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  1. #1

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    GPR 800 motor rebuild advice

    Need some input on my 2002 GPR 800, with 120 hours. Front comp is 140, rear 90. Total rebuild or top end only ? Removed cylinder head, no damage to rear piston or cylinder wall. Did notice oil lines were leaking, not sure if this caused a issue.
    Was thinking top end with, block off plate and go to pre mix.


  2. #2
    TuningForkMarine's Avatar
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    change your piston rings to RIK rings, Make sure to run compression test at WOT, with 1 plug in place

  3. #3

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    Quote Originally Posted by [email protected] View Post
    Did notice oil lines were leaking, not sure if this caused a issue.
    Was thinking top end with, block off plate and go to pre mix.
    Assume the oil lines were the issue...... check crank bearings for any discoloration. Make sure they are nice and shiny as opposed to dull grey or black and that the crank turns freely with no grinding. Replace the bearings on the small end.

    Go with fresh pistons and rings, making sure that the pistons are matched properly to the cylinders, and double check the power valves for cracks or deformaties. You could probably get away with reusing the head gasket provided that the aluminum is not bent or creased and there are no signs of leakage between the jackets and cylinders. New base gaskets are standard.

    Going premix is wise. Leak down testing is always good.

  4. #4

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    Quote Originally Posted by salty View Post
    Quote Originally Posted by sloan_w[email protected] View Post
    Did notice oil lines were leaking, not sure if this caused a issue.
    Was thinking top end with, block off plate and go to pre mix.
    Assume the oil lines were the issue...... check crank bearings for any discoloration. Make sure they are nice and shiny as opposed to dull grey or black and that the crank turns freely with no grinding. Replace the bearings on the small end.

    Go with fresh pistons and rings, making sure that the pistons are matched properly to the cylinders, and double check the power valves for cracks or deformaties. You could probably get away with reusing the head gasket provided that the aluminum is not bent or creased and there are no signs of leakage between the jackets and cylinders. New base gaskets are standard.

    Going premix is wise. Leak down testing is always good.

    Hello, what normally happens to the lines for them to be an issue? Thanks

  5. #5

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    update, finally had a chance to tear down motor. cylinders look great small scuffs , cannot even feel with fingernail. pistons look good, no damage or scuffing. Was thinking of installing new rings and gaskets. Would it be ok to hone the cylinders to remove the scuffing ?
    Going to remove oil pump, install block off plate. And go to premix 40 to 1 ?

  6. #6
    Some say you can hone the plated cylinders some say not. I am told it takes a special hone since the coating is so hard. Measure the piston and the cylinders they go in to make sure your clearance is not excessive. If the scuffing is very minor you should be able to get away with new rings. Follow the advice of all posters above. Checking the crank now beats finding out later.

    For Jet Pilot's benefit, the 1200 and 800 up until 04 or 05 or so had oil lines that were close to being too short and over time they shrunk up and could fall off at the carb fitting. In addition, they were held on by wire ties that also fatigued over time with each heat cycle. Most folks replace the lines with new, longer ones and use oetiker metal clamps on all lines to be safe.

  7. #7

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    I second the oetiker clamps. Change the oil lines over to good, high quality tygon or another 1/8 line. You can get it in blue or yellow. (I prefer blue fuel lines and yellow oil lines, makes it easy to find them, especially if someone else is borrowing and riding) Give the lines plenty of length, cinch em down with the oetiker clamps, and ride it like you stole it!

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