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  1. #1

    Join Date
    Jun 2021

    Xlt1200 problems after rebuild

    Hello all, Iíve helped myself out of a jam numerous times from reading posts on here but this is my first time posting my own.

    Last February I got a 2003 XLT 1200 with about 130 hours on it. I tested compression in the guys yard with HF compression tester and all read around 90-100psi. He said he just replaced the starter and bendix too, and it ran pretty good as best as I could tell, so I bought it. First time out on the lake, driveshaft stripped because the engine wasnít aligned properly after he replaced the starter and bendix... fixed that and properly aligned engine and didnít have any more issues with that. Engine started to run rough first day out so I rebuild the carbs and that helped a little bit. But still would run on 2 cylinders after it was warmed up, so I took it to the local shop that works on older 2 strokes and he drilled the carb adjustment covers and adjusted the carbs. Took it out shortly after that and it ran like a dream, for about 15 minutes till I went to a cove and started riding aggressively and the engine died. Long story short, after a long swim back to shore, I left the plugs out and the engine ingested water. Tried to get the water out by removing spark plugs and running starter but that never worked so eventually after a couple days of the water being in there the engine seized up solid.

    fast forward to a month ago and I decided to get a new WSM crankshaft and 3 new pistons and a full gasket set and genuine Mikuni carb kits and rebuilt the engine myself. Using a post I found on this forum as a guide I rebuilt it and got it all out back together and went to hook up the battery and the starter solenoid was stuck closed (I assume from running the starter for so long initially trying to get the water out) so I rigged up a winch solenoid to try and take it out as it was Memorial Day but after a few attempts the relay stuck closed too but it worked long enough to get the engine started so I new i did something right when I rebuilt it. Later that week the new starter solenoid came in, I installed it and a little voice in my head told me to take the plugs out look at them before starting it, and I sure am glad I did, there was water in the rear 2 cylinders. So right after that we took the exhaust and carbs and reeds off and stuck a vacuum down in crankcase to suck out water and put it all back together and it ran great but would bog as soon as you turn on the water.

    so let it sit overnight and the next day we took the exhaust, carbs and reeds off again in addition to the cylinder head thinking that maybe the head gasket was installed incorrectly but everything looked good, so this time we paid special attention to make sure everything was torqued correctly thinking that maybe thatís how the engine was getting water in it. Put it all back together, no water in cylinder 2 this time but still water in cylinder 3. So the next day we took the whole top end off the engine and found that when I originally rebuilt it, I installed the cylinder 3 base gasket incorrectly and water was getting in there. So ordered new top end gasket set to replace all the gaskets that had been taken apart a few times and after getting it all assembled it ran great on the hose so decided to take it to local lake and try it out. Ran great for about 3 hours, no issues starting, no warning lights, nothing. So went to another lake the next day and rode it around from about 10 in the morning til 7 or 8 in the evening, again no issues of any kind.

    My buddy ordered a island racing hole shot kit for it so I put it on, install went well, no issues there. Then the next weekend I take it out again and it runs great for about an hour, even at wide open for 10/15 minutes at a time. Went into some smother water and decided to do some hole shot runs to test out the kit. I was driving and doing some passes, then me and my buddy chill in the lake for 20 minutes or so, then he gets on and does a couple passes, then does 5 or 6 pulls from a dead stop to maybe 20 mph back to back, and after 5th or 6th pass it wonít rev above 4K and sounds like it running on 2 cylinders. I decide Iíll drive it back to the nearest boat ramp, about 5 minutes ride with the speed we were able to go. At one point on the drive to the ramp the rpms shoot up and it takes off like normal for about 5 seconds, then it never went about 4K again. We thought maybe it had gotten too hot from those pulls, so let it sit for about 20 minutes to cool off, start it up and ride it around the ramp for a minute, still wonít go above 4K rpms. We decided since itís still getting oil because oil pump is still operational, we would ride it back to the ramp were my truck is p, about a 40 minutes ride with the speed we were going. Get it on the trailer and take the plugs out and the middle cylinder plug is smashed.

    I get it back home and today I took it apart and found the middle cylinder is melted... anyone know what would cause this. Iíll get a new piston and cylinder and out it back in and should solve the issue but what is the original cause of a melted piston so I can avoid it in the future.

    XLT 1200
    waveater clips
    primer kit
    oetiker clamps and Tygon oil lines with oil pump
    new tygon fuel line and filter
    carbs rebuild with genuine mikuni kits and needle and seats
    pump seal kit
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  2. #2
    jeffg426690's Avatar
    Join Date
    Jul 2015
    Sarasota, FL
    Welcome to the Hulk! Tough story...
    When buying a older two-stroke, unless buying from a friend you absolutely trust and know the detailed service/mechanical history, always plan on going through entire fuel system and carbs before doing anything. That's just part of buying a used two-stroke, assume the ski has sat for an extended time and it's been eons since carbs were gone through. When doing carbs on an unknown ski, replace jets and needle and seat as well - the n&s can be leaking and the jets may have fuel varnish build up that you can't see or really clean well.

    The motor not going over 4k sounds like your power valves weren't opening, the pv servo is the typical culprit there. You don't really know when the middle piston had it's meltdown so that could have been the issue as well. Future ref though, check pv servo if not getting rpm above 5k or so.

    MUCH more importantly, you did not leak test the motor after your rebuild. That would have told you that the base gaskets were backwards (you're not the first to do that, don't feel bad) before you ever tried to start it. Again, after fixing base gasket problem you didn't do a leak test. There's good odds that you have an air leak, especially after filling it w water post rebuild. A leak down test is the best insurance for a rebuild, even the best builders get air leaks sometimes. An air leak causes a lean condition and makes carb tuning practically impossible and is a quick recipe for piston failure.
    It also sounds as though you did not run any break-in period after your rebuild. 4-5 hrs at various throttle positions with no WOT.
    Expensive lessons to learn, feel your pain as that's not the easiest ski to wrench on (like getting the carbs out... as you know...). The xlt is a fun and versatile ski Keep us posted on your progress, hope some of this is helpful.

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