Page 1 of 2 1 2 LastLast
Results 1 to 10 of 13

Thread: Thunk!

  1. #1
    1996 SL900 & SL700 turk0004's Avatar
    Join Date
    Jul 2007
    Location
    Chicago IL
    Posts
    328

    Thunk!

    Hi fellas. A friend of mine was bringing my SL900 back to the landing last night and looks like the bilge is busted. By the time he was done riding he said that it "died". My brother in law towed him to the landing and there was a lot of water in the hull, and about half way up the crank coupler. Pulled it out of the water and pulled the petcock. Pulled the plugs and tried to turn it over and just got a thunk.

    Got it back home and pulled the pump, hoping it might be a bearing or something but no, would not turn over (by hand). Pulled the domes and lot of water in there. After about another hour or so, I tried to turn over by hand again and I was able to. I tried the starter and it turned over nicely but I could tell there were a couple of "rough" spots while rotating. I assume my next step is to pull the intake manifolds and take a peek at the crank, but my question is...what am I looking for exactly? I will also check the crank index, but my assumption is that even if the index was out, it would turn over nice and freely, but again that is only my assumption.

    So I will peek at the crank and hope one of you can tell me what I am looking for AND please if there is something else I need to be checking other than crank index.

    Thanks,

    Turk


  2. #2
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Location
    Campbell, Ca.
    Posts
    14,100
    +1
    105
    If you suspect the electrical box may have water in it, split it before the water can do its thing there and pay particular attention to the bottom of the board. You're looking for water and/or rust.

    I have a feeling you won't have to check much more than the crank index to see the extent of your damage...but just in case it's still in phase, you need to get all the water off the crank and bearings. Displace the water with oil and run it ASAP so that it can warm up and get that water out of there.

  3. #3
    1996 SL900 & SL700 turk0004's Avatar
    Join Date
    Jul 2007
    Location
    Chicago IL
    Posts
    328
    Checked the index and it's out less than 1mm. I am not for sure of the tolerances on this measurement? I measured with the heads off and pistons exposed, brought the mag to TDC and from what I have read, both the CEN and PTO should have the exact same measurement (I measured from the piston to the top of the jug). Let me know if this sounds like either an improper way of measuring or if the .5 to 1 mm are enough off to call it a day on the crank.

    How would I displace the water with oil? How do I get oil into the crankcase?

  4. #4
    seaobin's Avatar
    Join Date
    Jun 2007
    Location
    Raleigh, North Carolina, United States
    Posts
    1,573
    +1
    1
    turk

    You can pour down the intake. Remember in a 2 stroke, first compression is in the the crank case, then into the cylinder.

    There are 3 plugs that let you drain the crank case. They are below the exhaust manifold and are 10mm bolts. Pull them out and spin the motor withthe plugs out. Pour some oil into the crank and spin it again while draining. This will coat the crank as well as helping to get the water out.

    After the oil drains out, repalce the plugs and rebuild. Try to start. Running the engine till warm will allow the rest of the water to evaporate out

  5. #5
    1996 SL900 & SL700 turk0004's Avatar
    Join Date
    Jul 2007
    Location
    Chicago IL
    Posts
    328
    Ok, I pulled the drain plugs but found them on the intake side. They were 8mm brass plugs under each of the 3 manifolds. BUNCH of water came out of there. Put the plugs back in and poured oil into the manifolds. Now the motor is very easy to turn by hand . I will leave it like that overnight and drain that oil out tomorrow, rebuild everything and see if it starts.

    Does anybody know if about 1mm of difference between the two pistons when one is at TDC within clearance?

    Anything else I should be doing?

  6. #6
    100 MILES OF HEAVEN AND I AM SMACK IN THE MIDDLE KEYZBUM's Avatar
    Join Date
    Apr 2007
    Location
    JUST NORTH OF CUBA-- FL,KEYS
    Posts
    2,556
    +1
    39
    pm sent
    mattman

  7. #7
    PolarisNut's Avatar
    Join Date
    Dec 2006
    Location
    Lower Michigan
    Posts
    1,809
    Quote Originally Posted by turk0004 View Post
    Does anybody know if about 1mm of difference between the two pistons when one is at TDC within clearance?
    Thats not an accurate enough way to check crank index. It will give you a rough idea and let you know if you have a bent rod or not. Sounds close enough that it should start though.

  8. #8
    1996 SL900 & SL700 turk0004's Avatar
    Join Date
    Jul 2007
    Location
    Chicago IL
    Posts
    328
    Big thanks going out to mattman for the phone conversation about my problem last night (about 2am his time i think). Drained the oil I put in the crankcase last night, reassembled everything, poured a little oil down the carbs and sprayed a little starting fluid while cranking and started right up . Been starting it, letting it warm up, allow it to cool for about a half hour, then did it again and again and again most of the day (dry wall in my garage now has lots of oil on it). Starts up perfectly, idles perfectly, revs up perfectly...i think i'm gonna be alright.

    Thanks again to the great forum!

    Turk

  9. #9
    100 MILES OF HEAVEN AND I AM SMACK IN THE MIDDLE KEYZBUM's Avatar
    Join Date
    Apr 2007
    Location
    JUST NORTH OF CUBA-- FL,KEYS
    Posts
    2,556
    +1
    39
    GLAD TO HEAR
    But you still need to cheak the index --there is a real test somewhere in the tech section
    It will still run with an out of index crank till it burns down a piston
    ??did you do the throttle/choke thing????heheheheh
    mattman

  10. #10
    1996 SL900 & SL700 turk0004's Avatar
    Join Date
    Jul 2007
    Location
    Chicago IL
    Posts
    328
    Quote Originally Posted by KEYZBUM View Post
    GLAD TO HEAR
    But you still need to cheak the index --there is a real test somewhere in the tech section
    It will still run with an out of index crank till it burns down a piston
    ??did you do the throttle/choke thing????heheheheh
    mattman
    Oh yeah, did the choke thing a bunch. Checked the index with degree wheel as described in the manual page 4.111 (it was a bitch). Index is perfect. Just an FYI, I also measured the center and pto depth from the spark plug hole with mag at TDC and center was 1.59mm shorter than pto and index was exactly 120deg between all at .100 ATDC, again per manual.

    Thanks again for the help!

    Turk

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. SC thunking at certain RPMs?
    By imp0ster in forum 4-Tec Performance
    Replies: 33
    Last Post: 03-01-2013, 06:20 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •