Page 1 of 4 123 ... LastLast
Results 1 to 10 of 31
  1. #1
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3

    '96 Sltx- bad PTO piston again...thoughts?

    Bought with a bad PTO piston. Did a complete rebuild including crank bearings, seals, carbs, new piston. 4 hours later it happened again.

    Looks like it is getting enough lubes. Didn't seize. What are your thoughts or experiences?




    Click image for larger version. 

Name:	20200715_141908.jpg 
Views:	33 
Size:	42.8 KB 
ID:	464445


  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    42,569
    +1
    2,176
    What did you do with the fuel system? Full carburetor cleaning and rebuild with OEM kits?

    New fuel hoses, OEM fuel filter?

    Fuel selector valve, water separator?

  3. #3
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3
    > Full clean
    > Aftermarket kits
    > removed and cleaned fuel tank
    > removed and cleaned water separator
    > inspected lines
    > cleaned and inspected on/off valve
    > new pulse lines

    Other two cylinder plugs are honey brown.

    Also upgraded ignition. To me it looks like pre-detonation.??

  4. #4
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3
    Click image for larger version. 

Name:	20200416_182004.jpg 
Views:	29 
Size:	56.2 KB 
ID:	464446

    Original piston - same PTO cylinder

  5. #5
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    42,569
    +1
    2,176
    Quote Originally Posted by ValleyRacer2 View Post
    ...
    > inspected lines

    > new pulse lines

    ... looks like pre-detonation.??
    Hmmm. Can you check the crank for correct phasing?

    To create the conditions for detonation, something mechanical has to be not right. Are the cylinder heads stock, not high compression?
    All three heads are the same?
    What gasoline octane was being used?

    ‘fuel hoses inspected’ - Upgraded from the original gray Tempo fuel hoses, correct?

    Correct spark plugs?

  6. #6
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3
    Crankshaft was completely rebuild by a very experienced machine shop that does a lot of 1050s. Grey tempo lines are gone all newer reinforced lines.

    Stock heads
    BPR8ES plugs
    87 octane
    Premixed

    Gotta be either air getting in, low fuel on PTO, or leaking water into the cylinder to cause this to happen. Right?

  7. #7
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    42,569
    +1
    2,176
    Water ingress into the combustion chamber tends to ‘steam clean’ the piston top, leaving it with very little carbon.

  8. #8
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3
    K447, You have a ton of knowledge and experience. What was your first thought? Lean - not getting enough fuel supply?

  9. #9
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    42,569
    +1
    2,176
    Quote Originally Posted by ValleyRacer2 View Post
    ... What was your first thought?

    Lean - not getting enough fuel supply?
    Lean burn typically manifests as a crater/divot/hole in the middle of the piston, not erosion around the piston rim.

    Perhaps you have something weird going on with that particular carburetor that creates a detonation prone situation?

    Detonation damage can look like what you posted. What causes detonation?

    Fuel octane too low for the engine compression.

    Incorrect (too tight) squish clearance, due to piston too tall or cylinder/cylinder head modified/shortened.

    Incorrect cylinder ignition timing, ignition event occurring too early in the cycle. Incorrect/twisted crank phase, CDI or stator problem ...

    All that said, carburetors are not my thing. Others with more carb experience may have differing thoughts about your engine.

  10. #10
    ValleyRacer2's Avatar
    Join Date
    Apr 2020
    Location
    Apple Valley, Minnesota
    Posts
    62
    +1
    3
    Thought. I upgraded ignition when I rebuilt. During that time to get it to run, I had to swap the CDI blk/purple and blk/green. At that time you provided that as a solution. With the swap it fired right up. Is there anything to this that I should review?

Page 1 of 4 123 ... LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. thoughts on blown piston
    By jasonze in forum 4-Tec Performance
    Replies: 12
    Last Post: 05-26-2015, 02:52 PM
  2. Bad gas......curious answers...own thoughts?
    By LA Dawg in forum Northwest Rides
    Replies: 11
    Last Post: 05-12-2013, 09:12 PM
  3. haveing BAD THOUGHTS
    By twisted shaft in forum Sea Doo Open Discussion
    Replies: 10
    Last Post: 10-14-2011, 05:50 PM
  4. Replies: 0
    Last Post: 08-14-2011, 04:10 PM
  5. 1998 SLTX 1050 only firing off the PTO Cylinder
    By jons1050 in forum Polaris Open Discussion
    Replies: 6
    Last Post: 04-18-2011, 11:37 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
  •