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Discussion Starter #1
ok, last summer i picked up another 98 xl1200 not running but in decent shape hull wise etc. I fully expected to remove and rebuild the 1200 non pv engine at the time. Anyhow, replaced the starter, starter relay, battery and oil lines. She fired up but unfortunately mag cylinder showed 120psi, middle 118psi and rear 90 psi cold compression. [no aluminum on the plug] i ran it a couple of times last summer, once early this summer but needed to replace the steering cable so did that then took it out yesterday along with my teenagers on my other 98xl and raider 1100. I noticed a little less power but it ran ok. Once i parked it for a while then started it back up it didnt want to take throttle for a while but then picked up. I figured the pto cylinder was wearing more. Anyhow at end of day, it wouldnt start at the dock. I winched her on and brought her home. Compression check now show 60psi in PTO cylinder so out with the engine--i already ordered new top end 84.5mm piston kit and will have jugs bored etc. Will rebuild carbs with mikuni kits and put new front and rear crank seals in and clean and reseal the case after checking and cleaning the crank. will have a chance to pressure test when done as well.
The punishment comes from the undersized hull opening on the '98---kind of like building a ship in a bottle routine..wish me luck.
 

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If the cyl/Piston are scored as I am sure they are be sure to clean and check crank and rod brgs well.

Post some pics when you get it apart. To help confirm cause of failure. That cyl may have been going south due to an air leak at the seals. Or carb issues. That will need to be resolved.
 

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Discussion Starter #3
Thanks Dave, Yes i suspect some pretty good scoring. When i bought the ski a year ago, two of the three oil lines were off---that is the main reason i figured it would be an immediate rebuild so it surprised me that two of the three cylinders had good compression and the third one was marginal. I expect that it was run a bit with no oil or since it is the pto cylinder, perhaps the rear seal has been/is leaking and causing a lean condition. It also could be the carbs as who knows when/if they were ever cleaned/rebuilt and it did have some old petrol in the tank when i got it. I'll post up some info whenever I tear it down.
 

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Ok, the oil line being off is what sent it south. Once started no amount of oil will save it. Lol. I'll be around if you need help.
 

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Discussion Starter #5
Thanks, Dave. That is my assumption as well. I will know more once i get a look at the piston and jug. I plan to split the cases and install new seals anyhow just in case rear seal is hard and leaking. Will also rebuild all 3 carbs with mikuni kits. this particular hull is such a PITA i dont want to go back in any time
 

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Discussion Starter #6
ok, engine is out of hull. I removed the cylinder jugs. PTO piston broke the upper ring. a piece of it is embedded in the piston crown; small chunk of piston missing. Not much scoring on piston or cylinder. Will deliver to machine shop to bore .5MM. Unfortunately, three of the exhaust manifold studs snapped off and the manifold is stuck fast to the cylinders. [must have seen some salt water use at some time]. Anyhow any suggestions on how to pull that manifold off? I may just see if the shop can take care of it
 

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Keep those broken bolts soaking wet with pb blaster for several days then try removing the exhaust manifold. There is a bunch of corrosion around the bolt shanks. Once the manifold is off heat and pb blaster can be used to remove what's left of bolts. At least they broke high enough to get a pair of vise grips on.
 

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Discussion Starter #12
thanks. did that for several days with liquid wrench. used torch heat etc and even fashioned a home made puller out of channel iron. It took so much force it bent the steel. Finally ended up cutting the manifold flanges and then had to use a drift to force the manifold off of the studs. The studs really had become one with the manifold. Used stilsons and removed the studs from the jugs cleanly. I have to order a replacement manifold but otherwise done getting it apart. the jugs are off to the machine shop for boring
 

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Discussion Starter #13
oh i forgot to mention that my salt water use theory was proved when i dumped beach sand out of the jugs waterjackets. I guess it could have been freshwater sand but really looked like the course stuff we find on the sounds and backwater salt waterways of coastal NC
 

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Discussion Starter #14
While disassembling things I also found where one of the seams is beginning to split on the exhaust hose that goes from the engine outlet through the bulkhead into the rear compartment. It is Yamaha part 64T-14752-00-00. If anyone reading has a second hand one they want to sell hit me up. New is like $200.
 

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Discussion Starter #16
ok, engine is overhauled and back in the ski. Started it up on the hose last night..so far so good. I will hit the lake later in the week for break in. A couple of facts from the rebuild. used .5mm overbore Wiseco pistons. New yamaha front and rear seals. cleaned crank and lubricated with 2 stroke oil...bearings all smooth. cleaned crankcase and reassembled. pressure tested. engine held 8psi for about 30 minutes; good enough for me. Rebuilt the carbs with genuine Mikuni kits--wow did they need it. lots of white crap in the pumps and deteriorating o-rings etc. I would say ethynol fuel was left in it at some time
 
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