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Thread: 96 sl780 help

  1. #1
    zacharyobuchowsk's Avatar
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    96 sl780 help

    I have a 96sl780 that was running fine up untill last weekend, I was riding along just fine and all of a sudden the rpms dropped to 700. So I shut it off to check underneath for weeds or anything and none was found. It would not start for another 20 mins or so after I shut it off, when It finally started up it was really load and almost has a knocking sound. The sound, sounds like it's coming from the front left of the engine. All cylinders have compression and there's no issue with the spark. It is currently at ideal of 17-1800 rpms. But sounds horrible. Anyone have any tips? I was thinking it was something with the front fly wheel, I have an extra engine for parts, but don't wanna start replacing stuff when I don't know what is broke. Thanks for the help!


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    You may have a broken connecting rod bearing. I suggest you remove the cylinder head and inspect.

  3. #3
    zacharyobuchowsk's Avatar
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    I did that, all is fine. I think it's the clutch set up for the starter to the fly wheel. Sound about right?

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    BlueFishCrisis's Avatar
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    Could be a failed starter bendix. Unfortunately quite a bit of work to get to the part. You would be able to see more by removing the flywheel cover. May have to slide the fuel tank to get at the cover. It's always easiest to pull the motor for this kiind of repair. If the bendix is bad, the flywheel will need to come off. You will want to check the condition of the teeth on the flywheel too. Remove the timing plug ontop of the flywheel housing and shine a light in there. You may be able to see some debris and confirm the issue.

    If it is a bendix issue, I am surprised the motor will still start......

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by zacharyobuchowsk View Post
    I did that, all is fine. I think it's the clutch set up for the starter to the fly wheel. Sound about right?
    Can you turn the engine over by hand?

    Remove all spark plugs. Remove cover from driveshaft coupler. Grab coupler in hand and turn. Listen for noises or gritty feel. You are turning the engine and the impeller.

    There will be magnetic resistance as the flywheel magnets move around the stator.

  6. #6
    zacharyobuchowsk's Avatar
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    I pulled the fly wheel cover last night and the  bendix... Which is the part the starter engages to the fly wheel, seems wore down and stays stuck in the forward position... I believe that is where al the noise is coming from. I pulled the same part out of a spare engine. Once I put the new part on I'll let ya know how it goes, thanks for the help

  7. #7
    BlueFishCrisis's Avatar
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    Make sure you have both thin steel washers on the bendix, one on each end.

  8. #8
    zacharyobuchowsk's Avatar
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    Okay thank you! I didn't think to check that I will be switching part tommrow, wish me luck!

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    Well it's been awhile for me, but I've found my problem..the first cyclinder piston (closest) to the mag was destroyed and broke into pieces, the rod bearing is gone so I'm assuming that's why the pistion was in peices. I'm unsure of why this happened though. I never changed the oil pump over to pre mix so that's how I think all this happened? Any other good ideas? So on to my next concern, I want to fix this especially seeing as the body and paint have just been redone last winter..with that being said is it better to try to rebuild the crank shaft and replace the bearing in the first cyclinder rod or buy a new crank? This will be my first rebuild and after reading the forms and the manual I see there's alot that I need to check and watch for, while I have the engine out I plan to replace the oil and fuel lines, use a pre mix instead of the pump, I'm debating on over hauling the carbs and im going to bore the cyclinders and use over size Pistons and rings... Any other advice or tricks Ya have will be greatly appreciated! Thank you

  10. #10
    zacharyobuchowsk's Avatar
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    Click image for larger version. 

Name:	image.jpg 
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ID:	352716This is what the piston looked like

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