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  1. #1

    GP1200 pressure test failing

    I had to change a stator and noticed some leakage into the front coil area. I did a pressure test and I am losing around 1 lb per minute. I sprayed some water on the front casing and I can see leakage bubbles between the casing halves on both sides. It is not the seal but rather the gasket between the two casing halves. The leakage is at the protruding rounding edge about 3/4 " from the seal itself. I tightened the blots underneath but it did not help.

    If I can clean the surfaces should I try applying gasket sealer material like "The right stuff" or even a little Marine Tex to see if I can seal the air leaks? I did not want to split the cases to repair this leak - don't feel like it is something I want to attempt.


  2. #2
    Old Ski Insanity w/rpm500's Avatar
    Join Date
    Aug 2005
    Crystal River Fl
    the split at the case is sealer gasket.. to do this right and not have a possible lean condition (seizure) you must split the bottom half , clean and reseal...check the o/e parts finder for a view of this

  3. #3
    If I flip the block can I remove the bottom case without removing the pistons or the piston jugs? If so can I also lift the crankshaft ends slightly to clean the case surfaces and replace the seals? Do I use 3m 1211 on the seals and case or the Right Stuff to create a gasket and lock the seals in.

    When I pulled the front flywheel I found a small leak at the seal bottom. So I found 4 leaks...seal bottom, sides next to the front seal and a small case leak on one side. Total leakage was just over 1lb per minute.

    I would rather not split the cases and pay someone but I do not know of a competent 2 stroke builder in my area.

    Thanks - I saw stuff written on the 100 so I was wondering if the same stuff would apply to the 1200 too.

  4. #4
    Old Ski Insanity w/rpm500's Avatar
    Join Date
    Aug 2005
    Crystal River Fl
    1211 +++( only stuff i'd use in that spot) , yes to just spliting the bottom,and being able to lift the crank slightly to clean surfaces'. but you must remove all the side covers ,stator rings ect that use both halfs for support or you'll bust something...
    the 1100 info applys for the 1200 for most procedures..
    I have never needed to 'nest' seals on a ski with a compound,but a seal set or 1211 should also work there..
    when assembling make sure all your pins (bearing locators ) and split rings fall into their various slots before tightening

  5. #5 are suggesting I probably don't really need to apply 1211 around the oil seal surfaces themselves..

    When I lift the cover there should not be any loose componenets are far as I can tell ..except maybe the dowel pins possibly. Correct?

    You mentioned split rings..what exactly are you referring to? I plan on splitting the case, cleaning inside and installing new seals and not disturbing any other parts if it is at all possible. Hone marks look good on the 2,3 cylinders but the first is barely visible if at all. Then again they had to repair the first cylinder twice due to seizing - oil issue, but that was years ago. Never noticed the condition of the cylinder back then after the repairs, even when I pulled the head a few years ago.

    Anything else I should be aware of? Thanks a lot. Starter bendix looks like new still.

  6. #6
    Have the cases split...(flywheel off, coupler off etc.) extremely clean inside--I expected to find oil, grease etc. like the front stator area but it looks like it is new inside ---a few little rust spots on the rod shafts

    Seal removal--I need to lift the crank slightly to slide the seals out of their seats - crank doesn't seem to want to lift out any - should I hit it slightly with a rubber mallet? Should I have the pistons at a certain position - like making sure none are bottomed out but slightly up from the bottom most position?

    Thanks for all your help.

  7. #7
    Old Ski Insanity w/rpm500's Avatar
    Join Date
    Aug 2005
    Crystal River Fl
    position wont matter as your lifting only a 1/4 inch or less ,besides nothing can push down further..... rubber mallot but only light taps as it will just jump apart.. the split rings are on the bearings (thou you may have the black 'double stripe' anti rotation strips built into yours).our older skis used the rings for locking location and to help seal the cylinders from each other.. you'll see them on the bearing o/d's or between the cylinders (they look like big steel washers sitting in a groove or thin aluminum plates between the cyliner webs)..Usage varies from type and year ,but you must make sure they are all seated properly before bolt up, along with the little roll pin locator that are also on the bearing O/D...(these nest in a small little chamfer cut on the splits top half centerline,or in locator holes drilled in the top half) locate any wrong and you WILL damage something...

    those seizures could also have happened from the pressure leaks you have found... good find !!

    just a note: I'm giving you this info with hopefully your understanding I dont own or have built a 1200.. just a sister motor, the 760 twin(it's basiclly 1 less cylinder) and having built multi year 500's...

    the 1200 owners arnt to forth comming lately, so i though my comments would help...

    read mp's raider or kris's gp build sticky to get much more on the tripple motors ...
    the YAMI shop manual is priceless for building these along with the excelent SELOC issue'd one...

  8. #8
    quadzilla's Avatar
    Join Date
    Apr 2007
    LOCH NESS Monster-Land

    Cool Hi


    So far you seem to be doing just fine with this case reseal..

    I would suggest you replace the crank seals with new OEM one's as a matter of course.. can supply you these for change out of $50.. (parts 7,8,9.)

    As suggested a couple of taps with a rubber mallet will pop the crank free..
    The locating pins on the crank bearings.. will be self explanatory when the crank pops loose.. (they all go into the top case half)
    I would recommend you rotate number two piston to top dead centre before you pop the crank up..
    That way there will be little chance of you lifting any of the pistons too far out the bottom..!!

    If you can, get a helping hand to assist you while you reseal the case halves,
    Get them to hold the crank up a little bit while you apply the 1211 round the seal recesses..
    ALSO helpful while you line up the locating pins..?

    This isn't a particularly difficult job.
    You just need to be methodical and accurate when you line up the pins..


  9. #9

    Smile Very nice thread

    This is a very informative thread.
    We need more like this with instructions that a shade-tree mechanic can follow.

  10. #10
    Thanks for all the HELP!

    I finally got the seals and gaskets from SBT. Decided to replace the gaskets instead of cleaning and reusing. SBT prices were pretty good. Seals are not the OEM Yamahas but look pretty close and seem to be good quality. I also bought a shim kit since I expect to have to do a realignment since I removed the motor support brackets. Shim kit was expensive!

    Anyway I got the cases back together - now I understand the pins that were referred to. Pistons still move so hopefully everything is seated properly. Went back together in a few hours. Used Hondabond HT since no one carried 3bond 1211.

    Pressure testing now but so far it is holding 8lbs without any leakage for more than 3 hours. Will leave overnight but it seems to be airtight now. All 3 leaks fixed.
    Cleaned the starter - plenty of brush left - this is true of all my skis - 97,97 and a 99. The starters always look great when I open them up. Not sure why there are so many for sale on Ebay.

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