Author Topic: Overbore cylinder question from newb  (Read 1092 times)

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Offline jasonseasen

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Overbore cylinder question from newb
« on: August 07, 2009, 12:25:04 PM »
Hi,
I picked up a basket case that I have been assembling over the past months. I noticed today I have a set of 65mm pistons and Wiseco rings. However, I will need to bore out the cylinders to allow the pistons and rings to fit. I measured the bottom to the cylinders for their thickness, the inner diameter is 64.2mm and the outer is 68.8mm.
My question, if I bored these cylinders to 65mm, will that leave enough thickness in the cylinders to perform properly? Also, should I be measuring from the bottom of the cylinders or the top?
Thanks,
Jason

Offline Big Jay

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Re: Overbore cylinder question from newb
« Reply #1 on: August 07, 2009, 02:16:28 PM »
If it is a 750, you can safely bore them to 65 mm, but that is about it.

Jay

Offline MCRider

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Re: Overbore cylinder question from newb
« Reply #2 on: August 07, 2009, 02:51:29 PM »
65mm is the ubiquitous 836cc kit. Most popular overbore, hop up kit.


For fun
http://www.nightrider.com/biketech/calc_displacement.htm

Buy it from Big Jay. They can do the boring too.   ;)
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline jasonseasen

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Re: Overbore cylinder question from newb
« Reply #3 on: August 07, 2009, 10:33:56 PM »
Thanks!
Also, is there anything specific that needs to be done to the head, besides a correctly sized head gasket? The standard pistons fit nicely under the valves, just wondering if that area needs to be resized?

Offline MCRider

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Re: Overbore cylinder question from newb
« Reply #4 on: August 08, 2009, 05:41:19 AM »
Thanks!
Also, is there anything specific that needs to be done to the head, besides a correctly sized head gasket? The standard pistons fit nicely under the valves, just wondering if that area needs to be resized?
Nothing else "needs" to be done. There is plenty that can be done. But its a budget issue, not a technical one.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MRieck

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Re: Overbore cylinder question from newb
« Reply #5 on: August 08, 2009, 06:04:13 AM »
Thanks!
Also, is there anything specific that needs to be done to the head, besides a correctly sized head gasket? The standard pistons fit nicely under the valves, just wondering if that area needs to be resized?
Nothing else "needs" to be done. There is plenty that can be done. But its a budget issue, not a technical one.
  That's gospel MC ::) ;D ;D
Owner of the "Million Dollar CB"

Offline Bill/BentON Racing

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Re: Overbore cylinder question from newb
« Reply #6 on: August 08, 2009, 06:07:27 PM »
Speed co$t money,how fa$t you want to go?,Big Jay sure like 1000cc kit, cylinder and top case 1/2 on way week afer next,on vacation now,Pistons are impressive,whole kit top notch,I think Jeff said if I send Sam Green 2009 Tour T shirt I get 20% off? Cool Thanks,Bill
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