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  1. #1

    1993 Yamaha waverunner III

    I have a modified sled. Factory pipe, DG waterbox, ocean flame arrestor, mild porting. All this was done back in 1996 by a PWC mechanic. I was young and foolish to say the least. After all these mods were done, the sled lost speed after 20 minutes of riding. 38 MPh down to 27-28 MPh. I knew I was only going to get a few MPH with all this done. Also had a brain box mod which was removed and somehow mechanic put it back to stock (dale did mod on brain box) since that time nobody can give me a straight answer why I loose top end of my power. After seven years in storage, I took it out for a run. Fresh gas, new plugs, and a new battery. She ran top, balls out (38-39 mph) and then bog city. No change. Rebuilt carb (needle and jets were not replaced). Resulted in quicker off the line response. If I don't let go of the throttle from initial take off, she will not bog. After a week or so, I'm back to twenty minutes. With more knowledge now, I know now it is the carb. I'm going to do a compression test to started how the engine is doing. This power loss issue seams to happen to a lot of sleds with the minkuni carb. I read a lot of info about replacing this or that and using the old springs on the adjusters. I need solid information to resolve this issue. I'm sure the guys over at group K would know exactly the issues or at least know what to ask. Thanks in advance for any info.

  2. #2

    Join Date
    Aug 2006
    You may want to check all the fuel lines, fuel on-off switch, and pickup in tank, kinda sounds like it is starting to starve for fuel after a while.

  3. #3
    Thanks. I pushed around 10 psi through the breather intake below the engine hood latch and through the entire system and caused fuel to spring from my primer lines. Hoping this would clear any debris. I read that after full throttle and stopping causes carb to drip fuel and run rich and you loose your top end speed. Does changing the the needle valve and also the jets cure these issues?

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