite a few different types there. How does this affect torque of the nuts?

  4. #64
    Moderator beerdart's Avatar
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    Ive use copper crush washers as well as the bonded ones with good results.


  5. #65
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    So this leaking thing is not a big deal? All my years I have never seen it or come across it but it seems like a few of you have the same issue at the head nuts. I'm back in Cali for a week or so and will try to track something down to take back home with me and try. I wish I could get just a couple and try it to see if it really works for my situation before ordering $50 of washers. Anyone know the size of the studs on the 780 or the thread sealing washer size I need. Those say they can re reused but I imagine crush washers are a one time use.

  6. #66
    I like Boobs. wetwolf's Avatar
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    Quote Originally Posted by beerdart View Post
    Ive use copper crush washers as well as the bonded ones with good results.
    +1 on this.

  7. #67
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    Hey Bruce! I'm gonna try some copper 5/16 or M8 washers and see how it goes. I need to change the name of this thread to Thar She Goes now.

  8. #68
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Sweet, Should be able to find copper crush washers pretty easily and cheaper.

    We love to see old polaris back on the water.

  9. #69
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    I'm back in L.A. and have spent the better part of the day looking for copper crush washers and no one has them. I found a copper washer kit at Harbor Freight actually looking for somethng else. Will these solid copper washers work? Kit had 5/16 in there that I could use. I'm assuming since it's solid copper it will still conform and seal. My next problem is that I am out of O-rings I had bought extras from back 15 years ago. Couldn't find the O-rings either anywhere to have spares on hand. I bought them originally from Pep-Boys and they had it in their pull out bins in 3 packs. Haven't been in one in about 10 years and they have totally reorganized everything and don't have the selection of O-rings like they used to. So now I'm afraid to remove the heads since I don't have any more O-rings. Would it be okay to just remove the leaking nuts one at a time and put the copper washer and retorque? I won't be back home to the ski until Saturday and will keep looking but if L.A. places don't have this stuff I doubt my little town of Bullhead City would have it.

  10. #70
    Moderator beerdart's Avatar
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    Yes one nut at a time no need to pull the head. McMaster has the washers and o-rings.
    Quote Originally Posted by SeaLion View Post
    I'm back in L.A. and have spent the better part of the day looking for copper crush washers and no one has them. I found a copper washer kit at Harbor Freight actually looking for somethng else. Will these solid copper washers work? Kit had 5/16 in there that I could use. I'm assuming since it's solid copper it will still conform and seal. My next problem is that I am out of O-rings I had bought extras from back 15 years ago. Couldn't find the O-rings either anywhere to have spares on hand. I bought them originally from Pep-Boys and they had it in their pull out bins in 3 packs. Haven't been in one in about 10 years and they have totally reorganized everything and don't have the selection of O-rings like they used to. So now I'm afraid to remove the heads since I don't have any more O-rings. Would it be okay to just remove the leaking nuts one at a time and put the copper washer and retorque? I won't be back home to the ski until Saturday and will keep looking but if L.A. places don't have this stuff I doubt my little town of Bullhead City would have it.

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