1961 CB72 Project

G-Man · Post by **G-Man** » Mon Jun 23, 2014 12:49 am

Hi everyone

A little while ago I bought a rather sorry-looking 1961 CB72. It was registered in the UK on 1st January 1962 and both engine and frame number are the same. I have the original registration documents which carry a list of all the owners from new.

Work on the bike proceeds when I have time but I will try and make a thread here to let you know what is happening with the bike.

Here is the bike as collected. One of the previous owners has swapped the wheels and front forks for later items. The original fenders have gone and the mufflers pre-date Vince Lupo's project by 40 years or so.

CB72-Right Side.jpg by graham.curtis, on Flickr

Stripping commences. Notice the extra breather pipes from the top of the head to the rear licence-plate bracket.

Someone had fun in the '60s making this into a cafe racer. both numbers end with '969 so this bike should have an SLS front brake. Rear brake stay is aluminium.

CB72 Left Side.jpg by graham.curtis, on Flickr

G

G-Man · Post by **G-Man** » Mon Jun 23, 2014 12:58 am

Some details from the bike.

Brass 'model plate' on the swingarm showing bike details.

Model plate.jpg by graham.curtis, on Flickr

Rear light is a later one but the bracket is correct for the early style light unit.

CB72 rear light.jpg by graham.curtis, on Flickr

Early seat has bolt-on brackets. Rust looks bad but should be restorable.

CB72 Seat.jpg by graham.curtis, on Flickr

Both original badges have survived but will be replaced with modern replacements so that I can keep these safe.

CB72 Right badge.jpg by graham.curtis, on Flickr

Speedo is the early type with no high-beam indicator and no makers name at the bottom of the dial.

CB72 Speedo.jpg by graham.curtis, on Flickr

G-Man · Post by **G-Man** » Mon Jun 23, 2014 1:30 am

Some more details of the 1961 CB72

Gear linkage is different from later models. The gear lever has a flatter section and the clevises have a rounded end where the pin goes through. Makeshift extension is quite neat.

Gear linkage 2 by graham.curtis, on Flickr
Footrest hangers are thinner than later ones and have a smooth finish. These have survived without the usual cracks. Not bad for a 53 year old bike....

footrest hanger by graham.curtis, on Flickr

Rear shocks carry a remnant of the aluminium top cover and have the characteristic lozenge shape preload adjuster stop. Top collets and preload ring are steel compared with later bikes aluminium.

dampers by graham.curtis, on Flickr

Despite the terrible external state, the shock innards still contained oil and look to be in good shape apart from the damper rod which is rusty and pitted. You can just see traces of the original paint inside the top cover. The bike will be returned to its original blue.

1961 Rear Dampers by graham.curtis, on Flickr

G

G-Man · Post by **G-Man** » Mon Jun 23, 2014 1:41 am

I have managed to collect quite a few of the parts needed to get this bike back to original.

Alan Curtis came up with a really nice SLS brake plate and speedo drive, while a set of the big front forks and front hub came from Mister Monkeyclaw on eBay. The early speedo drive is unusual and drives an external tang via two slots in the hub.

SLS front brake by graham.curtis, on Flickr

Bill Silver came up with a NOS rear light assembly that will bolt straight on to my existing bracket. Alan also provided a wiring channel to convert the later type rear fender to an early type.

The early, larger diameter front fork needs all different shrouds. NOS lower shrouds and lower triple clamp came from CMS and the headlamp ears came from Nick at Ohio Cycle, courtesy of Conbs.

Front triple clamp by graham.curtis, on Flickr

Alan spotted these aluminium rear shock covers on a stand at the Stafford Classic bike show when I was in the USA. Thanks Alan! I had actually bought some material to make my own and might do that as a project later.

Shock Covers.jpg by graham.curtis, on Flickr

G-Man · Post by **G-Man** » Mon Jun 23, 2014 1:51 am

This weekend, I got the bike fully stripped down and got the frame and swing arm ready for blasting.

I was looking forward to seeing inside the engine because a) it was still turning over with compression despite 40 years in a damp shed with open carbs and b) it had a couple of tell-take screws in the oil gallery at the base of the cylinder.

Well there was interesting news. The head appears to be later with 12mm plugs and a later cam sprocket. I am now on the lookout for a good 10mm plug head after the one I bought via the 'net went astray.....

The reason for those little screws ( a modification to the oil feed to the liners ) turned out to be a full 350 kit, presumably supplied by Read Titan in the UK. Pistons are "forged-true" with the 'L' shaped (Dykes) top ring and the mod looks to be nicely done apart from the amateurish grinding work done on the crank case mouths to clear the big liners.

I am going to get the cases vapour blasted to see what general state they are in. Crank and gears look fine but there was a large quantity of sludge in the crank case and the oils slinger was full to bursting.

Crank and gears look to be in decent order.....

crank and gears by graham.curtis, on Flickr

Engine laid bare......

Engine stripped.jpg by graham.curtis, on Flickr

G

G-Man · Post by **G-Man** » Mon Jun 23, 2014 2:11 am

A quick update on some of the things I am still looking for....

My original grips look OK from a distance but both have had the ends cut away so i am on the lookout for a new set. Bill Silver says that Clauss Studios made some but we not happy with the result and these guys in Japan have them but will not export. Still looking....

http://www.ted-spl.com/forsale/parts/gr ... _grip.html

If you have any contacts in Japan - that would be very helpful.

A couple of years ago I picked up several early engine valley covers by mistake. I gave up any hope of finding a '61 bike and sold them all... I am now on the lookout for one. Such is life.

Also - that elusive aluminium front fender. I am not hopeful but you never know. Happy to do swaps.

When I get a moment, I'l have a look at the engine internals to assess their condition and similarity with later models.

G

Waveblaster · Post by **Waveblaster** » Mon Jun 23, 2014 9:39 am

Nice to see an early one the subject of a knowledgeable eye and restoration. Have you decided whether you will leave it with a 350 cc displacement?

regards

Greg