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  1. #1

    More Pro 785 Questions

    First question is, I finally got it running after long battle of numerous problems (one after another) but Im not sure about the valves.I havent had it much over an idle or even on water yet,the valves dont seem to be moving not sure if they kick in after xxxx amount of rpms or what?Im not to sure about the mechanics of the valves.
    Second question is the trim doesnt seem to be working,havent looked into it yet.
    And thirdly the MFD doesnt work at all no clue at all on it,will other makes like 780 and 750 work on it as long as its same design?I know my son has sl750 and hes says they have the same MFD shape available form it.


  2. #2
    jcjw1998's Avatar
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    Ok,
    I just went through all the same issues with my pro 785. First, those valves don't ever look like they move. I have seen them both while running on the trailer and while running in the water. No worries there. Second my trim only works when the ski is in the water. I actually just went out in the garage to test that and it is true. The trim does not seem to work while out of the water. Last and most important, you need to have a working MFD of you can experience many issues. I had an MFD that did not work and my ski would not run at all when on the water. One of my freinds asked me why the MFD did not work and I told him I didn't know. He opened the electrical box and found the fuse missing. We replaced the fuse and the ski immediately ran perfectly. We found that the ski will tend to stay in "Limp Mode" when the MFD was not working. The fuse you need is a .5 amp/250 volt FYI. It is about an inch long or so and you can buy a box of 5 at Radio Shack for $1.99. That should answer your questions! Also, cant wait to hear what you think once you get that thing out on the water... mine is deadly fast!!

  3. #3
    jcjw1998's Avatar
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    "And thirdly the MFD doesnt work at all no clue at all on it,will other makes like 780 and 750 work on it as long as its same design?I know my son has sl750 and hes says they have the same MFD shape"

    And yes, in those year models the MFD are interchangable.

  4. #4
    Moderator beerdart's Avatar
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    The valves open aprox 5000 rpm's so you will not see them open out of the H2O they do flutter when you rev. A 750,780 mfd will work. My guess is the 1/4amp fuse is toast.

  5. #5
    Ill check it out and see if it might be the fuse.What would happen if the valves arent working ,would it run but not to its full potentual?

  6. #6
    jcjw1998's Avatar
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    Yes, check the fuse before getting into more complicated problem solving. These things are notorious for blowing the MFD fuse. Also, the exhaust valves MUST be functioning for the motor to run. When the engine is running on the trailer is exhaust coming out of the back of the ski? If so, the valves are working. You just cant see them under the rubber boots.

  7. #7
    Yea exhaust is coming out the back and it does run,its got a fresh top end rebuild.Its been a pain getting it to this point,Ive bought 1 piston a set of rings,starter,bendix,it basically was in parts when I bought it.Sad thing is im about to the end of riding season,Im thinking about giving it a fresh coat of paint in off season.

  8. #8
    Moderator beerdart's Avatar
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    Quote Originally Posted by jcjw1998 View Post
    Also, the exhaust valves MUST be functioning for the motor to run. When the engine is running on the trailer is exhaust coming out of the back of the ski? If so, the valves are working. You just cant see them under the rubber boots.
    Not true the motor will run if the valves are closed. The valve changes the exhaust opening size @ 5K rpm and above. if the valves do not open the top end will suffer but the bottom end take off will be normal. A quick check is to wire the valves open and let it rip to see if you ge full RPM.

  9. #9
    bowsniper's Avatar
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    If your on land and you rev the engine , they should all be moving up at the same rate. they will go up about 1/2 inch and some fluttering like beedart said. check the tension on the cables first. see if theres slop. take that out. that could prevent them from opening properly. there procedures for testing it electricly if need be..

    punch it,, if it jumps out of the water and the bow rises like crazy, your fine, they work, if it falls on its face and boggong when ya hit it, they arent opening. assuming carbs are set correctly and everything else is working perfectly.

    The trim will work while running only. you'll know once its running in the water,, while idling, trim up and the bow will break the surface, when down, the nose will dig into the water a little. You can see the difference in the wash behind the ski too. and of course you can check it while running, stay at 1 speed and try the trim. you will notice the difference.

    Or if at the dock, get it idling and trim it up. stop the motor and look at where the nozzle is, up or down, then start it back up, go the other direction on the trim and see if the nozzle changed positions, then youll know before you leave the dock.

    Other MFDs will work but, the trim is twice as fast on the pro as a 750sl's trim motor. so the gauge will not show accurate trim settings. you need a pro 785 mfd for it to work perfect.

    My ski has NO mfd and runs perfectly.. just a tiny tach, although, I'm going to install one. they have lots of info for the rider. 14 different items. clock,tach,speed,distance counter,hot,power,lowoil,gas level, oil level,top rpm,battery voltage,trim setting,total distance and hours.

    It's a 1/4 amp fuse and they are a bitch to find. I ended up going to a ma and pa hardware store and they had it. lowes didnt. when they blow, they look exactly the same. no tell-tale signe of a burn inside the glass. only ohming them are the only way to tell if its blown.

    your gonna be trippin when you punch it and see what that ski can do! lol Hold on! sounds awesome in the water. Mine jumps out of the water and the midrange is crazy fast. just a quick blip and your doing 45.lol. and lots of horsepower left!

    The exhaust valves move in conjunction with the rpms. thier movement is regulated by the cdi. it tells the servo motor how much to push or pull (it really doesnt push or pull, the motors gear sits on a flat gear and slides it back n forth)). idle.....closed...wot.....open all the way.

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