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  1. #1

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    Help with compression loss!

    Hey Gang,

    I was hoping I could get some advice after I made some mods to my '02 GPR and now she won't run .

    I took a low hour ski this winter, and I added: reed stuffers, wave-eater clips/couplers, D-Plate, oil pump block off, Island racing tuned carbs, K&N flame arrestors, Jetworks mod, and high compression Speedworks heads (~160 PSI) with girdle kit. No CDI changes or porting, timing, pistons, etc.

    After all of my work this winter, I torqued everything to spec and fogged the cylinders for storage.

    When I DID try to start it (out of water just to see if she'd turn), here's what happened: I turned it for a couple of seconds with no response. Waited a couple of seconds, and repeated with same response. Repeated a third, maybe fourth time when it sounded like a 12G shotgun going off! Some smoke ensued from the tail pipe and from under the battery box.

    I checked compression to see what went down and here are the rough numbers (no throttle on test): #[email protected], #[email protected], #[email protected]. I then pulled the heads to evaluate. All three pistons looked fine with no obvious damage, the crank moves easily with gentle pressure on the pistons, and all three domes still look like no detonation ever took place (#1 has slight oil/fuel appearance, #2 has spattering of primarily oil appearance, and #3 looks like heavy oil appearance.) All gaskets appeared to be in place without cracks or leaks. Cylinder appear normal with no cracks.

    Where to now? Do I pull the cylinders, inspect, and then re-torque?
    I really don't know what went wrong!

    Any thought on running a high-compression ski or jetworks mod out of water with flush hose? special starting techniques with high-comp ski? Should I just go back to stock heads for reliability?

    Any thought are welcome; thanks !!


  2. #2
    krispaintballz's Avatar
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    Recheck compression with all plugs out and wide open throttle. Are you using a fairly good compression tester?

  3. #3
    My Jet Ski drinks more than yours Glenozzy's Avatar
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    I would take a hard look at the head gasket

  4. #4
    Ya Boy Trevor bajaeater's Avatar
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    I just blew my head gasket and it only dropped 15 lbs. Thats a big drop on this one. was ur rpms good on all three compression test? voltage up to get good crank to get compression up?

  5. #5

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    The top end is now off, so I'm afraid compression rechecking isn't going to happen anytime soon...

    When I did the check, I was very hesitant about potentially causing more damage, so I went no throttle, two plugs in/one out (compression guage), 4-5 cycle start. The compression kit is a Sear Craftsman (Don't laugh, but it's not from Harbor Freight either!)

    I just can't figure out what the "shotgun blast" sound was from.

    I may sound ignorant, but there should be three separate head gaskets on each dome--again, all looked good.

    When the engine was turning, I never got the feel that it was "about" to start.

    Should I re-torque the cylinder bolts, and just rebuild? After that sound, I just feel like something is way off...

  6. #6
    krispaintballz's Avatar
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    Quote Originally Posted by Bknblk View Post
    The top end is now off, so I'm afraid compression rechecking isn't going to happen anytime soon...

    When I did the check, I was very hesitant about potentially causing more damage, so I went no throttle, two plugs in/one out (compression guage), 4-5 cycle start. The compression kit is a Sear Craftsman (Don't laugh, but it's not from Harbor Freight either!)

    I just can't figure out what the "shotgun blast" sound was from.

    I may sound ignorant, but there should be three separate head gaskets on each dome--again, all looked good.

    When the engine was turning, I never got the feel that it was "about" to start.

    Should I re-torque the cylinder bolts, and just rebuild? After that sound, I just feel like something is way off...
    I would just check the cylinders and the walls, put it back together and retest. While you have the head off turn the engine over by hand and see if you see anything.

    Why did you take the whole top end off? Or do you mean just the head?

  7. #7

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    I removed the one piece head with three domes (cylinders/pistons left in place). Speedwerx head looks different from Rivas since Riva's are three separate domes and heads.

  8. #8
    Moderator OsideBill's Avatar
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    check your reeds also.

  9. #9
    Moderator OsideBill's Avatar
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    also do you have a primer?

  10. #10
    One day at a time..... N8R's Avatar
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    Quote Originally Posted by OsideBill View Post
    check your reeds also.
    x2

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