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  1. #1
    Buck3yeRideR's Avatar
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    Buy used topend, OR bore + new pistons?

    So here's the problem, i have 2 650's both with bad compression readings on the MAG cylinder.

    Should I:
    1.) Bore out the worst cylinders, and put in 3 spanking new pistonsin one ski. And transfer a good cylinder/piston to the other ski. OR

    2.) Buy a used topend and replace only the MAG cylinder/pistons on each ski OR

    3.) #2, plus take the time to pull all other jugs/pistons and give them a good honing and new rings.

    4.) #1, plus take the time to pull all other jugs/pistons and give them a good honing and new rings.

    -What are some good budget friendly pistons and where can i get them? I've had good experiences with wiseco.
    -What and average boring job cost per cylinder? If it's too ridiculous never mind that.


  2. #2
    Buck3yeRideR's Avatar
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    well did some thinking and found out some more information. I though the ebay piston kits included all 3 pistons for $90, nope its only for 1 piston so getting new pistons is out for me.

    If i hone and put new rings on will this bring the compression back to 130psi? J/w how to get my cylinders with 120/115/110 back to 130.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Are you conducting the exact same test as when you read 130 psi?

    1. Are you using the same compression tester?

    2. are you testing it on a warm engine?

    3. Is the battery fully charged and strong?

    4. Is the throttle held WOT?

    5. Are the spark plugs removed?

    If so, then you need to see if the cyl walls have any type of damage. what the piston clearances are now. What's the ring gaps at. etc... before we can make any recommendations.

    if the clearances are too big, you'll need to go to an oversized piston to get the compression back up. Honing the cyls will remove some material increasing the clearances, often reducing the compression.

  4. #4
    20 feet Boy's Avatar
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    Is a 650 a 3 cylinder. I thought the 650 were 2 cylinder. Or maybe I don't known what the hell I am talking about.

  5. #5

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    Pistons and boring on your Polaris 650 triple

    I have 650 pistons kits in stock either just pistons for 70.00 each 10.00 shipping or a Compete top end rebuild kit with all 3 pistons, rings, pins, clips, top end bearings and all the top end gaskets for 245.00 and 10.00 shipping And I will fit and bore all 3 of your cylinders 45.00 each total 135.00 when you buy pistons or the kit from me and a flat 35.00 return shipping Grand total 415.00
    Thatís a good deal let me know
    PM ME

  6. #6
    Seems like the cylinder exchange kit from SBT would be the least expensive and the way to go.

  7. #7
    Banned User
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    If you are interested I have a complete 750 top end bored and rfeady to go with new pistons and gaskets. Just bolt it on and go. 300 bucks. Will make the ski quite a bit quicker

  8. #8
    20 feet Boy's Avatar
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    Quote Originally Posted by 20 feet Boy View Post
    Is a 650 a 3 cylinder. I thought the 650 were 2 cylinder. Or maybe I don't known what the hell I am talking about.
    I thought I dint known what the hell I was talking about. Sorry I will bitch slap my self later.

  9. #9
    Buck3yeRideR's Avatar
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    Quote Originally Posted by xlint89 View Post
    Are you conducting the exact same test as when you read 130 psi? yes, but max i've read out of both ski's has been 120, sorry must of confused some of my words up.

    1. Are you using the same compression tester? yes

    2. are you testing it on a warm engine? no, should i be?

    3. Is the battery fully charged and strong? yes

    4. Is the throttle held WOT? yes

    5. Are the spark plugs removed? no, only the 1 i'm doing the test on, i just read that all should be removed.

    If so, then you need to see if the cyl walls have any type of damage. what the piston clearances are now. What's the ring gaps at. etc... before we can make any recommendations.

    if the clearances are too big, you'll need to go to an oversized piston to get the compression back up. Honing the cyls will remove some material increasing the clearances, often reducing the compression.
    Quote Originally Posted by lovehavenfun View Post
    I have 650 pistons kits in stock either just pistons for 70.00 each 10.00 shipping or a Compete top end rebuild kit with all 3 pistons, rings, pins, clips, top end bearings and all the top end gaskets for 245.00 and 10.00 shipping And I will fit and bore all 3 of your cylinders 45.00 each total 135.00 when you buy pistons or the kit from me and a flat 35.00 return shipping Grand total 415.00
    That’s a good deal let me know
    PM ME
    thanks, but no thanks. No doubt you do quality work and service, however i'm trying to do things extremely cheap since i got both these ski's for free.

    Quote Originally Posted by BryanP View Post
    If you are interested I have a complete 750 top end bored and rfeady to go with new pistons and gaskets. Just bolt it on and go. 300 bucks. Will make the ski quite a bit quicker
    No thanks, yes i'm a cheapace with these ski's. I admit it! Counter offer of $150 shipped No pun intended

  10. #10
    Banned User
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    If you do it cheap and end up doing it twice, did you save anything? Doing a new top end for maybe 150 to 200 bucks more than doing it cheap will ensure it lasts years and will be reliable if well cared for. Just fix one and you might be fixing another one sooner than you would like to. Would you rather wrench or ride? Do what you want, but my suggestion is to do it once, and do it right. Ride more and wrench less. I was presentedv with pretty much the same option as you with my SL 900 rebuild. I went for the whole new top end and I don't regret it one bit even though it cost about 400 bucks more than I really wanted to spend. The end result was virtually a brand new motor with many many hours of life left. And the best part is knowing that and having a blast riding it.

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