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  1. #1

    What would cause sudden drop of pressure in one cylinder on a new motor?

    Seeing how the weather is starting to show signs of breaking I am trying to get my "project" skis actually fixed and fulfill my promise to my wife that they would be out of the garage in the Spring. One tactic I have used this Winter is that if you are constantly moving the skis around she will never notice that you added another one or two to the mix lol.....
    anyways I have a 2000 Sea doo RX that was garage kept and in great shape. Problem is that the previous owner had a dealer installed new engine replaced and it was only ridden about 4 or 5 times before it started running like total crap. so he sold it to me and now I am getting ready to dive in. It will fire right up but runs really rough. checked the compression on the cylinders and it was running around 135 for one and 45 for the other.
    First question is what would cause a new motor to drop off that much one on cylinder? Could it be as simple as a ring issue or do you guys feel it may be something deeper. thanks for the help guys!

  2. #2
    Derek45's Avatar
    Join Date
    Feb 2014
    MO. Mark Twain, LOTO
    I would verify the dealer installed a new rebuilt motor for starters, or what they did to the ski, It could be a wide range of issues, if it is a new motor, not broken in right, oil line poped off, oil pump falure, or a bad motor, But my biggest guess would say the carbs where not rebuilt and grey fuel lines replaced leaned out that cylinder but if a rebuilt motor from SBT then it should had been under warranty and should had been replaced unless Carb issue.

  3. #3
    wkuadam07's Avatar
    Join Date
    Feb 2013
    Bowling Green, KY
    DJMky, you aren't from here in KY are ya? Another Denny Marine job possibly? I have see 3 different skis come from there that the dealer told the owner that the put a new engine in... all 3 skis had very poorly rebuilt original motors. All had major problems, lack of compression on one cylinder, etc... All of the owners got lied to by these idiots... 2 of them were 787 RFI motors, and they both blew up again because of cylinder base gasket leaks. It also didn't help that the throttle position wasn't reset. When you do major work on a DI or an RFI you MUST reset the throttle position sensor in the computer. It has to be done using candoo or buds. Is it a DI?

    More than likely you will need to rebuild the motor again, at least the top end. "Simple ring problems" are fairy dust... They almost never exist. I'm not trying to be a dream killer... Pull the exhaust, and raves, you can then see the sides of the pistons, that will tell you what you need to know. If there is damage it should be obvious where it came from, could be that the new motor was bored and they forgot to trim the raves and the piston is damaged, could be a million things... Pull her apart and have fun. Once you have her fixed up and bullet proof that RX is a lot of fun.

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