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  1. #1

    Baught HX need advice

    Hi all, I just baught a HX that as a Factory Pipe on it, Rossier intake manifold (pre-mix), Square shape aftermarket spark arrestors and maybe carbs (did not mesure them yet)

    I tried it Tuesday for the first time on a lake but there was 3-5 feet waves so I did not try it as much as I would of liked and the HX is a bit hardcore since its my first Ski.. did jump a few feet in the air though

    On thing I noticed is it runs like a tuned banshee, weak torque at low rpms but when you get to 6800rpm + its pulled crazy ! Like a raped ape !

    I got a few questions,

    - since this Ski seems like a retired racer and I want to use it only recreational, should I install a stock pipe to regain the fun torque ?

    - somone told me since it only had about 130psi compression I could shave the head a bit to regain compression and torque as a result

    - Would an APE pipe be more suited for just having fun ? I am not after full out speed

    - Is there any mods I could do to make it more recreational ? I saw UMI steering but hard as hell to find !!

    - Prop change to give me more accel to have fun around ? good idea ?

    - I ordered parts to but it back to injection since I find pre-mix annoying (smoke etc) and costly $ for nothing. what you guyd think ?

    Thank you in advance for your advices I really appreciate


  2. #2
    flyin' the friendly skies airbornexp's Avatar
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    Quote Originally Posted by PLF View Post
    Hi all, I just baught a HX that as a Factory Pipe on it, Rossier intake manifold (pre-mix), Square shape aftermarket spark arrestors and maybe carbs (did not mesure them yet)

    I tried it Tuesday for the first time on a lake but there was 3-5 feet waves so I did not try it as much as I would of liked and the HX is a bit hardcore since its my first Ski.. did jump a few feet in the air though

    On thing I noticed is it runs like a tuned banshee, weak torque at low rpms but when you get to 6800rpm + its pulled crazy ! Like a raped ape !

    I got a few questions,

    - since this Ski seems like a retired racer and I want to use it only recreational, should I install a stock pipe to regain the fun torque ?

    - somone told me since it only had about 130psi compression I could shave the head a bit to regain compression and torque as a result

    - Would an APE pipe be more suited for just having fun ? I am not after full out speed

    - Is there any mods I could do to make it more recreational ? I saw UMI steering but hard as hell to find !!

    - Prop change to give me more accel to have fun around ? good idea ?

    - I ordered parts to but it back to injection since I find pre-mix annoying (smoke etc) and costly $ for nothing. what you guyd think ?

    Thank you in advance for your advices I really appreciate
    I assume that someone put a 787 in this ski? if yes then definitly take the specII off. if you are around 130psi you are ok but sounds like almost time for a top end job. run it till it goes. it should be around 150psi. maybe even higher with that head. if you can find a coffman pipe or a neptune or a spec one you will be ok. there is no problem putting the oil injection back in...i actually prefer it but others will disagree. its all preference and or peace of mind really. If this ski is tuned to the hilt you should take a look at the prop and see what it is. it may be too tall if you start taking HP parts off. I am curious what carbs you have on it. if they are buckshots you might as well take this thing back to stock and ride it.

  3. #3
    Quote Originally Posted by airbornexp View Post
    I assume that someone put a 787 in this ski? if yes then definitly take the specII off. if you are around 130psi you are ok but sounds like almost time for a top end job. run it till it goes. it should be around 150psi. maybe even higher with that head. if you can find a coffman pipe or a neptune or a spec one you will be ok. there is no problem putting the oil injection back in...i actually prefer it but others will disagree. its all preference and or peace of mind really. If this ski is tuned to the hilt you should take a look at the prop and see what it is. it may be too tall if you start taking HP parts off. I am curious what carbs you have on it. if they are buckshots you might as well take this thing back to stock and ride it.

    When your talking about 787 you mean big bore/stroker kit ? And what is a specII ?

    sorry I am have few knowledge of ski's I have a 400whp eclipse and modified 400ex and I share a 2009 speedster 155 with my father but am totally new to 2 stroke watersports.

  4. #4
    flyin' the friendly skies airbornexp's Avatar
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    Sorry, originally the HX came with a 720cc motor. it had a vertical motor meaning the cylinders are vertical. if it has a 787cc motor(slanted to the right looking at it from the rear) someone customed the motor mounts in there and shoehorned this motor in there. if it is the 720 I would leave the Factory Pipe on it as that pipe really woke up the 720's. if its a 787 Factory Pipe (FPP) Factory Pipemake a Spec I and a Spec II. the spec I was just the lower chamber and some water injection. the Spec II was the full exhaust. this was for racing only and loved to eat pistons if it wasnt running flat out and tuned for the 30min to hour race then it would have to be retuned. (trust me I tried this)

  5. #5
    Ok did some research and it does not look like a 787, the cylinders are straight up and there is no provision for the oil pump on the magneto cover.

    - I lokked at tips to take compression and realized I took it on a cold engine, I will plug the hose in and retake it in the proper way.

    - How hard, how long is it to change pipes on this machine ?

    - While searching there are many places that say that the factory pipe is not supposed to make you loose torque and others that say it does.. ??

    - does a prop change make that much of a difference on bottom end grunt ?

    Thanks

  6. #6
    AquaGuy's Avatar
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    It does not matter if you checked compression on a cold or warm engine. 130 is low. You are looking for 145-150. That is where your loss of power is coming from not the Factory Pipe. Sounds like you need a top end job. A 720 with a Factory Pipe pulls great.

  7. #7
    Quote Originally Posted by AquaGuy View Post
    It does not matter if you checked compression on a cold or warm engine. 130 is low. You are looking for 145-150. That is where your loss of power is coming from not the Factory Pipe. Sounds like you need a top end job. A 720 with a Factory Pipe pulls great.

    Thank you for the explanation, is it normal that it pulls like crazy at high rpm even with the loss of compression, well my question is mainly; does loss of compression affect mostly bottom end torque

  8. #8
    kecheme's Avatar
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    Quote Originally Posted by PLF View Post


    I got a few questions,

    - since this Ski seems like a retired racer and I want to use it only recreational, should I install a stock pipe to regain the fun torque ?
    In stock form this ski slow out of the hole...
    - somone told me since it only had about 130psi compression I could shave the head a bit to regain compression and torque as a result
    I would recheck the compresssion myself first before I put a top end in it.
    - Would an APE pipe be more suited for just having fun ? I am not after full out speed
    Yeah the APE pipe runs great for rec setup .
    - Is there any mods I could do to make it more recreational ? I saw UMI steering but hard as hell to find !!
    If want torque keep the factorypipe, check the water injection system for that pipe, check compression again. Repitch the prop.
    - I ordered parts to but it back to injection since I find pre-mix annoying (smoke etc) and costly $ for nothing. what you guyd think ?
    All my ski still use oil injection after 14 years it still works.
    Thank you in advance for your advices I really appreciate
    My 2 cents in bold.

  9. #9
    If I get everything straight on it, what size prop should I get ?

  10. #10
    kecheme's Avatar
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    Quote Originally Posted by PLF View Post
    If I get everything straight on it, what size prop should I get ?
    If want to rip your arms off. Like to jump waves. Slimline 15/20 from Skat trak and the bigger pump cone.

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