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  1. #1

    Looking at ultra 250 with dead cylinder

    I'm considering buying an ultra 250 for cheap that has low compression on the 4th cylinder. I have rebuilt quite a few automotive, industrial, boat engines in the past and am considering rebuilding the motor if everything else is in order. The bad cylinder has 20 psi and the rest are at 120 psi, leakdown test has not been performed yet. If the failure is due to the rings/piston will this cylinder be usable? I don't have a lot of experience with Nikasil. I've used WSM rebuild kits on my Yamaha 1200 motors in a jetboat. Are the WSM pistons and rebuild kit okay to use on this motor? My biggest question is what is the likelihood I would be able to pull the motor deglaze the cylinders and put in a new top end on a ski with 120 hours?


    *edit ski is a 2007


  2. #2

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    Think there is a known issue with pistons, fitting 260 pistons is a common option I believe.

  3. #3
    Yeah it seems like kawi has had issues with pistons my buddy had a low hour 300 and it lost a hole as well, has anyone used the wsm platinum pistons for one of these skis before?

  4. #4
    steve45's Avatar
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    The real problem with the 250 is the jet pump. When the bearings fail, they push forward on the driveshaft and trash the crankshaft, rods, crankcase, etc.

    I wouldn't take one if it was given to me.

  5. #5
    Let me out of here......I need to go on Greenhulk!
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    Compression #s should be more like 210-220 psi. I guess the gauge could be off. I would pass, the 300/310 has better motor and blower. Well worth an extra couple thou.

  6. #6
    Everything i've read says around 120 is good compression, 220 seems way to high for a blown or even a gas motor in general. I'm well aware of the issues with the 250 and have ridden the 250,260,300, and 310 for a decent amount of hours. My main question is basically if anyone has any experience with having a piston failure and how the cylinders look afterwards (are they useable). My buddy bought each ski as they came out and I got to ride them a lot. He did have a piston failure on the 310 and the shop fixed it that week and I don't think they did anything to the cylinders or replaced them just basically redid that hole. Anyone have experience with the WSM pistons for these skis? Or a similar budget friendly piston kit. My plan is to potentially rebuild this ski over the winter test and tune a bit and put it up for sale when its warm and sell my other ski to get a 300.

  7. #7
    Myself's Avatar
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    Quote Originally Posted by HDAV View Post
    Think there is a known issue with pistons, fitting 260 pistons is a common option I believe.
    Scroll through my Facebook page for a 250x rebuild. You'll likely find a cracked piston with no other damage. Update to the 260x kit for a slight bump in compression at the same bore size. I've used WSM top end kits on everything from old stand ups to the 250x and a couple 255hp Seadoos. Plan on a new SC belt and the KP Performance jet pump update kit also. There is also a bit of room for improvement on the intake and exhaust port matchup too. Also pressure test the stock intercooler or just go ahead and upgrade.

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  9. #8
    I looked through your page (must be fun getting to tear all those machines apart btw) so you reused the cylinders on that engine without any machining/replating etc? I would upgrade the pump before the ski ever touches the water for sure. I'm torn now would be awesome to get one of these running (for awhile) on the cheap. I can get this ski for 700 from a shop where the customer basically walked off after hearing motor was shot. I think it may be worth it I could get my money back in a part out if I was patient if the motor is shot.

  10. #9
    Myself's Avatar
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    Yes, piston cracked all the way through the wrist pin bosses and never damaged the cylinder.
    You could always look inside with a bore scope before buying it.

  11. #10
    Let me out of here......I need to go on Greenhulk!
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    Quote Originally Posted by boatman1 View Post
    Everything i've read says around 120 is good compression, 220 seems way to high for a blown or even a gas motor in general. I'm well aware of the issues with the 250 and have ridden the 250,260,300, and 310 for a decent amount of hours. My main question is basically if anyone has any experience with having a piston failure and how the cylinders look afterwards (are they useable). My buddy bought each ski as they came out and I got to ride them a lot. He did have a piston failure on the 310 and the shop fixed it that week and I don't think they did anything to the cylinders or replaced them just basically redid that hole. Anyone have experience with the WSM pistons for these skis? Or a similar budget friendly piston kit. My plan is to potentially rebuild this ski over the winter test and tune a bit and put it up for sale when its warm and sell my other ski to get a 300.
    You are correct, the numbers I posted were for the NA motor. Sorry I was not thinking you #s are good. I am on the coast in salt water so i see the worst of the worst. I guess if its a fresh water machine thats been maintained it might be worth a few bucks. Did your friend experience any issues with the heads cracking or the the blower coating on the 250s he ran? How is the resale market for these skis?

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