Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 23
  1. #1

    Piston with 0 PSI Compression - Reason Unknown

    I'm not sure what happened! GP1200R ran perfect, so beautifully. I was cruising around 40, and all of a sudden lost power. Piston number 1 seized, or something happened with it. No way its a mid seizure, makes no sense because of jetting. The powervalve is still there and appears to be in good condition. I haven't taken off the cylinder yet, so I'll update. When I took off the seat and felt the head, it was hot, but not hot enough so I couldn't touch it for a few seconds. I've added pics of the piston too, wash looks a bit rich, but at least its not lean. When I saw something was wrong, I shut it off right away and didn't try to run it. But I need a new sleeve and piston for sure. Sleeve is scratched, piston is chipped right by the exhaust port.

    Wiseco 80mm
    premix
    Carb adjustments were listed in my previous post:
    Currently, my carb adjustments are:
    110 pilots and 120 mains
    1-1/4 out on the low
    1-1/2 on the high

    My theories:
    Overheat
    Ring spun
    Lean condition(?)
    Powervalve went in slightly too much

    Any help would be appreciated, I'm lost.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	photo 1.jpg 
Views:	115 
Size:	100.1 KB 
ID:	338060   Click image for larger version. 

Name:	photo 2.jpg 
Views:	125 
Size:	111.4 KB 
ID:	338061  


  2. #2
    powerstroke specialist mikegp's Avatar
    Join Date
    Mar 2011
    Posts
    2,529
    +1
    190
    it looks lean or overheat. try using prox pistons, Wiseco pistons in my opinion are a bit soft, I see you mention reject , but was it tune properly?

  3. #3
    steach's Avatar
    Join Date
    Dec 2005
    Location
    Rock Tavern, NY
    Posts
    3,174
    +1
    174
    It was nice of them to imprint an arrow on the piston, to show where the damage will occur.

    http://www.greenhulk.net/forums/show...=221663&page=2

  4. #4
    Quote Originally Posted by steach View Post
    It was nice of them to imprint an arrow on the piston, to show where the damage will occur.

    http://www.greenhulk.net/forums/show...=221663&page=2
    Tell me about it -_-

  5. #5
    Quote Originally Posted by mikegp View Post
    it looks lean or overheat. try using prox pistons, Wiseco pistons in my opinion are a bit soft, I see you mention reject , but was it tune properly?
    The only tuning done was the carb settings I said above, I've seen those settings work a lot. It looked way too rich to me, but that wouldn't cause the piston to detonate!

  6. #6
    Click image for larger version. 

Name:	photo 1.jpg 
Views:	90 
Size:	101.2 KB 
ID:	338088Click image for larger version. 

Name:	photo 2.jpg 
Views:	92 
Size:	93.5 KB 
ID:	338089


    Heres More pics of the piston.

  7. #7

    Join Date
    Aug 2006
    Location
    Indiana
    Posts
    1,274
    +1
    81
    Looks lean to me, noticed the burned section on the top of the piston above the exhaust port. Just because the jetting is right doesn't mean its not lean. Leaness can be restricted fuel supply, clogged internal fuel filter, front crank seal leaking, or an intake/reed/carb gasket leak. Were you running on reserve? There have been issues with reserve fuel pickup lines being restricted in the tank, and #1 carb is the last carb to get fuel on the line.

  8. +1 by:


  9. #8

    Join Date
    Aug 2006
    Location
    Indiana
    Posts
    1,274
    +1
    81
    Is it just me, or does that piston seem twisted in the bore, usually the arrow points straight and centered to the exhaust port and that one looks like it is pointing a bit to the right. Same thing with the numbers stamps on the top of the piston, they seem tilted too. May want to check that the rod is not bent.

  10. #9
    Quote Originally Posted by LT1GMC View Post
    Is it just me, or does that piston seem twisted in the bore, usually the arrow points straight and centered to the exhaust port and that one looks like it is pointing a bit to the right. Same thing with the numbers stamps on the top of the piston, they seem tilted too. May want to check that the rod is not bent.
    The crank is brand new - thats how it looked even when I installed it.

    How can I fix the lean condition? I'm sick of riding it for an hour and fixing it for 100. Not to mention this stuff isn't cheap.

  11. #10
    sjorge3442's Avatar
    Join Date
    Jul 2014
    Location
    Philly
    Posts
    263
    +1
    6
    Quote Originally Posted by pedyke1 View Post
    Quote Originally Posted by LT1GMC View Post
    Is it just me, or does that piston seem twisted in the bore, usually the arrow points straight and centered to the exhaust port and that one looks like it is pointing a bit to the right. Same thing with the numbers stamps on the top of the piston, they seem tilted too. May want to check that the rod is not bent.
    The crank is brand new - thats how it looked even when I installed it.

    How can I fix the lean condition? I'm sick of riding it for an hour and fixing it for 100. Not to mention this stuff isn't cheap.
    Fix the lean condition by finding what is causing it! Whether its a seal or fuel starvation from a clogged filter or a jet. 2 strokes need a fully sealed crank case to operate properly. Are you running premix?

Page 1 of 3 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. Yamaha GP1200R burning pistons with R&D head? Compression to high?
    By Quottro in forum Yamaha PWC Performance (2-stroke)
    Replies: 8
    Last Post: 11-06-2011, 06:17 PM
  2. 787 with 140 psi compression
    By dsgamermike in forum 2-Stroke Performance
    Replies: 3
    Last Post: 05-21-2011, 04:04 PM
  3. 1.00mm oversize piston with oem head ??
    By klze in forum Polaris How To & FAQs
    Replies: 5
    Last Post: 06-19-2008, 10:27 PM
  4. Help! GPR middle piston with hole. need advice.
    By jimshearer in forum Yamaha Open Discussion
    Replies: 16
    Last Post: 06-16-2008, 01:52 PM
  5. Mixing OEM sized pistons with oversized pistons
    By vanlohd in forum Polaris Open Discussion
    Replies: 10
    Last Post: 05-20-2007, 10:50 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
  •