Results 1 to 9 of 9
  1. #1

    Join Date
    Aug 2014
    Location
    Northeast TX
    Posts
    91

    94 - SLT 750 - replace seals or not?

    Creating new thread as old one is basically dead.
    Hole in PTO piston. Did vac leak test. Lost one inch of vacuum in 30 mins. That is apparently acceptable.
    Fuel pump has been upgraded. Auto cock deleted. All lines replaced. Restrictor is in return line.
    Carbs rebuilt with all mikuni stuff. Synchronized using drill bit method.
    All these were replaced PRIOR to the hole in the cylinder. Still have found no smoking gun.
    I put the new piston in last night so I could check the crank twist. Book says to put mag cyl at TDC and check the other two. Didn't make sense to me so I put the cen cyl at TDC and checked mag and pto cyls. They were within .02" of each other. I can only assume that is acceptable.
    The biggest question I have is this:
    When I bought the piston, I went ahead and got the full gasket set. It came with crank seals. Since I have the engine out, should I replace them since I have them? I really didn't want to split the case, but if I should then I will. Just looking for some expert advice please.
    I'm really hoping it was the cheap carb gaskets that I used after I rebuilt them...
    Any help would be great.
    Thanks in advance,
    BL


  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Location
    Newman Lake, WA
    Posts
    2,479
    +1
    186
    Yeah... it's tough to not find a smoking gun on an engine failure. I have the same story as you on a '95 SLT 750 I serviced. Did all the right things (triple pump, rebuilt carbs, leak test, new plugs, gaskets, etc... then melted down a piston on break-in (PTO maybe?). I never figured out for sure what caused it. I suspect a leaking carb base gasket but don't really know. So, like you, I replaced the piston/cylinder/head and double checked and re-cleaned everything. Ski runs great now and has for a season. Good, cause it's a neighbors ski... but I'm still nervous about what happened there.

    **correction to original post**
    Splitting the cases on the blue 'Fuji' engines can be done w/o messing with the cylinders or pistons. See BFC's details below. This makes replacing crank seals a pretty straight forward job... so I would recommend it. Then you know they are good.

    A valid point is this. The existing crank seals might have a couple more good years in them before they start to leak. New ones would hopefully have a couple 20 good years (like the originals). So I can see why most folks here always do complete rebuilds. Tough call.

    Cheers!
    Last edited by ripcuda; 06-23-2015 at 01:26 PM. Reason: correction

  3. #3
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    5,040
    +1
    143
    Quote Originally Posted by ripcuda View Post
    You can't really split the case easily without pretty much dis-assembling the whole motor. You have to unbolt the cylinder bases to free up the lower case studs to separate. That's pretty much a complete rebuild at that point.
    While your recommendation to keep the seals in because the motor is well sealed is valid, I just want to point out that the only thing holding the case halves together and the bolts on the bottom side of the crankcase. The cylinders can remain in place, as can the pistons, heads, and water rail. I have pulled a motor to perform a crank seal replacement this way.

  4. #4
    ripcuda's Avatar
    Join Date
    May 2010
    Location
    Newman Lake, WA
    Posts
    2,479
    +1
    186
    Ah.... whoops. You're right BFC. I was confusing the blue 'Fuji' and the red 'Domestic' engines. The domestic's have the cylinder studs in the lower case holding it all together. The fuji's do not.

    In that case... I change my recommendation. As BFC has stated... you can flip the motor upside down and unbolt the lower case... remove it, clean case halves, install new crank seals, re-seal cases and rebolt it all together without "unsealing" the cylinders or messing with the pistons. Sounds like a good easy option to me. (Wish domestics were as easy).

    Thanks for setting me straight BFC!

    Cheers!

  5. #5

    Join Date
    Aug 2014
    Location
    Northeast TX
    Posts
    91
    Ok now I didn't know I was actually that close already. Yeah, I'm definitely doing that. The thing is, I don't mind pulling all heads and jugs. All the gaskets came in the kit so I don't see the harm. If it's a bad idea to mess with what's working then I won't.
    Is there anything weird to know about changing these seals?
    and can I use a good automotive silicone to reseal halves?

  6. #6
    ripcuda's Avatar
    Join Date
    May 2010
    Location
    Newman Lake, WA
    Posts
    2,479
    +1
    186
    See BFC's awesome Fuji engine rebuild thread... all you need to know
    http://www.greenhulk.net/forums/showthread.php?t=193805

    Threebond 1211 is a crowd favorite engine sealant. I like Threebond 1184 (tad runnier, less caulky, cheaper, works good). Others have used Permatex sealants too. Just needs to be oil/gas resistant.

    Cheers!

  7. #7

    Join Date
    Aug 2014
    Location
    Northeast TX
    Posts
    91
    so I am curious, why only put 1211 in the bottom of the case where the seals go instead of both top and bottom?

  8. #8
    ripcuda's Avatar
    Join Date
    May 2010
    Location
    Newman Lake, WA
    Posts
    2,479
    +1
    186
    I skim coat the seals all the way around with sealant (1211)... and just apply sealant to only one side of the cases since they sandwich together.

    Cheers!

  9. #9
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Location
    Medina, Ohio, United States
    Posts
    5,040
    +1
    143
    Quote Originally Posted by ripcuda View Post
    I skim coat the seals all the way around with sealant (1211)... and just apply sealant to only one side of the cases since they sandwich together.

    Cheers!
    Yep me too....

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Replies: 4
    Last Post: 07-07-2016, 08:26 AM
  2. 94 SLT 750 will not start - need help!!!!!
    By aleal in forum Polaris How To & FAQs
    Replies: 8
    Last Post: 05-24-2008, 08:52 PM
  3. 94 slt 750 fuel question
    By ace16a in forum Polaris Open Discussion
    Replies: 3
    Last Post: 07-08-2007, 11:10 PM
  4. 94 slt 750 problems
    By ace16a in forum Polaris Open Discussion
    Replies: 17
    Last Post: 05-28-2007, 03:45 PM
  5. '94 SLT 750...deal or no?
    By Fish Man in forum Polaris Open Discussion
    Replies: 5
    Last Post: 04-22-2007, 09:46 AM

Posting Permissions

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