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  1. #1
    johnsonmtz's Avatar
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    Fuel Hose Length

    Okay, ha ha.........he said hose length Now that we have that out of the way, I actually wonder if length does matter

    I'm gathering plans for the spring check-up on the SLT780 and I'm trying to recall some of the quirks I need to address. Last year I had the carbs dialed in as best I could but when I looked at piston wash it still seemed as though MAG was getting just barely enough fuel, CEN was just about right, and PTO was rich.

    When I ran through the fuel system a few years ago I replaced everything with 1/4" Fuel Injection rated hose. Then last year I put a fuel pump rebuild kit in my OEM triple outlet pump. So, as far as fuel supply to the carbs goes I should be in great shape.

    Over the winter I've been thinking what else I could do to even out fuel delivery. Then it dawned on me: When I replaced all the fuel lines I made the hoses from the pump to each carb as short as possible. So, this means PTO will have the shortest hose and the hose for MAG is about 50% longer.

    Should the length of hose to each carb be equivalent to provide the same amount of friction/backpressure in the line? Is it possible my variable length hoses are causing my problem, or is there still something in the carb tuning that I've missed? I've been inside and out on these carbs, pop-off is right where it needs to be, jets are the right spec (everything is stock), and needles are all set.

    One other thing that bugs me a bit is my primer line. I have it T'd into the supply line between the fuel shut off and the fuel pump. It always seems that after I ride, the primer line is no longer full of fuel and whenever I use it I have to pump the plunger several times to fill the line and feed fuel to the carbs. Do these primer plungers have check valves in them? I wonder if I'm possibly getting air into the fuel supply and that's part of the problem?

    The ski seems to run just fine and usually it runs on the rich side at idle. I think in reality I'm fouling the PTO plug at low speed and it has to blubber and fire until it clears out when I take off. It seems that these symptoms wouldn't point to having air in the fuel system so maybe the primer deal isn't a problem.

    I dunno. I'm open for suggestions.

    KJ


  2. #2
    Race, wreck, repeat delagem's Avatar
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    As far as the primer line, I always understood that the "T" should be placed in the return line. This way, if your primer develops a leak, it won't provide a place for air to enter, and lean out your carbs.

    When I installed mine, I put a loop in the return hose, with the "T" at the low point, so there's always a bit of fuel sitting there, to assure that the primer always has a bit of fuel to draw from.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Open the link in post #32. It says to install the primer "T" into the return line.

    http://www.greenhulk.net/forums/show...=108712&page=4

    I suspect this is to prevent any chance of air entering the fuel system throught the plunger. Just like Delegem said. Which does have a check valve by the way.

    The fuel pump outlet hose lengths shouldn't be an issue.

    Make sure the PTO carb isn't dribbling when at idle. (fuel leaking past the needle and seat will cause a rich condition) Remove the F/A and look down the carb when running.

    Make sure the carbs are all in sync. (opeing all the same amount at the same time)

    If you went through the carbs afew years ago, you may want to open them up again and look for debris or "varnish" forming. (I didn't say rebuild, I said go through them if you rebuilt them a few years ago)

  4. #4
    johnsonmtz's Avatar
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    Quote Originally Posted by xlint89 View Post
    Open the link in post #32. It says to install the primer "T" into the return line.
    Whoops. Didn't know that. I guess I'm lucky I haven't burnt things down. Which post #32 are you talking about? I looked in the tech section but didn't see anything specific to primer installation.

    Quote Originally Posted by xlint89 View Post
    The fuel pump outlet hose lengths shouldn't be an issue.
    I didn't think so either, but it's the only thing that comes to mind. UNLESS, I am getting air in the lines dues to my stupid placement of the primer T. But like I said, it's rich at low RPM, so that wouldn't seem like I'm getting air in the fuel stream. I think I'm going to make them all equal length just to eliminate the possibility.

    Quote Originally Posted by xlint89 View Post
    Make sure the PTO carb isn't dribbling when at idle.

    Make sure the carbs are all in sync. (opeing all the same amount at the same time)

    If you went through the carbs a few years ago, you may want to open them up again and look for debris or "varnish" forming.
    Needles and seats are new, carbs were opened last year and checked for junk and pop-off tested (and passed).

    Delagem: When you say a loop, do you mean you just leave the return line extra long so it sags and put the T at the bottom of the sag?

    KJ

  5. #5
    Race, wreck, repeat delagem's Avatar
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    Quote Originally Posted by johnsonmtz View Post
    Delagem: When you say a loop, do you mean you just leave the return line extra long so it sags and put the T at the bottom of the sag?
    KJ
    Yes, exactly. Doesn't need to be a full loop, just a low spot. Because if it's installed in a high spot, and you park your ski for a few days, that fuel will make it's way back to the tank, and your primer will have no fuel to work with.

    I've installed 5 primers this way, all work great.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by johnsonmtz View Post
    Whoops. Didn't know that. I guess I'm lucky I haven't burnt things down. Which post #32 are you talking about? I looked in the tech section but didn't see anything specific to primer installation.

    The link above ^^^^^^



    Sorry, forgot to add it before.

  7. #7
    johnsonmtz's Avatar
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    Quote Originally Posted by xlint89 View Post
    The link above ^^^^^^



    Sorry, forgot to add it before.
    No problem, I just looked at the thread again and saw the link. I thought for a second I might have just been a dooffus and not seen the obvious.

    Thanks for the info on the primer 'T' placement guys. I guess changing the location of the T will be one of the first things I do. When I first noticed the primer line was dry I looked around to see if I could find a brass or stainless check valve to put in the hose to prevent it from siphoning. Placing it in the proper location will eliminate that need

    KJ

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