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  1. #1
    XSKIER's Avatar
    Join Date
    Apr 2009
    Fenton, MI

    '97 1100 stx: will only turn 6100 rpm

    This machine was brought to me in march disassembled and previously estimated by another mechanic. The mag end piston, rod and bearings were shot form lack of oil. The owner wanted to get a little extra performance out of it, so I suggested overbore, F/As, and a solas prop.
    I found: 2 gal of water in fuel tank. Cracked injection lines. Corroded carbs. Cooling system full of sand. Wasted stock impeller.
    So, I: Overbored 2mm, Three new pistons, replaced rod and bearings, pulled the fuel tank and cleaned, cleaned lines and selector valve, overhauled the carbs, and replaced the injection lines.
    The first trip out with stock jetting, I did not stay in the throttle long as the machine would rev about to 6K and then loose rpm, making me think it was way lean, I then would blip the throttle, cycling the accel pumps, and gain a little rpm. So I jetted up, down, changed props, changed f/a back to stock, went through carbs over and over, and I can't find any thing wrong. Good wash and plug color on the mag piston, but not on the center and pto pistons. They are clean, with no carbon what so ever. Still maxes out around 6000 rpms.
    Yesterday I checked the crank index, and it is right on. Checked the ignition timing, right on. Checked the compression, even. Checked the plug caps, right on. So I went to test again, and could only get 3000 rpms out of it. Trigger coil tests good, ignition coils test right at the top end of the allowable range, there was some corrosion on the regulator/rectifier terminals. What else can I test in the ignition system?
    By the way, I had a '98 stx come in the same week with exactly the same problems and rebuilt it, and has been tearing up the lake for the last month... I had already delivered this one back to the customer, before I could start switching ignition components.

  2. #2
    btldigger's Avatar
    Join Date
    Feb 2007
    lebanon tn.
    If your sure its running on all 3, ie all 3 plugs are hot when running I would check out the pump bearings. Mabe they are bad and loading the motor down so bad it wont rev. You may have already checked that but its a thought.

  3. #3
    i have a 1998 stx 1100 here, runs bad. out of the water on the trailer it'll rev to 8000 rpms, if you hit it hard off the start , it'll bog for a second, and may die, though once it catches it's strong. In the water, she'll only get to about 5600 rpm max, and that is a slow acceleration, and then drop to approximately 3000rpms. let go of the throttle and try again, she may raise to 5500rpm. I've taken the carbs apart, and cleaned them, also new spark plugs. checked the rear control box, no water in it, and no signs of corrosion. Any ideas??? thanksss

  4. #4
    1998 stx, I taken apart and cleaned carbs, replaced fuel filter, and fuel lines. Now i run a max 0f 6150rpms, any ideas what else to check? can it be a bad fuel pump?

  5. #5
    could bad reed valves cause this, what are the symptoms of bad reed valves?

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