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  1. #1

    Join Date
    Apr 2012
    Location
    Indian Trail, NC
    Posts
    92

    Question Mystery Solved...2000 SUV 1200 popping

    Took 2000 jetski out the first time since rebuilding the carbs. Used original Mikuni kits, 1.2 needle and seats, and correct jets per the manual and the same jets that came out of the ski. Put ski back together and the unit ran away the first time I cranked it. I pressure tested the engine and it would leak down from 6.6 to 3 psi in 10 minutes. I believe some was coming from the test plates. I reassembled the engine and used a new gasket on the intake manifold. Cranked up and ran on the hose but seemed a little rough. Finally, that cleared up and today we headed to the beach. Ski ran good the first 15 minutes, we headed back to the dock and checked the engine bay for leaking gas or anything to be out of place. Then we went out again and rode for about 5 minutes and I started hearing a pop coming from the exhaust. Few seconds between at first, then faster and faster popping.

    Now I have two non-running suv's.

    Any suggestion would be great.

    Thanks again,

    mdavidthomas
    Last edited by mdavidthomas; 08-09-2015 at 10:57 PM.


  2. #2

    Join Date
    Jul 2010
    Location
    KC
    Posts
    478
    +1
    1
    your rebuild did not pass the leak down test. you have to be very sure where the leak is from. leaking engine will let in too much air and cause lean condition that will burn out the piston.

  3. #3

    Join Date
    Apr 2012
    Location
    Indian Trail, NC
    Posts
    92
    Here is pics of new sparkplugs that were run today. This was not a throttle chop test.

    Cylinder #1

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    Cylinder #2

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    Cylinder #3
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    Looks like #2 and #3 are running lean. #1 didn't look to bad to me? Any comments.

    Thanks,

    mdavidthomas

  4. #4

    Join Date
    Apr 2012
    Location
    Indian Trail, NC
    Posts
    92

    Thumbs down

    New info....jetski ran great today for ~15-20 mins again and then started popping and missing. I checked compression on the jetski cold this morning and it was 120psi on all three cylinders. I am thinking maybe plug wires, coil or CDI. I jerked the plug wires off the spark plugs the day it ran away which pulled the boot off the number one cylinder. I threaded it back on and it seemed tight.

    Thanks for for any suggestions,

    mdavidthomas

  5. #5

    Join Date
    Jun 2011
    Location
    hopewell,Va.
    Posts
    141
    you need to sweeten up #2 and #3 carb alittle. did you check and adjust pop off on the carbs before installing them. you also need to find that leak or it will toast the motor. you can use soapy water test after you pump air into the motor. most times its the rear pto seal that leaks.

  6. #6

    Join Date
    Apr 2012
    Location
    Indian Trail, NC
    Posts
    92
    This was the same plugs after a 20 min run today. I adjusted idle and reset the low speed screws to 1 turn out. They looked a little wet but that was probably because I had to idle onto trailer.

    Cylinder #1
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    Cylinder #2
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    Cylinder #3
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    I plan to pull the engine and do another pressure check next week and soak all the gasketed seams. BTW, I did check the popoff pressure on the carbs. I used the original springs because the ones in the Mikuni kit either had a real high or real low popoff. Each one was at 58 psi.

    Thanks,

    mdavidthomas
    Last edited by mdavidthomas; 08-08-2015 at 09:07 PM.

  7. #7

    Join Date
    Apr 2012
    Location
    Indian Trail, NC
    Posts
    92

    Thumbs up Mystery Solved .... popping turned out to by Cylinder #1 plug wire

    Turned out to be the spark plug wire that was the culprit. When I jerked the plug wires off during the engine run away, the number 1 cap pulled off. When I screwed the plug cap back onto the stock wires, I did not see any stranded core wires in the plug wire; however, I was not familiar with the Yamaha spark plug wires. Today, I removed cylinder #2 plug cap to see how the plug wires were constructed and the stranded wires broke out of the core on cylinder #2 and fell out in my hand. So, I cut the stock wires back about 1 inch until I saw a good set of stranded core wires on Cylinder #1 and #2 wires and then I threaded the plug caps back on. Ran the ski for 2.5 hours with no popping. Apparently. as the wires/engine heated up, the connection started failing causing the cylinder to miss.

    Thanks for all the suggestions,

    mdavidthomas
    Last edited by mdavidthomas; 08-09-2015 at 10:55 PM.

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