1961 CB72 Project

[G-Man]

Back from my US trip now and able to check out the parts I brought back.

Here are my NOS brake shoes which, thankfully, match up perfectly with the SLS originals. They just have new, thicker linings.....

I think I paid about $25 for the pair so a good purchase.

G

brake shoes NOS by graham.curtis, on Flickr


Brake Shoe Comparison by graham.curtis, on Flickr

[hondauser]

Hy G-man,
I have't made the P&P yet ;
I hesitate between a double wall strong cardboard box or à heavier Wood crate !!!

What do u think about ???

MK ,

[G-Man]

Hi Michel

Maybe a box with the head in it. Then some more packing and another box?

G

[G-Man]

I picked up a pile of newly bead blasted parts this morning and had to quickly give them a treatment with phosphoric acid rust killer to prevent the dreaded corrosion immediately taking hold.


1961 CB72 Parts blasted by graham.curtis, on Flickr


For such a rusty bike I was surprised how good the parts turned out. Only the tank seems to have any real corrosion damage and that seems to have rusted from the outside in. The inside looks pretty good with no rust but I still have a few holes to fix.

Holes in tank by graham.curtis, on Flickr

Honda apparently used copper or bronze rivets to attach the aluminium CB72 fenders to the brackets and this seems to have carried over to my steel version. Interestingly CL aluminium fenders use aluminium rivets. Not too sure why the thinking was different. Notice the single rivet at the edge of the fender bracket. Later fenders have a pair at each edge of the centre bracket.

Front Fender rivets by graham.curtis, on Flickr


I couldn't resist just popping the engine in the frame to see how it would all look.....

1961 CB72 frame with engine by graham.curtis, on Flickr


The center stand needs some work and is smaller than later stands so needs fixing rather than replacing.

I will soon have run out of parts to clean and de-rust. Re-assembly will begin after my vacation in early September....

G

[G-Man]

Just received this early rear brake plate from the ever helpful Gordon Brown. I was told that these did not fit later hubs and was keen to find out how that was and what could be done. I think I have worked it out now.

Here is the plate with the different torque anchor.....

Early plate.jpg by graham.curtis, on Flickr

Here it is fitted to a late hub. Despite the smaller diameter, it won't rotate freely and you can see that there is a 3mm clearance around the outside.

Early plate - late hub by graham.curtis, on Flickr


Here's the difference. The later plate (top) has a double flange and the groove between them accepts the edge of the brake drum liner to form a labyrinth seal to keep dust in and rain out. The early plate has a single flange and, because of the smaller diameter, sits directly on top of the brake drum liner.

Brake Plate Differences by graham.curtis, on Flickr


Here's what a late plate with matching hub looks like. Very small clearance....

late plate and hub by graham.curtis, on Flickr

So. What's the answer? The 'correct' answer is to find a matching hub but I may have to either space the brake plate out a little or machine the edge of the brake drum liner. Without the correct hub I would think that there will be a gap and I'm not sure that I will be happy with that....

G

[G-Man]

I ordered some early cylinder base gaskets on eBay recently and despite the picture showing the correct gasket the seller sent me the later ones and claimed that they superseded the correct ones.

There is quite a critical difference in these early "Breather Tower" engines and I am not happy using later gaskets whatever the technical documentation says.

This is an early 1960 Dream crankcase - very similar to my 1961 CB72....

Early (000 type) engine by graham.curtis, on Flickr


Later engines have an extra oil hole to route the oil supply equally via both front studs. You can see that on this later gasket. This one is the 010 part.

-010 Gasket.jpg by graham.curtis, on Flickr

The correct gasket doesn't have this hole and leaves open the area around the left stud which then allows oil flow to the right stud via the oil gallery. This is the 000 part.

I wonder if these early engines suffered oil starvation to the right cam and rockers?

-000 Gasket by graham.curtis, on Flickr


G

[G-Man]

I had a stroke of luck this week. Alan Curtis came up with an early rear hub to match my brake plate. That means that I now have a complete set of wheels and brakes for my project.

This one is the perfect diameter match for the hub and the brake drum liner is much lower in the hub than later versions.

There is some cleaning up to do and the brake drum will need skimming but I am very happy. Thanks Alan!

G

Rear Hub 1 by graham.curtis, on Flickr


Rear Hub 2 by graham.curtis, on Flickr