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  1. #1
    yamxlt1200nj's Avatar
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    Fast Idle Runaway

    I had my ski out yesterday for 2hrs for the first ride of the season and it ran great. Didn't get a chance to flush it yesterday so I had it on the trailor to flush it today and it was running a fast idle (~3k rpms) so I killed it. I noticed it was a little fast yesterday in the water (1700-1800 rpms) even with the idle screw almost completely out. I cranked it up again and the engine revved and would not shutdown even after I hit the kill switch and pulled the lanyard. Just before I was about to panic I blipped the throttle and it stalled. Did some work on the ski this past winter and I'm afraid I may have an airleak and want to hear some opinions. Here's the work I did over the long winter.

    - Replaced the bearings in the intermidiate housing and pump since I had to replace my driveshaft. Splines stripped and had me stranded.
    - Replaced the fuel lines, oil lines and fuel cock
    - Since I had to remove the exhaust for the bearing housing I decided to also pull the carbs and rebuild them as well (used Mikuni kits and pop off tested 82 psi synced). Everything is bone stock and I did not disturb the highs and lows.
    - I lost a locating pin on the exhuast and thought it dropped down the manifold so I pulled all three jugs to make sure it was not in the case (btw it was not in the case but had to look)
    - Used new OEM base and head gaskets.
    - I did not pressure test after I installed the jugs, head and exhaust / intake manifold (This is a cardinal sin I know)

    I'm really nervous I may have an airleak so I talked to Lowell today and bought a pressure test kit from him. I'd like to hear some opinions on what could have caused the fast idle and the engine runaway besides an airleak. After the runaway I unscrewed the idle screw so the throttle was completely closed but it was still idling at 2500-3000 rpm

    One more thing, Last summer I rebuilt the top end and replaced the crank shaft(pressure test was good last summer)


  2. #2
    WATER WOODY's Avatar
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    Air leak.... get the motor pressure tested, pressure test kits from Lowell Horning. Keep us posted.

  3. #3
    yamxlt1200nj's Avatar
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    Kevin, thanks for the reply. Test kit from Lowell is on it's way.

  4. #4
    WATER WOODY's Avatar
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    Call me if you have any issues...775-315-0222

  5. #5
    yamxlt1200nj's Avatar
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    I just finished a pressure test and I don't think it's positive. It losses about 1 psi per minute and then holds steady at 4 psi over 10-12 minutes. I sprayed the gaskets with Windex and I can't see any bubbling. Is it time to pull the engine for a closer look?

  6. #6
    WATER WOODY's Avatar
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    Im up Brian....775-315-0222

  7. #7
    yamxlt1200nj's Avatar
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    Found a leak at the rear crank seal on the inside diameter.

  8. #8
    yamxlt1200nj's Avatar
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    How bad is this?

    # 1 piston rod shows heat marks at the crankshaft. The others are spotless but # 1 shows excessive heat at the bottom of the rod. I found an air leak at the inner diameter of the rear seal....Holds pressure all day but only up to 4 psi. This is a new crank with about 10 hrs on it. Could this have happened when it ran away on me? It ran away for about 5 secs before I choked it.
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  9. #9
    yamxlt1200nj's Avatar
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    Think I found the reason for the heat marks and partial root cause to my issue. Front oil seal was missing spring on the inside which got caught up in the bearing...I don't think I'll be using aftermarket seals any longer especially since it was only 10 hrs old. When you compare aftermarket to OEM you can tell the variance in quality. Just my 2 cents...

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