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  1. #1

    Rebuilding XL800 Engine (Who can?)

    What do people typically buy just to freshen up a top end? Nikasil cylinders look great - I'm just not sure about the crank.

    180 hours on it - 50hrs that I've owned. Original OEM internals.

    Do folks oversize at this point when it's due for a top end? If so, what's done with the carburetor settings - this ski isn't the easiest thing in the world to tune.

    Thanks!

  2. #2
    Dave in DE's Avatar
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    With it still having nikasil cyl's. I'd just do appropiate sized pistons/rings with a light cyl hone. and spec out the rods on the crank to determine condition and maybe put new seals on crank. Then top it off with a fresh rebuild on the carbs. If you carefully record your carb High/low screws setting. Rebuild them and reset them back to the same set up your good to go. Then just have to adjust idle speed when in the water. The idle screw can easily be reached by hand.

    The nikasil is hard chrome over aluminum. they can't be bored oversized without replating them. If your going to do that it's best to send to US CHROME and have them replate to original size.
    Last edited by Dave in DE; 05-15-2019 at 08:35 AM.

  3. #3
    jeffg426690's Avatar
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    I would recommend starting with a compression test before doing anything. If compression is low, have your jugs mic'd by a shop (bike or ski shop) - you may just be due for new rings if anything. You need to know the condition and actual measurements of what you have before putting new pistons in so you can get the appropriate size - Yamaha OEM has four different sizes (a,b,c,&d) of OEM pistons to coincide with your actual cylinder measurements.
    A full carb rebuild is always a good idea and routine service along with full inspection of the entire fuel system from tank pickup all the way back to the tank.

  4. #4
    Sounds great, what PSI would be indicative of just rings? I have new oil injection lines and 2 genuine carb kits to install - I resolved a couple years ago a hot starting issue which was caused by a leaky seat. Now I'm just wanting to freshen up the top end.

    I am curious to see what the power valves look like. If I wanted to replace the power valves, what brand should I lean towards?

  5. #5
    Dave in DE's Avatar
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    General rule of thumb is below 100psi. The 800 when fresh is around 130/135.
    I would not do just rings though, always pistons/rings. no use in new ring on a piston that's sloppy in the bore with rings sloppy on piston. Yes as stated you need appropriate piston for the bore. That can be obtained from the number stamped on top of the cyl beside the power valve cover.
    Number code are as follows: 0-5 red, 6-10 orange, 11-15 green, 16-18 purple.
    Piston to cyl clearance is .0039"-.0041"
    The bore taper limit is .003"
    Out of round limit is .002"
    "All mesurements in inches."

    For power valves. I have an 01&02 GP800r both running the valves and linkage from sbt. The linkage is the permanent fix to the pin falling out.(an upgrade on the wave eater clips) both have been in service for several years with no issues.

    I thought from the sounds of your original post you already had cyl off sense you stated "cyl look great"
    Last edited by Dave in DE; 05-15-2019 at 07:10 PM.

  6. #6
    Hi. Used to have the same engine in a GP800r. As mentioned below 100 psi is due for a top end. After a rebuild it should be about 120 psi generally.
    General advice says every 100 hours for a top end really. Keep an eye on those power valves too. Thatís what wrecked mine.

  7. #7
    It's due for a top end. I am 106 and 100 on mine. I believe I will install OEM everything. I don't even see how the power valves were moving, it is gunked completely up.

    Should these just be installed back dry with a little 2 stroke oil?

    I have a wave eater clips btw - I purchased them when I bought the ski years ago after reading the horror stories.

    There was just no way I could get the bolts out of the manifold to install them.

    I have the whole engine out now.

  8. #8
    Dave in DE's Avatar
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    I've always lubed the valves and links with 2 stroke oil.


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