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  1. #1

    Need Help with 780SLT (fuel delivery??)


    Short Version:
    Rebuilt 780SLT top end.
    Ran great.
    Had issues with base gaskets, pulled the cylinders and replaced, ran great again but only for a couple of hours.
    Now it starts up after a couple of pumps of the throttle and seems to idle ok but it bogs down and sputters when you give it some throttle. It started by bogging just a little from the hole shot and then it progressed to bogging and sputtering throughout the rev. range. It was occasionally clear up for a few seconds and then go right back to doing the same thing. It acts like it's not getting enough fuel. I rebuilt the pump when I did the engine, carbs, and lines. I added a clear, in-line fuel filter when I did the rebuild and it has fuel in it so I don't think there is an issue in the tank. Is there a way to test the pump (a pressure or volume test I can run)? It's a 1997 780SLT with the triple outlet pump. It looks like it has a restrictor built into the end of the fuel rail. I DID not put a restrictor in the return line. I don't think that applies to this model from what I have read on the forum.

    Thanks for the help.


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Put a fuel pressure gauge between the fuel pump and a carb.

    Should see around 1-2 psi at idle and 4-6 psi at WOT.

    Do not put it AFTER the carbs because you DO have a restrictor built into the rail. So the pressure is before that.

  3. #3
    Well....the problem does not appear fuel pump related. I rebuilt the pump again and did the check from the Clymer manual. I do have fuel coming out of the return line so I guess I should be OK. I'm starting to think this is electrical. Can anyone give me any common problems that would cause bogging down, rough idle, no power and generally be OK at light throttle.....maybe a slight intermittent miss at light throttle.

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