Page 1 of 8 1 2 3 ... LastLast
Results 1 to 10 of 73
  1. #1
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Location
    Cleveland OH
    Posts
    17,328
    +1
    29

    Any guesses? Piston failure

    I was just starting my hi speed passes after break in when the engine shut off at WOT. The engine had been running for more than 15 mins, working my way up the RPMs. Started getting into the 6400 RPM range when she shut off. I noticed the gas tank was under vacuum and hoped it was that. WRONG!!!!!! This is the PTO cyl and Wiseco piston. I was still running 32:1 oil and the PTO carb was actually dribbling out the jet. There is actually a puddle of fuel in the bottom of the cases from it. So, lack of oil is not the cause. The CEN has a very light wear mark on it, and the MAG is fine, both are holding 135 PSI compression to this ones 95 PSI. It appears most of the damage occured on the 4 "corners" of the piston, not all the way around. Any guesses as to the cause of this damage?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	my ride 002.jpg 
Views:	192 
Size:	986.0 KB 
ID:	42184   Click image for larger version. 

Name:	my ride 003.jpg 
Views:	108 
Size:	969.3 KB 
ID:	42185   Click image for larger version. 

Name:	my ride 004.jpg 
Views:	92 
Size:	921.1 KB 
ID:	42186   Click image for larger version. 

Name:	my ride 005.jpg 
Views:	149 
Size:	993.6 KB 
ID:	42187   Click image for larger version. 

Name:	my ride 006.jpg 
Views:	96 
Size:	938.0 KB 
ID:	42188   Click image for larger version. 

Name:	my ride 007.jpg 
Views:	90 
Size:	912.1 KB 
ID:	42189  



  2. #2
    axgrider73's Avatar
    Join Date
    Feb 2007
    Location
    Southeast Ohio
    Posts
    2,059
    So, I am guessing lean from a pluged fuel tank vent.

    Maybe the vent is only blocked part way, allowing the release of fuel at lower rpm's but when you cracked it open it couldn't keep up.

    I am not real sure how long it would take the piston wash to adjust but I would think that it is possible that this happened so fast that the piston wash wouldn't have time to adjust and show a lean condition???

    I am in no way an expert, so that's just my thoughts.

  3. #3
    la90043's Avatar
    Join Date
    Oct 2006
    Location
    Los Angeles
    Posts
    1,201
    exhaust ports in cyclinders not rounded/shaven enough for rough edges?

    out of round cyclinders? bad bore?

  4. #4
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
    Join Date
    Jul 2007
    Location
    Cedar Rapids,Iowa
    Posts
    6,381
    +1
    23
    I hate this Bad Memory of mine,maybe it'll jog someone else's.There's a tech note from maybe team k.It refers to mainly 2 stroke bikes I think,But it shows the 4 corner sieze.Maybe a Cold Sieze..The water is cooler then normal now and your not running a thermostate. Hate to see it happen to you Kev.If that's the cause i'll have to watch it this weekend.

  5. #5
    Tony's Avatar
    Join Date
    May 2007
    Location
    North Carolina
    Posts
    1,760
    +1
    38
    This is a good article on piston seizures. http://polariswatercraft.com.au/pistonseizures.htm

  6. #6
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Location
    Campbell, Ca.
    Posts
    14,100
    +1
    105
    Be sure to read the entire article by groupK
    But I would still like to know your clearance set-up. I've seen that when I set my Wiseco's up too tight.


    Four corner seizure - This is by far the most common type of seizure found in personal watercraft engines. Both sides of the piston will show heavy scoring and seizure marks on each side of the wrist pin hole. The pattern of these four seizure points often appears to be a perfect square, hence the slang term "four corner". The scoring takes place in this pattern because those areas of the piston casting are the thickest. When the piston is seriously overheated, the thick areas will expand and distort the most. High output motorcycle engines usually experience this type of seizure pattern when a piston has been fitted with too little clearance. Most experienced , and well meaning, motorcycle mechanics would take one look and immediately say that insufficient piston clearance is the cause. However that diagnosis, on watercraft engines, would be wrong about 99% of the time.
    Four corner seizures in watercraft engines are almost always a result of the engine creating more heat than the cooling system can exchange away. That is not to say that most cooling systems are under built, but rather that it's easy to make a modification that creates too much internal heat for even the most beefed up cooling systems. Even though a constant feed of cool water is being moved through the cooling system, the cooling system must be capable of exchanging the engine heat away at a rate quicker than the engine is creating it.
    The engine factors that have the greatest seizure related effect on operating temperature or excessive compression ratio or ignition advance, high rpm, insufficient fuel octane level, insufficient cooling, or any combination of these. Properly adjusting these same factors will have the greatest effect on total power output. The job of the professional engine builder is to find the right combination, or "blend", of these factors that will result in strong overall power output at a pace that your cooling system can keep up with. There are many mechanics and engine builders who have mastered their own combination "blend" that can get you all the power your after without risking a seizure. A group of mismatched modifications is a first class ticket to "seizure-land". Any inexperienced individual who sets up your engine with over 200 psi of compression and advanced timing, is also guaranteeing your arrival. If your big mouthed motorcycle buddy down the street tells you that he can make any engine "roost"...you should think twice. You could be in for a very expensive lesson.

  7. #7
    axgrider73's Avatar
    Join Date
    Feb 2007
    Location
    Southeast Ohio
    Posts
    2,059
    Tony that was a great site. There is a page that shows 4 corner seizures:

    http://polariswatercraft.com.au/pist...osticguide.htm

  8. #8
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
    Join Date
    Jul 2007
    Location
    Cedar Rapids,Iowa
    Posts
    6,381
    +1
    23
    THAT'S IT! Thanks Tony
    http://polariswatercraft.com.au/pist...osticguide.htm

    FOUR-CORNER SEIZURE
    This piston has vertical seizure marks at four equally spaced points around the circumference. A four-corner seizure is caused when the piston expands faster than the cylinder and the clearance between the piston and cylinder is reduced. Another common problem of this type is a single point seizure on the center of the exhaust side of the piston. However this occurs only on cylinders with bridged exhaust ports. The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range.

    Edit Note: Damn,you guys are quick.
    Xlint is running in older water now,and also Pissers(like myself). This may be a big concern for the Cold Water guys to watch for as things cool. I'm thinking maybe some in-line adjustable valves for the pissers or how can we set up a thermstate for cooler months. Or Maybe a way to run the water thru the triple pipe and then to the heads?
    Attached Images Attached Images  
    Last edited by Keddano; 10-17-2007 at 11:16 PM. Reason: thought

  9. #9
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Location
    Campbell, Ca.
    Posts
    14,100
    +1
    105
    Looking at the cylinders, I see much more than 4 corners affected. What was your bore size for the pistons you used?
    What was your ring clearance?

  10. #10
    cheatin' piston popper addicted's Avatar
    Join Date
    Jul 2006
    Location
    north jersey
    Posts
    6,188
    +1
    176
    wiseco's need alot more clearance than cast pistons. Like .007" instead of .004". I'm sure you know that, but it's something to double check

Page 1 of 8 1 2 3 ... LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Any Guesses??
    By ph2ocraft in forum Polaris Open Discussion
    Replies: 14
    Last Post: 03-05-2008, 12:35 PM
  2. Cleaning case after piston failure? Best approach?
    By snowrunner in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 06-03-2007, 07:41 AM
  3. Any Guesses on Speed?
    By DaveF in forum Kawasaki PWC Performance (4-stroke)
    Replies: 11
    Last Post: 03-17-2007, 11:15 AM
  4. Piston Failure???
    By beerdart in forum Polaris Open Discussion
    Replies: 16
    Last Post: 03-13-2007, 08:04 AM
  5. 65U Group K cylinder/piston failure.
    By Flying Scotsman in forum Yamaha PWC Performance (2-stroke)
    Replies: 14
    Last Post: 10-05-2006, 01:19 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
  •