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  1. #1
    born riding's Avatar
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    1300r cylinder swap

    hey i heard a rumor that when yamaha made the gpr they made the cylinders for the 800 then for the 1200. i heard that they put 3 cylinders or pistons (800 type) on a 1200r and it made too much power. so they changed them. has anyone heard this and has anyone tried swapping the to see if power would increase? would this work with the 1300r?


  2. #2
    My son (mohawk man) jeffsntx's Avatar
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    Think about it...........

    800= 2 cylinders at 400cc per cylinder
    1200= 3 cylinders at 400cc per cylinder

    A 800 is a 1200 with 1 less cylinder. Same displacement per cylinder.

  3. #3
    enforcer's Avatar
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    I'm curious about this as well. The 800 made 120 h.p. on 2 pistons and the 1200 made 155 h.p. on 3 pistons.

  4. #4
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by enforcer View Post
    I'm curious about this as well. The 800 made 120 h.p. on 2 pistons and the 1200 made 155 h.p. on 3 pistons.
    Someone with a LOT more knowledge will have to explain it better than me, but you cant figure the HP per cylinder and apply that towards a figure. There is a lot of other things that come into play.

  5. #5
    enforcer's Avatar
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    Quote Originally Posted by jeffsntx View Post
    Someone with a LOT more knowledge will have to explain it better than me, but you cant figure the HP per cylinder and apply that towards a figure. There is a lot of other things that come into play.
    true dat true dat.I wonder if the ports or anything else is different and I had also heard through the grapevine that some people do use 800 cylinders and pistons but I dunno.I agree some else will have to chime in to add to this topic for shure.

  6. #6

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    I had a guy buy my 2 good 1300r (05) jugs and pistons so he could put them on an 800
    Mike

  7. #7

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    The 800 cylinders are ported much more aggressively than the 1200/1300, so much so that Group K doesn't want to use them for the pump gas 1390, something about the exhaust port height.

  8. #8
    Happily Self-Employed WFO's Avatar
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    800 cyls are used mostly for triples when used in a 3cyl application. Different transfer and exhaust ports specs.

  9. #9
    Me Hahn and Joe H204YOU's Avatar
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    The bottoms of the transfer ports closest to the exhaust port angle in under the exhaust port so they are undesirable as cores for boring,this is why group K wont use them.They are also about 1 mm or so taller on the exhaust port.In stock form they can be used on a three cyl single pipe and will produce a slight increase in HP and torque.

  10. #10
    philip_gpr's Avatar
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    the primary reason the 800 motor makes HP per cylinder is the single exhaust pipe works more effectively on a 2 cylinder motor than on a 3 cylinder motor

    I suspect because of the more effective exhaust pipe on the 800 they can then use different port specs - I have heard the 800 cylinders don't work that well on a single pipe 1200 (though they do work well on a triple pipe 1200)

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