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CB72 Crank Rebuild

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G-Man
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CB72 Crank Rebuild

Post by G-Man » Fri Nov 15, 2019 2:09 am

A while back I bought a little Honda C110 project from a guy in Essex, UK and he had an old CB72 racer on his bench. He inherited the bike from a old friend who had last raced the bike in Singapore in the 1970s.

The crankshaft looked in a shocking state and he asked me if I knew anyone who could take it on. All bearings were locked solid and it didn't look recoverable.

I made a start and pulled it apart, not expecting much.

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Although the big ends would not rotate on their pins, they did come apart.

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The rollers were stuck in the big end cages and had to be physically pushed out after soaking in a hot ultrasonic bath.

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I realised, eventually that this thing was stuck together with old Cartrol R vegetable oil which was popular back in those days.

Multiple visits to the bead blaster and ultrasonic cleaner were required to get it cleaned up, but all bearing surfaces wre perfect. As usual with these cranks, the sludge traps in the big end pins and the centrifuges which feed oil to the big ends wre clogged with dirt which had to be drilled and scraped out.

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This stuff will eventually reduce or even block the feed to the bearings so it needs to be removed.

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After several hours of cleaning, I could get ready to re-assemble.

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The centre-section, in particular, needs careful alighment so I used the fixture I made for my own CB72 crank to keep all of the parts lined up.

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With that done, pressing the outer webs on is just a matter of lining them up as closely as possible before final truing up.

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It's necessary to get the outer shafts trued to within 0.001" and I do this by sitting the crank, without outer bearings in a set of crank cases and checking runout with a good dial gauge. Corrections are made with a good 'dead blow' mallet.

This one went together without any new parts. Everything was in spec with no visible damage.

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A good day in the office..... :-)

G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

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brewsky
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Post by brewsky » Fri Nov 15, 2019 8:02 am

Impressive, G!

How about some pics of the C110?

That was my first street legal model!

Imagec110 1 by bruce leedy, on Flickr
66 dream, 78 cb750k, 02fz1, 09 wing

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Muddy
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Location: Sunshine Coast, QLD, Australia

Post by Muddy » Fri Nov 15, 2019 2:37 pm

Very nice work G-man!
Thanks.

Regards

Muddy

'64 C72
'63 C72

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G-Man
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Post by G-Man » Fri Nov 15, 2019 5:42 pm

Muddy

I used to ride a C110 around the farm when I was a kid.

I picked up this non-runner last year and tidied it up as a 'rolling restoration'. It hadn't run since 1983.

The engine and wheels have been rebuilt and one or two bts of chrome have been re-plated. The rest is just cleaned and polished.

It's a real laugh, riding it around the lanes. I have (as you do) acquired two more for full restoration.

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Out and about.....

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Filling up...

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At the shops....

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G
brewsky wrote:Impressive, G!

How about some pics of the C110?

That was my first street legal model!

Imagec110 1 by bruce leedy, on Flickr
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

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brewsky
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Location: Princeton, WV

Post by brewsky » Sat Nov 16, 2019 8:24 am

Thanks for the pics, G.

I would love to find another one to pick up locally.
66 dream, 78 cb750k, 02fz1, 09 wing

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G-Man
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Post by G-Man » Sat Nov 16, 2019 3:08 pm

Brewsky

You're welcome!

I hurt my leg / back earlier this year and it has been great fun playing with such a lightweight bike.

G
brewsky wrote:Thanks for the pics, G.

I would love to find another one to pick up locally.
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

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brewsky
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Posts: 1816
Joined: Wed Jul 23, 2008 5:21 am
Location: Princeton, WV

Post by brewsky » Sun Nov 17, 2019 5:44 am

I hear you!

Wait 'till the time comes that you need grease fittings for all your joints!

I can have almost as much fun on my Sparta moped, and don't have to worry as much about my hip or knee giving out whenever I stop! It's just not suitable for mixing with traffic.

I don't remember having any problem keeping up with local traffic on the 110 though. It may have been a 4 speed trans, though I'm not sure about that.
66 dream, 78 cb750k, 02fz1, 09 wing

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