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  1. #1

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    destroyed another piston and cylinder!!!

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ID:	226509what am i doing wrong?! the ski is a stage 2, basically. A little more history:i have had to replace two cylinders/pistons already, due to broken powervalves. Does this look like damage due to me not fully dissasembling the motor, to clean out the pieces i couldn't find w/ a magnet?..... Two more variables on my mind: 1. the spark plug on the cylinder in question appeared a little lean, from the previous ride. ...2. corrosion built up on the connections of the wires from the magneto to the electric box; ...so much corrosion that the ski was acting up in many ways: turning over slowly, powervalves not functioning properly, and occassional complete power loss--a couple of times at high speed---ANY IDEAS?


  2. #2
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    Quote Originally Posted by gixxedraider View Post
    Click image for larger version. 

Name:	098.jpg 
Views:	146 
Size:	90.5 KB 
ID:	226509what am i doing wrong?! the ski is a stage 2, basically. A little more history:i have had to replace two cylinders/pistons already, due to broken powervalves. Does this look like damage due to me not fully dissasembling the motor, to clean out the pieces i couldn't find w/ a magnet?..... Two more variables on my mind: 1. the spark plug on the cylinder in question appeared a little lean, from the previous ride. ...2. corrosion built up on the connections of the wires from the magneto to the electric box; ...so much corrosion that the ski was acting up in many ways: turning over slowly, powervalves not functioning properly, and occassional complete power loss--a couple of times at high speed---ANY IDEAS?
    we are going to need a lot more pics, info, and history to help out here

  3. #3

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    the ski started easily yesturday, at home , out of the water. It did seem to be reving up slow, and it back fired a couple times...at first, on the water, the acceleration was only a little off and the rpms were hitting 6900ish instaed of 7100ish..........then; all electonics shut off leaving me dead in the water. After jiggling the coroded wires, it started but still wasnt rite..Shortly after, it idled fine; but wouldnt run over 4k.............took it home , found 0 compression on the center, so i pulled it apart........p.s. it ran great for about 25 hours on the top end rebuild

  4. #4

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    i should be a certified gpr mechanic by the time this thing is as faithfull as my raider1100.......or is it certifiable(crazy)Click image for larger version. 

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ID:	226529 it's hard too see but that is where the cylinder is ruined.....looks good compared to the piston

  5. #5
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    what was damage?
    what was replaced?
    replacement parts were new or used?
    pressure tested motor?
    inspected crank and flywheel?
    carbs overhauled?

    backfired out of water or in water?
    backfired from intake or exhaust?
    more pics of parts (head, other pistons wash)

  6. #6

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    previous failures: powervalve broke in such a way that it fell in to the motor between the piston and the exhaust port-seizing the motor at an idle-damaging the piston(replaced with a used piston, possibly the wrong size. When i was able to afford r&d powervalves(and waveaters); i pulled alll three cyliders off to clean... i knew to space the rings apart and away from the exhause; but i didnt know about the locator pins for the rings.........long story short; the ring on one cyclinder spun around , expanded in the xhaust port desroying anothe piston and cyliner. this time i bought a new piston and told about the diff. size gpr pistons.......i had all three cylinders honed by riva, then i installed new rings, properly. After about 10 hours i installed f/a's, [email protected] heads, and changed carb settings to oside specs. Recently i installed the hole shot mod: in the process i removed the battery box. To do so you have to unplug the temp sensor wire and one other..this other one corroded in the 2 weeks i left it aprt...i believe, causing powervalve problems, hard starting(like a dead battery;but not), and most recently causing the whole ski to shut off while riding(elctrxClick image for larger version. 

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ID:	226532Click image for larger version. 

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ID:	226533Click image for larger version. 

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ID:	226534Click image for larger version. 

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ID:	226535ical)

  7. #7

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    It backfired in and out of the water, out the exhaust-i think

  8. #8

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    never been pressure tested or had the crank checked

  9. #9
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    Quote Originally Posted by gixxedraider View Post
    never been pressure tested or had the crank checked
    first off if the motor was running then locked because of something jammed in the exhaust port, it may have twisted the crank... twisted crank will throw off ignition timing which can cause a backfire out of the exhaust
    - it would be nice to know which cylinder had the pv jamed in the exh port...

    also with the motor eating so many pistons I would highly recommend having the crank inspected for debris in bearings, which can cause pre-mature bearing failure, and they can check it for phase and weld it (Crankworks does a nice job)

    and last but not least, pressure test the motor to make sure you dont have an air leak which will take out pistons and/or crank bearings

    Lowell sells a nice pressure test kit, or you can rig up something like Oside Bill did a while back

  10. #10

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    thanks for the advise! i ordered a pressure test kit from lowell on tuesday. Crankworks quoted me $250 and a 2 week turn around. Sounds like 4-6 weeks withoiut riding; if the crank is ok. I'm probably gonna clean out this crank as best i can and put it back in the ski, with another cylinder---meanwhile i have another crank, with much less history, to send to crankworks. Do a full rebuild w that crank add some 1300 cylinders and ported crankcase(thank you "crg's list") I know it's stupid to run the origional crank; but it should get me through till the other motor is together......addicted!!!

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