Thread: 1300r cylinder swap
10-02-2007, 05:11 PM #1
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?
10-02-2007, 05:19 PM #2
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.
10-02-2007, 05:25 PM #3
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.
10-02-2007, 05:36 PM #4
10-02-2007, 05:41 PM #5
10-02-2007, 05:51 PM #6
- Join Date
- Nov 2005
- Charleston, SC
I had a guy buy my 2 good 1300r (05) jugs and pistons so he could put them on an 800
10-02-2007, 05:56 PM #7
- Join Date
- Aug 2006
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.
10-02-2007, 07:36 PM #8
800 cyls are used mostly for triples when used in a 3cyl application. Different transfer and exhaust ports specs.
10-02-2007, 08:49 PM #9
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.
10-02-2007, 09:12 PM #10
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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