Results 1 to 10 of 10
  1. #1
    NIXON'S BACK!! cincygpr's Avatar
    Join Date
    Jul 2007
    Location
    Birmingham, MI
    Posts
    545

    Need some help reading my cylinders

    I posted something on my little project thread, but I figured it would get more exposure over here.

    I finally got around to opening up the engine to see what was the matter, and this is what I found:

    Cylinder head:

    #1 Cylinder dome


    #2 Cylinder dome


    #3 Cylinder dome


    Looks like some detonation in cylinder #2. Looking into the cylinders themselves confirms this, plus the possibility of a mild seizure in cylinders 2 and 3:


    Cylinder head:

    #1 Cylinder/piston



    #2 Cylinder/piston



    #3 Cylinder/piston



    Cylinder 2 DEFINATELY ran lean at some point in time, and a compression test before I opened the engine indicated zero compression in that cylinder, with #3 a bit low, but not too bad.

    So, I think the story went like this: I put on a freeflow without rejetting, and so, got the dreaded lean spot due to the accelerator pumps, resulting in the piston getting fried and a mild seizure.

    Should I replace the #2 cylinder AND piston, or would I be able to get by with just a piston? I'm not sure how long the scuffed spot (seizure?) was there on #3, as it ran fine all summer.


  2. #2
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    Location
    United States
    Posts
    11,875
    +1
    30
    If you clean the aluminum galling on the walls of the cylinder, and there is no damage to the plating you can get by with just a piston. I have used acid to remove this when it is a light seize. Looks like you had something else in #2 besides deto, there is some damage on head and piston top from either broken ring or worse a bearing.

  3. #3
    SpeedJunky's Avatar
    Join Date
    Dec 2005
    Location
    Michigan
    Posts
    1,118
    +1
    35
    #2 sure looks like you had something foreign in there bouncing around. Did you check to see if you had a broken piston ring ?

  4. #4
    mrbtd's Avatar
    Join Date
    Jul 2005
    Location
    Lindenhurst, Illinois, United States
    Posts
    4,309
    +1
    2
    For what its worth....I would take it all the way down to the crank @ least for an inspection.

  5. #5
    NIXON'S BACK!! cincygpr's Avatar
    Join Date
    Jul 2007
    Location
    Birmingham, MI
    Posts
    545
    Thanks guys! I'm going to remove #2 and #3 jugs today and have a look at the bottom end.

    HallPass sent me one of his spare cylinders and pistons just in case I need it, otherwise, i'm going to pick up a pair of new pistons and rings, as well as a powervalve retainer and WaveEater clip (both disappeared mysteriously).

  6. #6
    mrbtd's Avatar
    Join Date
    Jul 2005
    Location
    Lindenhurst, Illinois, United States
    Posts
    4,309
    +1
    2
    I saw those HP cylinders - You should be able to use those pistons with no problems.

  7. #7
    2000 GPRXP 4tec shooter98xpl's Avatar
    Join Date
    Dec 2005
    Location
    Charleston SC
    Posts
    2,717
    +1
    3
    Can you rotate the motor by hand? if so, does the #2 piston move up and down? Reason I ask is because if you have 0 compression on #2, then that usually means a rod broke or something else happend to the crank. I have found on these gpr cranks that when they seize they get knocked out of whack and need to be inspected. For the peace of mind at least, but you'd be surprised at what can happen to these crank and how quickly they can get out of balance.
    Just some food for thought for you.
    SHOOTER

  8. #8
    Altezza01's Avatar
    Join Date
    Jun 2007
    Location
    Destin, FL
    Posts
    1,527
    +1
    13
    in piston number 2 in the pic where the piston is down in the cylinder...is there a milky substance on the piston? if there is ten that's water intrusion....but it looks like something like a bearing came out and was hitting. you need to check the cases to make sure that pin isn't in there or whatever it was that was hitting. and check all your bearings. this looks like flyboys piston when his bearing rod came out.

  9. #9
    NIXON'S BACK!! cincygpr's Avatar
    Join Date
    Jul 2007
    Location
    Birmingham, MI
    Posts
    545
    Quote Originally Posted by shooter98xpl View Post
    Can you rotate the motor by hand? if so, does the #2 piston move up and down? Reason I ask is because if you have 0 compression on #2, then that usually means a rod broke or something else happend to the crank. I have found on these gpr cranks that when they seize they get knocked out of whack and need to be inspected. For the peace of mind at least, but you'd be surprised at what can happen to these crank and how quickly they can get out of balance.
    Just some food for thought for you.
    SHOOTER
    Yup, the motor rotated quite freely by hand, except when the good (#1 and #3) cylinders went TDC, and I had to break the vacuum.

    Quote Originally Posted by Altezza01 View Post
    in piston number 2 in the pic where the piston is down in the cylinder...is there a milky substance on the piston? if there is ten that's water intrusion....but it looks like something like a bearing came out and was hitting. you need to check the cases to make sure that pin isn't in there or whatever it was that was hitting. and check all your bearings. this looks like flyboys piston when his bearing rod came out.
    No, I think the 'milky substance' was just light reflecting off of the cylinder wall. The cylinder itself was relatively dry, but had a LOT of pitting and foreign debris stuck to its surface.

    Removed all cylinders and the #2 and #3 pistons today. Wrist pins looked good on both, as did the needle bearings. Rods looked good as well.

    I'll have some more pics tomorrow, but the culprit of all of the aluminum debris looked to be caused by a ring catching against one of the smaller intake ports, which took a good groove out of the side of the piston, possibly due to a lean condition (maybe? SOMETHING got hot, at least). Both rings were stuck pretty well in position along that groove line.

    Thanks for all the help, guys!!!!!!

  10. #10
    Altezza01's Avatar
    Join Date
    Jun 2007
    Location
    Destin, FL
    Posts
    1,527
    +1
    13
    there is loose metal debri in your motor somewhere. This is what might of happened.... A needle bearing came out and was hitting the top of the piston and your head causing those dings. Then the bearing dropped down the side of the piston causing the rings to stick which then cause it to catch a lip on the port. Hopefully flyboy or pistonwash will chime in. I'm actually the one who found 3-4 needle bearings in flyboys ski and it was right in front of them. If you can't find and metal in the motor it may have exited the exhaust port and out your exhaust

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. ok Polaris pros I need some help with my 1993 sl750
    By Frozen in forum Polaris Open Discussion
    Replies: 8
    Last Post: 07-31-2010, 01:47 PM
  2. need some help with my mods
    By homebrew in forum 4-Tec Performance
    Replies: 14
    Last Post: 10-15-2009, 10:49 AM
  3. need some help wit my XP hood gauges
    By TMPLUMBER59 in forum 2-Stroke Performance
    Replies: 5
    Last Post: 09-04-2009, 12:08 PM
  4. Need some help with my 97 XP
    By midnight08 in forum 2-Stroke Performance
    Replies: 7
    Last Post: 05-27-2009, 07:51 PM
  5. I Need Some Help With My Shark !!!!!!
    By sleblanc in forum Polaris Open Discussion
    Replies: 9
    Last Post: 12-20-2006, 03:17 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
  •