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  1. #1

    well, it blew up :(

    So i just finished doing the top end on my 94 sl750 and repairing the cases after the holes for the craddle bolts ripped out (see other thread) and took it out and ran it a few times.

    The thing was screaming and running fantastic asides from a little porpoising and pushin 42 mph, where normal was 29 before the rebuild.


    The plugs looked a little thin after first run so i put the restrictor back in the return that i forgot, stuck new plugs in, and ran it all day and burnt probly 15 gal. of gas thru it with out a hiccup. Now the fun part, i took it out again after work the other day and it was running for about 8 minutes and was absolutely screaming and then it went quiet. Clicks when you press the starter, and is locked up tight.

    So i got home and pulled the heads and the cylinders/jugs look BEAUTIFUL. I preasure tested it before install and it held 7 psi for 10 min. and im sure ive got no leaks. However, the plugs in that five minutes ALL leaned out pretty bad. With the pump disconnected I gan get about 3/4 of a turn from the crank and it locks up. I dont think it was a lean sieze as the cylinders are perfect but i cant figure it out.


    Any thoughts? im considering parting it and just buying a newer/bigger ski but thats pricey, but i also dont have the time or energy to pull the engine out again and see what popped in the bottom end.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    I did not re-read your previous build thread.

    How 'used' was the bottom end? Was it carefully inspected before the new top end went in?

    I know it can be depressing when an engine lets go. I just finished rebuilding a 1200 motor with a failed crank bearing (180 hours since new).

    The upside is that pulling an engine for the second time goes much faster. You know how to do it and the bolts are not going to be corroded in place this time.

    Since the top end is still good condition you also know exactly what needs doing. A crankshaft rebuild. Several options there, including SBT (did I just say that?)

  3. #3
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by K447 View Post
    Several options there, including SBT (did I just say that?)
    I didn't see nuthin shultzie

  4. #4
    the bottom end was beautiful, no slop, no play in the rods, no rough spots, and thats why my head is spinning. The only thing i could have seen changing is that now that the engine if actually bolted into the ski, the pump alignment is off. Metal was removed from the bottom of the cases in order to repair the damage from the bolts, and although the shims went back in the exact same way they came out, could that few thousandths of an inch of metal screw up the alignment to the point of putting excesive bind on the rear bearing?

    What ever it was that let go is def. in the pto side because i can hear and feel it stickin. If my fuel upmp failed could it cause the lower end to run w/o oil/fuel and smoke a bearing, but leave the top end unharmed? Also, it is converted to premix.

  5. #5
    and are the cranks rebuildable in these things? SBT is kinda iffy.....

  6. #6
    BlueFishCrisis's Avatar
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    Quote Originally Posted by 87r View Post
    and are the cranks rebuildable in these things? SBT is kinda iffy.....
    Rebuildable, yes. In your garage, no. Need a specialized shop with the right equipment.

  7. #7
    what kind of costs/ where would i find bearings at for them. Are the rods interchangeable as well im guessing? where would i find those?

    Sorry for the newby questions ive just never done bottom end work on pwcs before

  8. #8
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    Send the crank out to a shop that specializes in 2 stroke cranks. A SBT crank can be had for about 300 bucks. Your bearings could have very well had rust in them. Its hard to tell if they are any good without pulling the crank out of the case. I had a 1200 crank recently that felt great in the cases, but when I pulled it out, 6 of the 8 bearings were bad, and 2 of those 6 were really bad. You probably had a bearing that was on its way out, and finally decided to let go.

    By the way, that ski should top out at about 48MPH

  9. #9
    BlueFishCrisis's Avatar
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    Quote Originally Posted by BryanP View Post
    Send the crank out to a shop that specializes in 2 stroke cranks. A SBT crank can be had for about 300 bucks. Your bearings could have very well had rust in them. Its hard to tell if they are any good without pulling the crank out of the case. I had a 1200 crank recently that felt great in the cases, but when I pulled it out, 6 of the 8 bearings were bad, and 2 of those 6 were really bad. You probably had a bearing that was on its way out, and finally decided to let go.

    By the way, that ski should top out at about 48MPH
    Definitely have a shop rebuuild, or go with SBT. I wouldn't trust used cranks on Ebay as they go for $200-300 anyway.......

  10. #10
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    I had my 1200 crank done through John Zigler. Came back beautiful with high quality parts.

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