Results 1 to 8 of 8
  1. #1

    Join Date
    Mar 2006
    Location
    Burlington,NC
    Posts
    193

    Engine surging at WOT


    OK, This is a gp800r ski with about 20 hrs on powervalve repair. Good compression, about 130 psi. Engine ate powervavles a couple of years ago, pistons and cylinders in good shape so tore engine down and cleaned entire crankcase and parts of any possible metal shavings, installed new powervalves with waveater clip system, new piston rings, and rebuilt carbs with oem kit. On reassembly we questioned the type of gasket maker they sent us to button up the bottom end but used it anyway (was some sort of red jelly like substance) We also forgot to order a new gasket to go in between the carbs and the crankcase mointing point so we used some of that red jelly like substance and the old gasket and reassembled. Engine always seems to run great the first time out for the season, then it seems to fall off after each fill up until it surges as if the powervalves are kicking in and out and then just seems to run about 800 rpms off were it should be.

    Here is my Theory

    I have questioned the gasket maker we used, it seemed to be of the type that really may not totally dry, makes me think that the crankcase may be loosing it's airtight integrity after the engine gets warm and experiences repeated pressure and suction cycles. After sitting for a long period (month or so) the gasket maker reseals itself and the engine runs good for a while. I talked with Tommy Jordan about this a little and he seems to think it is more than likely a carb issue instead of a gasket issue, however, the carbs were rebuilt and were pristine clean. Could a poorly sealed crankcase cause these problems or am I smoking something? Before I pull this engine again I could really use some help, suggestions, etc.
    Thanks all


  2. #2
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    A pressure test on the motor should have been done before install.I suggest this first off,then go from there.Its VERY important the engine holds pressure,if you have an air leak then all the time/money you just spent could be a waste.

  3. #3

    Join Date
    Mar 2006
    Location
    Burlington,NC
    Posts
    193
    Is there an easy way to do a pressure test now without pulling motor?

  4. #4
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    Sure,alot easier with the 2 cylinder motor.Check pm.

  5. #5
    spud's Avatar
    Join Date
    Jul 2006
    Location
    Oceanside, California
    Posts
    1,347
    +1
    2
    How is your servo motor? The powervalve gasket leaking is not going to cause a lean condition. The charge enters the crankcase when the piston comes up then is pushed through the ports when the piston comes down. The exhaust gas is being expelled when the piston comes down. Not much opportunity for atmosphere getting in there. Oily leakage around gasket is about all you will get. Now if you have a leak on any other engine components you will have problems. How long since the carbs were rebuilt? Is the fuel filter clean? New plugs properly gapped? Etc. Etc.

    Go ahead and seal the powervalve covers up good, but find the gremlin. Do you have a tach on it? Are the rpm's falling at wot? How do the plugs look?

    Try the old unhook the servo if rpm's aren't falling and it isn't going lean.

    My suspicion is carbs need attention.

  6. #6

    Join Date
    Mar 2006
    Location
    Burlington,NC
    Posts
    193
    Powervalve gaskets were not what I was concerned about, it was the crankcase. Not to sure about the gasket maker we used. Will try all the suggestions posted thus far, thanks to "spud" and "waterwoody" for suggestions.

  7. #7
    spud's Avatar
    Join Date
    Jul 2006
    Location
    Oceanside, California
    Posts
    1,347
    +1
    2
    Better pressure test it then and check out the carbs. I thought you did a powervalve rebuild.

  8. #8

    Join Date
    Mar 2006
    Location
    Burlington,NC
    Posts
    193
    The engine ate the powervalves in 2005, surprising that there was little damage to the cylinders and pistons, howevere there were tiny metal shavings in the exaust so in spring 2006 we pulled the motor, tore the whole thing down, cleaned and checked it out, then installed new rings, top end bearings, powervalves with waveater system, cleaned the carbs and rebuilt them, then buttoned her back up. Ran really good for a while, then RPM's started falling off. Talked about pulling over the winter but it was spring 2007 before we knew it so we decided to ride it and check it out. Rode good 1st ride or two last year then RPM's started falling of again. Same thing this year, decided to ride it before pulling it this year, ran good 1st ride with some surging, ran great second ride, ran like crap 3rd ride low rpm's and surging Go figure
    Last edited by Fandini; 06-29-2008 at 09:55 PM.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. 1999 polaris slth 700 95 hp engine surges at 35 mph and tops out
    By glwhitlo in forum Polaris Open Discussion
    Replies: 9
    Last Post: 06-03-2015, 10:28 PM
  2. 1997 gti surging at wot
    By 4pinwink in forum 2-Stroke Performance
    Replies: 2
    Last Post: 07-16-2012, 11:57 AM
  3. 96 XP surges at WOT
    By mcrowe in forum 2-Stroke Performance
    Replies: 10
    Last Post: 07-13-2011, 08:54 AM
  4. 98 XPL surging at WOT
    By race24x in forum 2-Stroke Performance
    Replies: 2
    Last Post: 08-11-2008, 06:39 PM
  5. Engine surging at idle, possible causes?
    By 01xdime in forum Kawasaki PWC Performance (4-stroke)
    Replies: 9
    Last Post: 07-05-2007, 10:42 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
  •