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  1. #1

    HX with Westcoast head, 44's, twin pipes, etc...JETTING???

    Hey all, just got my 1996 HX running and in the water. It has a Westcoast head (160psi compression), dual redtop 44's (I believe their 44's but dont know how to verify), FPP twin pipes (not sure what they are from, but they have been modified), MSD box, R&D intake manifold, etc.

    I rebuilt the carbs and observed 20psi pop-off pressure on both carbs, and jetting was 95/135 and 107.5/135 with low speed adjustment at 2 & 1/4 turns out and high speed at 1/8 turn out.

    The ski runs like garbage. It will idle in the water for about 30 seconds and then die, and requires using the primer to get it started again. It runs great midrange, but bogs out and dies if you attempt anything over half throttle. Sometimes I feel the high jets kick in for a second or two before the bog out. The bogging is worse with the flame arrestors on.

    I attempted to open the high speed adjustments to 1 full turn out and it seemed to come alive a little better top end for a second or two before bogging out again.

    Im not sure if it isnt getting enough fuel to the carbs, or if the high/low speed adjustments are off, or if it might need a rejetting?

    Any suggestions are greatly appreciated, thanks!


  2. #2

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    well as far as I know no 720 hx ever had twin pipes,jetting sound like to fat -can ya take some pix of motor might be 800 or 951
    also you might try installing fuel pressure gauge and see if starving at speed
    but pix would be nice

  3. #3
    flyin' the friendly skies airbornexp's Avatar
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    Quote Originally Posted by chip View Post
    well as far as I know no 720 hx ever had twin pipes,jetting sound like to fat -can ya take some pix of motor might be 800 or 951
    +1 the only twin pipes FPP made was for the 951. plus ive never seen 44mm carbs on a 720. sounds like a Frankenstein boat that was built by someone that had no idea what he was doing or it was some heavily modded CC race boat

  4. #4
    I'm not familiar with Red-Top's or a Dual Pipe set-up on the 717 but my previous FFP'd HX w/ Mikuni 44's had the following Jetting.
    This was a fully Ported (Cases and Juggs) engine--

    Total Jetting==>247.5//252.5


    Main=120 MAG 125 PTO
    Pilot=127.5~130
    N&S=2.0
    80 Gram
    P-OFF=21~22
    LS=1 1/2
    HSM=3/4
    HSP=1

  5. #5
    Thanks for the replies guys. I forgot to mention that the needle and seats are 2.5's. Also, another friend looked at the carbs and thinks they may be 38's, but we dont know either way and dont know how to verify the size? Also, Im not sure why the previous owner would have put these jets in the carbs to begin with? I plan on getting the jetting FPP recommends and going from there.

  6. #6
    flyin' the friendly skies airbornexp's Avatar
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    you can get a cheap micrometer from auto zone to check the throat size on the carbs....good luck with the FPP rep. If the same B$#@! works there answering the phones you wont get much. all she will do is tell you to read the directions if you have them or not and she is extremely snotty about it.

  7. #7
    Quote Originally Posted by airbornexp View Post
    you can get a cheap micrometer from auto zone to check the throat size on the carbs....good luck with the FPP rep. If the same B$#@! works there answering the phones you wont get much. all she will do is tell you to read the directions if you have them or not and she is extremely snotty about it.
    ..... they still haven't changed, even after all these years. Talk to Ross Liberty (owner) if he's in a good mood you *might* get somewhere with him--but only on his product. Personally, I've never heard of "twins" on a 717 but I guess there's still some whacky hardware out there left over from the Fischetti '90's

  8. #8
    44's look *nothing" like 38's---For starters, the Throttle Body has both High Speed and Low Speed Adjusters on the same side.
    The 44 also has both Throttle Rods linked together with a Coupler instead of the 38's Linkage Bar. Just Google Mikuni SBN44mm and SBN38mm,, plenty of Pix out there.....

    2.5 sounds way too big for a 717 engine

  9. #9
    Tool Bag water worx's Avatar
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    Quote Originally Posted by TurboLs1 View Post
    I plan on getting the jetting FPP recommends and going from there.
    Factory Pipes jetting is NOT even close....good luck with that one.

    Hope you have a LOT of $ to buy pistons when it blows up. Modding a 720 is like playing russian roulette.

  10. #10
    Chris03HD's Avatar
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    Post a pic of the twin pipes.
    Only twins I ever saw in the 1990's for 650/720's was made by PSI.
    I had a set..

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