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Author Topic: CB650 head on CB500  (Read 1356 times)

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Offline peter400four

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CB650 head on CB500
« on: May 30, 2018, 12:20:45 AM »
A question for the sohc experts out there.
I have a CB500 historic road racer in Australia. It runs a bog standard motor at the moment and I'm looking at getting it a bit more competitive. To that end, a mate told me I should use a CB650 head because there's much more room for larger valves.
My question is this ("finally" I hear you scream) Will a CB650 head fit on a CB500 base?
Thanks in advance for your answers.
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Offline calj737

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Re: CB650 head on CB500
« Reply #1 on: May 30, 2018, 04:35:24 AM »
Here's a thread that brings up the topic in a related sort of fashion. I'd also encourage you to read through the linked thread for Paulages 715 hybrid for more details.
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline Bankerdanny

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Re: CB650 head on CB500
« Reply #2 on: May 30, 2018, 11:43:01 AM »
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"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline peter400four

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Re: CB650 head on CB500
« Reply #3 on: May 30, 2018, 04:13:33 PM »
Thank you Cal and Danny for your prompt replies to my cries for help.
Those bikes you build, Cal, are works of art and the preparation a real credit to you.
Thanks for that PDF Danny, I was actually just about able to understand everything in it. (Fortunately for my bike, it's not me that does the development/mechanical/body/paint work, but a father and son who run a small business in northern Tasmania called B-Spoke Designs. I just ride the bike, keep the fuel and battery (total-loss ignition) levels up and check the oil. I'd even include a photo of the bike if I could work out how to do so.
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Offline calj737

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Re: CB650 head on CB500
« Reply #4 on: May 30, 2018, 05:46:21 PM »
Quote from: peter400four on May 30, 2018, 04:13:33 PM
Those bikes you build, Cal, are works of art and the preparation a real credit to you.
Kind of you to say, and maybe one day I’ll finish up the 500 with it’s custom frame being templates  ::)
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline peter400four

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Re: CB650 head on CB500
« Reply #5 on: May 30, 2018, 06:51:51 PM »
Wow, here's that photo I didn't know how to post.
I did what I should have done in the first place and had a look through the FAQ thread. Including a photo is so easy even I can do it.
Here's my little baby, based on a Harris-framed very worked Cb400 built by English engineer John Blanchard in the latter half of the 1970s. It did 150mp/h with the tallest gearing and regularly beat the 350 TZ Yamahas that were starting to take over, even at a club level. My bike has a standard 500/4 motor and the aim is to get that from just over 40hp at the rear wheel to 60-65hp without breaking the bank. Here's hoping.
« Last Edit: May 30, 2018, 10:04:20 PM by peter400four »
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Offline calj737

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Re: CB650 head on CB500
« Reply #6 on: May 30, 2018, 06:53:42 PM »
Great looking ride. I’ve got some more reading for you. Please wear a bib to mop up the drool  ;D
http://forums.sohc4.net/index.php/topic,171869.0.html
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline peter400four

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Re: CB650 head on CB500
« Reply #7 on: May 31, 2018, 12:28:38 AM »
No need for a bib on that thread Cal. I read it the other day and a bib didn't cut it, I needed a bath towel!! Beeudiful.
Still, our bikes already share some of the same attributes like a lightened crank (no immediate hp gain, but easier to spin up when the good bits get added) 520 chain and sprockets for lower weight and 4 into 4 open megaphone exhausts, but not titanium. Have no problems running the bike at club meetings and didn't even get pinged 18 months ago when Tasmania hosted the Australian Historic Road Racing Championships (probably because I was so far behind, they felt sorry for me).
I dropped HondaFreak a line to ask about the DMS cam he has. I couldn't find any DMS information relating to motorcycles on the internet, only cars, so I'm interested to hear what he has to say.

« Last Edit: May 31, 2018, 12:32:20 AM by peter400four »
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Offline calj737

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Re: CB650 head on CB500
« Reply #8 on: May 31, 2018, 03:02:38 AM »
http://www.daviesmotorsport.com

One day, perhaps before I perish, I'll get my son's 500 motor installed into a running bike. I am very curious about the performance of it. It will not be 70HP certainly, but surely should be well into the 50s, dare I hope to claw at 60.

I used Wiseco 59s, Mike Rieck Stage 3 head with +1mm intakes, CR-26s and a Megacycle 126-20 cam. It feels fast even sitting on the bench. It should be a handful for my son on the street. Its hard to get him off his S1000R long enough to focus on directing the frame build  >:( Plus work, and girls, and riding and girls...
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline bryanj

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Re: CB650 head on CB500
« Reply #9 on: June 02, 2018, 05:16:16 AM »
There is/was a member in Australia who had a sidecar racer with modified 500 using a 650 crank(longer stroke) and cam sprocket(Hy-Vo camchain on 650) but not sure about head, I think the bolt spacing may differ as the 650 uses long bolts but the 500 studs and nuts
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Offline DaveBarbier

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Re: CB650 head on CB500
« Reply #10 on: June 02, 2018, 12:37:43 PM »
The stud/bolt spacing is the same, you can use a 550 base gasket on a 650.
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