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  1. #1

    Breakthrough! Adjustable Blow-Off Valve

    Adjustable BOVís to get from the stock boost level of about 10 psi to 11.3/11.4 range that Kawi advertised are now available. Price: $0.

    The only catch? A bit of work is required.

    First remove the plastic BOV (the one on the I/C). NOTE: Use a heat gun on the ribbed black outlet hose and it will practically fall off by itself. The alternate way is to pull very hard on it until it breaks as several other people have done Ė then you get to buy a new one.

    Now the secret: the BOV looks like a single plastic piece but it is not. It is a 2-piece unit. Heat the round domed top with a heat gun until very hot. I then used a thin silicone kitchen hot pad to grip the top, rock it back and forth with some force and it slipped right off.

    BEHOLD THE SIGHT OF A FULLY ADJUSTABLE BOV MECHANISM!

    To adjust: while holding the 10mm bolt head on the seat end of the valve, remove the 10 mm nylock that was under the cap you removed. Remove the bolt and slide out the brass tube the bolt went through. Then remove the 21mm nut. The hollow shaft the 21mm nut was on is slotted. Turning the shaft clockwise increases the spring pre-load and thus the blow off pressure and vice versa.

    Iíll make a block-off plate this weekend with an air inlet fitting and an air pressure measuring fitting to set mine at the proper pressure. Hopefully someone in the PWC aftermarket business will offer this service to you guys. If not, Iíll consider doing so even though Iím in a different business.

    The result should be virtually undetectable unless Kawi admits they never sold a ski that hits the advertised boost level. If someone familiar with Kawi sealers can ID the sealer used on the BOV top, it will be undetectable. The sealer (black in color) is not silicone and appeared to me to run out of the joint under high heat.

    Enjoy!

    Dave


  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Ok so how do you seal it back up?

  3. #3
    Upon further review/inspection and with the clarity only a couple of self-congratulatory cocktails can bring, I think it is black silicone and that the small glob I thought ran out when heated (it was on the inside of the BOV body) was just where a small amount of silicone was squeezed out when the BOV was originally assembled.

    In any event, the fit is so tight it would probably be fine with just about any sealer.
    Last edited by DaveF; 04-10-2007 at 10:18 PM. Reason: add info

  4. #4

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    Interesting. From what I read, you have not tested it yet to see if the adjustments you are suggesting will actually get us where we need to be, right?

    Thanks.

  5. #5
    I have not tested yet. But I am 100% certain we can get well over the 11.5 psi setting needed for stock and likely well over the setting needed for any over-boost condition created from aftermarket S/C pulleys. There is quite a bit of adjustment and just 2 turns on the adjuster made a difference that could be easily felt by hand and I suspect is way over the 11.5 setting needed. There are several turns available beyond that.

    I plan to fab the pressure measurement rig and set the BOV to 11.5 to 12 psi this Saturday and test the ski Sunday. I'll post results.

    I think it will be important for the pressure measurement rig to be more than a small block-off plate. Rather I am thinking a chamber of some sort to provide some air volume and get the source of air pressure away from the valve will provide better results. I have some simple, cheap ideas I"ll share once proven.

    Normally I would not have made the initial post until after testing but the discovery that the stock BOV's are adjustable amazed me enough to want to share it immediately.

  6. #6

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    very good idea, please keep us post. Thanks

    Calvin


    Quote Originally Posted by DaveF View Post
    I have not tested yet. But I am 100% certain we can get well over the 11.5 psi setting needed for stock and likely well over the setting needed for any over-boost condition created from aftermarket S/C pulleys. There is quite a bit of adjustment and just 2 turns on the adjuster made a difference that could be easily felt by hand and I suspect is way over the 11.5 setting needed. There are several turns available beyond that.

    I plan to fab the pressure measurement rig and set the BOV to 11.5 to 12 psi this Saturday and test the ski Sunday. I'll post results.

    I think it will be important for the pressure measurement rig to be more than a small block-off plate. Rather I am thinking a chamber of some sort to provide some air volume and get the source of air pressure away from the valve will provide better results. I have some simple, cheap ideas I"ll share once proven.

    Normally I would not have made the initial post until after testing but the discovery that the stock BOV's are adjustable amazed me enough to want to share it immediately.

  7. #7
    I guess everyone is assuming it leaks. The manual states it shouldn't open until 12.18 psi. So if it leaks at 10.x psi, it is a malfunction valve.

  8. #8
    Been around for years...seen it all Kawi-Guy's Avatar
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    Nice work !!!

    Way to go, we have a breakthrough!

  9. #9
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Quote Originally Posted by creativepuzzle View Post
    I guess everyone is assuming it leaks. The manual states it shouldn't open until 12.18 psi. So if it leaks at 10.x psi, it is a malfunction valve.


    Or like he said, It needs adjustment.

  10. #10
    Been around for years...seen it all Kawi-Guy's Avatar
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    I'm going outside now to remove mine !!
    Let's hope I don't break it

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