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Discussion Starter #1
Hi, I have a waveraider 1100 that blows a hole on the top part of piston number 3 to the exhaust side. This is the 2nd time it does it. When I install the brand new piston, it runs like a champ, no other jet ski on the lake can out run mine, but it only lasts for about an hour, then I just hear a popping sound and loose speed. When I took off this piston it had a layer of oil around, so it was not dry. I don't know what I am missing to fix to avoid this from happening again. One thing I noticed is the head gasket for cylinder 3 has a ruptured metal ring, could this be to blame for the piston blowing a hole? I am attaching some pictures of the whole thing, if anyone already went through this or can give me any ideas as to what to do, your help will be greatly appreciated.

THanks,

Hector
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I have a 760 of that year and just replaced both pistons due to lack of oil. I don't know but that hole was maybe caused by a piece of metal, perhaps from the head gasket, getting jammed between the piston and the head. You don't show a pic of the inside of the head, but look for some evidence there. Is the spark plug intact? Can you see anything in the bottom of the crank case, like what might have poked the hole? At a minimum you need to find the missing piece of piston.
 

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That looks like a lean run that cooked it. I'd look at the carbs. It would probably run great just to the point that it cooked the piston if it were running lean. Are you running pre-mix or still have the oil injector?
 

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Discussion Starter #4
I am running premix at 40:1 on 83 octane, but I was recently told that this ski should be running 93 octane at 32:1 mix. Also, I was going full throttle at over 65 mph when it popped, I was also told that it could be a leak on the crank seal? I also beleive that the carb is not adjusted right, it only has one turn out on both the high and low screw. I will adjust to 1.25 turns out on the low and 1.5 turns out on the high, or do you think I should go 2 on the high to run much richer?

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I am running premix at 40:1 on 83 octane, but I was recently told that this ski should be running 93 octane at 32:1 mix. Also, I was going full throttle at over 65 mph when it popped, I was also told that it could be a leak on the crank seal? I also beleive that the carb is not adjusted right, it only has one turn out on both the high and low screw. I will adjust to 1.25 turns out on the low and 1.5 turns out on the high, or do you think I should go 2 on the high to run much richer?

Thanks
What kind of carb are you runnin? You won't do any good with the low screw that is for take off the High jet will do the job.If it is a Mikuni you should be able to jet up the main jet. You were runnin lean at WOT, that is why it ran good but pop, increasing your octane will surely help. The higher the octane the cooler and slower the burn. look at your piston wash with a flex light after you run it hard. I'll bet you had aluminum stuck to plug as well. I use to run EGT gauges on my snowmobile. Aluminum melts at 1200 degrees, use to run mine at 1100 degrees.;)

BTY my Seadoo RXT RIVA Stage III runs 78 MPH thats one you won't beat, but I will stay off your lake lol
 

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Discussion Starter #6
Thats fast, you must be going with your feet up in the air at that speed, lol, i have 44 mm mikuni carbs, so ill just adjust the high screw .5 or maybe even one more turn out and see how it runs.


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Thats fast, you must be going with your feet up in the air at that speed, lol, i have 44 mm mikuni carbs, so ill just adjust the high screw .5 or maybe even one more turn out and see how it runs.


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One other thing to remember, with a two stroke try burping it after along wide open run by hitting the throttle a few times. This will dump raw fuel into the jugs to help cool it, when you let off the gas after wicking it the jugs are heat soaked and expand, so burp it a couple of times.:thumbsup:
 

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Discussion Starter #9
Yea its modified it has 82.5mm pistons, and everything that it has is made from riva racing. The carbs are 44mm mikunis.
 
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