Results 1 to 10 of 10
  1. #1

    SLX 780 wierd compression numbers.

    I recently got a 95 slx 780 with a burned magneto harness. Before I sink the money fixing the magneto stator I performed a compression test first to make sure the engine was good. I pulled the plugs, put a tea spoon of 2 stroke oil in the spark plug holes, spun engine over for a few seconds, installed the compression gauge and got. 135, 150, and 250. I took it one more time and got 135, 150, and 250. That is mag, center, and pto. The cylinder that had high compression seemed to have more oil in it than I put in. Just for curiosity I checked my running slx and got 125, 125, 130. What can cause one to have real high compression?


  2. #2
    David Drkvampire2001's Avatar
    Join Date
    Jul 2011
    Location
    Edgerton, Wisconsin, United States
    Posts
    2,857
    +1
    30
    first of all, you did not check compression correctly, you do not OIL the pistons before a compression test. also you need to hold the throttle WIDE OPEN, then crank

  3. #3
    LaveyT's Avatar
    Join Date
    Jul 2008
    Location
    Cincinnati
    Posts
    672
    +1
    10
    If you got 250 psi I would crank the excess fluid from your cylinders, Hydrolock.

  4. #4
    I was holding the throttle wide open. Just forgot to mention that. And this ski has been sitting for 8 years so I didn't want to chance scoring a cylinder up or breaking a ring.

  5. #5
    So I just need to spin the engine some with the plugs out and clean the cylinders?

  6. #6
    David Drkvampire2001's Avatar
    Join Date
    Jul 2011
    Location
    Edgerton, Wisconsin, United States
    Posts
    2,857
    +1
    30
    Correct, but hold the throttle open while doing it, no reason to do a wet test

  7. #7
    David Drkvampire2001's Avatar
    Join Date
    Jul 2011
    Location
    Edgerton, Wisconsin, United States
    Posts
    2,857
    +1
    30
    oil the ski up today, then do the test tomorrow. but also remember while the ski might have been sitting for 8 years, a little oil you put down the plug holes is not going to save it if its going to blow, 6000+ rpms will blow up an engine thats not perfect..fast..

  8. #8
    Ill spin it over tonight when I get home and redo the compression test.

  9. #9
    Thanks for all the help.

  10. #10
    David Drkvampire2001's Avatar
    Join Date
    Jul 2011
    Location
    Edgerton, Wisconsin, United States
    Posts
    2,857
    +1
    30
    No problem! we where all new with skis at one time! im still learning!

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. My completed SLX 780 project.
    By Hayabusa in forum Polaris Open Discussion
    Replies: 13
    Last Post: 08-18-2010, 09:02 AM
  2. Replies: 18
    Last Post: 08-07-2010, 12:27 AM
  3. Does a 95 Sl750 have the same number of veins as a 96 slx 780?
    By gvnitup in forum Polaris How To & FAQs
    Replies: 4
    Last Post: 05-28-2007, 12:05 PM
  4. 96 SLX 780 No Spark
    By Truckinevan2005 in forum Polaris Open Discussion
    Replies: 4
    Last Post: 04-30-2007, 10:02 PM
  5. Rode an SLX 780 all weekend...
    By javiert99 in forum Polaris Open Discussion
    Replies: 8
    Last Post: 09-05-2006, 11:52 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
  •