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  1. #1

    99 XPL 951 top end rebuild

    I'm currently rebuilding a top end and have some questions.

    One piston has some light scuffs that you can barely feel so I'm planning on replacing that piston. The other piston is perfect. Besides the one piston, I'll be replacing both sets of rings. I've debated replacing both pistons with aftermarket or just replacing one with oem.

    The cylinders show no signs of damage from the scuffing. They are glazed smooth, but you can still see the oem crosshatch through the glaze. The motor has 70 hours on it. The bottom end is perfect.

    What grit hone would you use to break the glaze?
    Stone or flex-hone?
    Flex-hone's site recommends 240 for nicosil and 180 for a regular cylinder.
    What kind of steel does a carbed 951 use?

    Thanks, John

  2. #2
    kecheme's Avatar
    Join Date
    Jul 2011
    Phoenix Az
    If this was my build I would go up to the next piston size and send the cylinders out for boring. Your top end will last longer that way. But it sounds like you want to save some money. In that case find 1 oem piston or cheap aftermarket top end kit. Use a stone hone its easyer and it wont catch on the ports like a flex hone. Use a low speed drill and lightly hone the cylinders.

  3. #3
    1+ on the stone.
    Did you identify the root cause, fuel lines, oil lines? There is a reason it failed

  4. #4
    I'm not sure we can call it a failure. It was running fine. It's a 99 that hasn't been run since 02. In Spring 03 I tried restarting it. I had no water flow and it over heated. It's been in storage since then.

    I took it apart recently to get it running. It wound up being a clogged piss line and the engine's cooling system was air bound. Taking the top end apart looked easy enough. I wanted to see what was happening inside and found the scuffed piston.

    I should post photos. I'm not sure how bad it is. You can barely feel it.

    The fuel lines are gray, but all intact and clear. They will be changed during this build.

    I will be running premix during break in. So I'll know the oil system is working if the oil level drops.


  5. #5
    What grit stone would you use? I couldn't find any mention of it in the manual.

  6. #6
    kecheme's Avatar
    Join Date
    Jul 2011
    Phoenix Az
    Quote Originally Posted by JohnMstrks View Post
    What grit stone would you use? I couldn't find any mention of it in the manual.
    280 grit if you can find it. I use a Lisle hone.

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