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Author Topic: 1968 cb450k1 engine rebuild question  (Read 201 times)

Offline Grayson

  • Posts: 10
1968 cb450k1 engine rebuild question
« on: May 26, 2018, 12:16:34 »
Ive built a few bikes but never done a full engine rebuild on a bike. I pulled the jugs off my 1968 cb450k1 the otherday and started messuring the cylinders to see of they were within the servicable limit or if i was gonna have to get them bored over (standard - 2.7560) (limit - 2.7600) but i took a ton of measurements and im getting an average of 2.9017 anyone have any suggestions? Can i bore it bigger? Was it bored to 2.9000 and now i just need to find some new pistons to fit this or maybe just new rings if i clean up the existing pistons. Thanks  for your help in advance.

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Offline TheCoffeeGuy

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Re: 1968 cb450k1 engine rebuild question
« Reply #1 on: May 26, 2018, 12:27:18 »
My experience with the 459 is that there are very few OE standard size pistons available.  The Service manual should tell you how big the 1 over 2 over 3 over and 4 over sizes are.  Typically you get pistons, then have the bore done to match. I suspect there is still room for another bore if needed.
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1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike
1982 Honda CB650 Chopper light

Offline Grayson

  • Posts: 10
Re: 1968 cb450k1 engine rebuild question
« Reply #2 on: May 26, 2018, 14:37:55 »
My experience with the 459 is that there are very few OE standard size pistons available.  The Service manual should tell you how big the 1 over 2 over 3 over and 4 over sizes are.  Typically you get pistons, then have the bore done to match. I suspect there is still room for another bore if needed.
Awesome thanks for the info
edit: it looks like i can overbore to 74mm just wondering if anyone has done this and if there is any issues that is could cause down the lane? im not trying to build a race engine or anything. most of my engine parts ill be replacing with ome parts, I just wanna bring some new life into this old bike and do it properly.

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« Last Edit: May 26, 2018, 14:53:49 by Grayson »

Offline teazer

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Re: 1968 cb450k1 engine rebuild question
« Reply #3 on: May 26, 2018, 15:13:56 »
THR racing will sell you a pair of 74mm pistons that are suited to 93 octane street gas.