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  1. #1

    95 sl 650 sludge blowing out of intake and outlet... What is it?

    I just rebuilt carbs, re-piped fuel lines, new fuel, new oil, new triple fuel pump, etc. on a 650 that hadn't run in 7 years. I've flushed the cooling system and when I ran it on the trailer, some black oily slime blows out of the outlet. Yesterday, I took it to the marina for its maiden water test and I noticed a couple of things:

    1) From front to back, cylinder 1 was warm, 2 was cold, and 3 was hot. I'm suspecting spark plugs, but I installed new plugs for all of my bench testing thus far. Don't know if they can foul up that quickly, but I will pop a new pair in and check.

    2) It idles fine, but when I gave it throttle, it wouldn't get faster that 10 mph.

    3) When back on the trailer, I gave it throttle to clear it out and a bunch of black slime came out again. I cleared it out again at home and more black out the back and a greyish slime came out of the intake area.

    What could this be, why is it happening, and how do I make it stop? Any ideas on the cylinder issue?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What intake are are you referring to? The jet pump intake grate under the hull?

    It is common for the waterbox to accumulate oily black exhaust residue, especially if the engine has not been running properly or has been running at low speeds or extended start and stop testing. Once you get the engine running properly and on the water at speed it should clear out.

    See my signature links for some common maintenance items.

    You may need to trim the spark plug wires back about 1/4" and reattach the spark plug boots. It is common for the wire ends to fray and make poor connection to the small threaded spike inside the plug cap.

    When you rebuilt the carburetors did you use genuine Mikuni rebuild kits? Checked the pop-off pressure?

    Are you using the correct NGK spark plugs?

    Initial water test should be done on the trailer, strapped down front and rear. Back down the launch ramp, then run it with the seat off. You can stand beside it and apply throttle as needed for testing. Be sure to set the parking brake on the tow vehicle.

    No need to remove it from the trailer until you are sure it is running properly.

  3. #3
    Intake as in jet pump intake grate under the hull. I thought it was weird that gray slime came out of there.

    I will be trimming the wires. When I rebuilt, I did use mikuni rebuild kits, not aftermarket. I checked popoff press...all 3 @ 18psi I am using BR8ES.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by FlynRyn79 View Post
    Intake as in jet pump intake grate under the hull. I thought it was weird that gray slime came out of there. ...
    You may want to remove the jet pump and inspect. Through-hull bearing seals may have dried out. There is grease inside the through-hull bearing assembly. These can be rebuilt using commonly available seals. Size info via my links, in the jet pump section.

    Also inspect the jet pump impeller bearings for looseness, gritty feel or grinding noises. Should be smoothly rotating, no slop. If you don't trust the impeller stub shaft seals, remove the tail cone and inspect. Should be zero moisture and zero rust in the rear bearing.

    Or just go ahead and rebuild the stator bearings and seals. Better to know it is good than to risk destroying the impeller when the bearings go bad at speed.

  5. #5
    Thanks for the advice...looks like I have a new weekend project on my hands!

    I understand why cylinder 2 could be cold, but why is #1 warm and #3 hot? They are both getting fuel, air, and spark, but why a difference in temps?

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by FlynRyn79 View Post
    Thanks for the advice...looks like I have a new weekend project on my hands!

    I understand why cylinder 2 could be cold, but why is #1 warm and #3 hot? They are both getting fuel, air, and spark, but why a difference in temps?
    Was this on the water or on the trailer?

    If on the water, perhaps some spark plugs are firing more intermittently than others.

    If the cylinder heads have been removed at some point, it is possible that the cylinder head gaskets were reinstalled incorrectly and are now blocking some of the water cooling passages.

    Another possibility is that there is sand or silt accumulated inside the engine water cooling jackets. If this has occurred, you get to take the engine apart to clean it out. Reverse flushing just does not seem to be aggressive enough to actually get the stuff out once it has settled in.

  7. #7
    on the water. So I need to take the heads off and clean out the little spaces along the inside of the cylinder walls?

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by FlynRyn79 View Post
    ... So I need to take the heads off and clean out the little spaces along the inside of the cylinder walls?
    First get the spark plugs firing consistently. That may be all it needs.

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