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new project: 1967 CB72

raydike

raydike

Member
Joined
Apr 2, 2023
Total Posts
38
Total likes
70
Location
Netherlands
Just bought myself a new project, a 1967 Honda CB72, originally from Switzerland. According to the title the last time the motorcycle passed the test was in 1980 so has not run for more than 40 years. The fenders and side panels have been chromed, not sure if I will keep it that way.
The oil was mostly gasoline due to a leaking gas tap. The seller ran it with this, hope he did not damage anything. I will slowly take it apart and make a list of the parts I will need. The front tire looks like the original one, since the bike has only run 20.000 km. Totally dry rotted of course. Engine and frame numbers match, that is nice. The seat has a strange shape, too wide at the rear, maybe aftermarket? Here is a picture:

CB72.jpg
 
Looks like you have the correct tank badges and installed on the correct side of the bike (personal pet peeve).
That and the proper mufflers is a really good start.
 
Looks like a great project! Are the frame and engine numbers exact match? If so that’s pretty rare.
 
Started dismantling the bike, already found some things that need fixing. The air filter rubbers are disintegrating, the wiring is a bit of a mess, the gear selector has a lot of play and a crack in the bushing for the kick starter, let's see what I can do about that.
Also found why the engine was full of gasoline. The previous owner had connected the overflow pipes of the carburetors to the air vents of the cylinder head.
crack.jpggarage.jpg
 
raydike said:
Also found why the engine was full of gasoline. The previous owner had connected the overflow pipes of the carburetors to the air vents of the cylinder head.
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Ugh, what a horrible misinterpretation of their function. Hopefully he didn't ride it with fuel-diluted oil.
 
Opened the engine, of course full of crud but the pistons appear to be relatively new 0.5 oversized ones. The cylinder walls look good too, no lip and no rust. Had a hard time getting the stuck cylinders off the block. A wood block and hammer did nothing.
Finally came up with a sort of pushing device: a 6mm bolt, a nut, a washer and a spacer. This did the trick without damaging anything.
IMG_20240927_213333_046.jpg
 
Started putting the engine back together. Put some spacers under the starter motor to take up the chain slack.
New oil seals and gaskets.
engine.jpg

Also used new clutch disks, same as for a 70's goldwing 1100. Used them in my 1961 dream too, work well.

clutch plates.jpg

And soldered in a new gauze filter for the oil pump. The old one had big holes in it. Gauze bought on ali express, super cheap.

oil filter.jpg
 
Nice work on the screen repair.
Thanks for the mention of the alternative clutch disks. My 305 Dream now has some non original disks that were found with extra PO parts, not sure what they were intended for originally but they fit and do have increased surface area and work well. Also thinner, allowing 6 friction discs, instead of 5.
It will be interesting to see if you are able to effect any repair on that cracked kickstart shaft bushing. Being that it is a hardened piece and cast in place on the cover. I know others have failed to be able to fix that and just replaced the cover.
qTC6PfLm.jpg
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Perhaps a thin steel or brass band of the proper dimensions could be swaged over the outside of that cracked kick shaft bushing prevent further cracking.
 
Nice bike, and a European version as well, as can be seen by the use of the steel air filter covers, low bars etc. Is the speedo / odo marked in km's as well ? The German / Dutch versions had winkers. Does the wire harness have light blue and orange wires? (for winkers).

The seat has a strange shape, too wide at the rear, maybe aftermarket?
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Could be, but could be original also, at least the seat pan. The cover is certainly self-made, or aftermarket, and the upholstering s bit strange (trapped). The rest of the bike seems original. It is either a very late version, as the fenders are chromed, or on of the PO's re-chromed them, because most of the CB72's have silver painted fenders, just like the side covers.
 
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Yes the speedo is the km version. No wires for indicators, also no indicator switch. The label on the wiring loom says 1965, so it is not the latest version. The fork stanchions are steel too, not aluminium like the later versions.
And yes the seat pan seems to be the original one. Found some steel tubing with 32mm ID that will fit around the cracked kick start bushing, maybe I will use that to repair it.
 
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A nice red "Honda special tool case" you have there, so to see with the special tools as well. I see you have the "hard to get" side stand and mount. Is it the original version ? Or the aftermarket version ? If it's the aftermarket version, be careful, these seem to damage easily, with the result that the bike will fall over.

Either the front fork is added later, since at 1965, the later aluminum front fork should be mounted, or the wire harness is a later one.
 
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Yes, well spotted. The Honda toolbox is actually for the 50cc bikes but has some useful tools, like the JIS screwdrivers. The side stand is aftermarket, bought in Thailand. I want a side stand because I plan on going on holiday with this bike, and then with all luggage on the back it is hard to get off the bike without falling over. This happened to me with another bike without side stand.
 
One of the cylinder studs had broken because of a stuck nut when I undid the cylinder head nuts.
I ordered a new one from CMSNL but to my surprise it was too short. First I thought I had reversed the lid on the cylinder head but then I found out the part numbers of the front and rear studs are interchanged in their parts list.
So now I had to order the correct one. Only one left in their stock and luckily not expensive.
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Started working on the carburetors, found the floats quite dented and leaking. Tried soldering the holes but there are too many so I just ordered replacements.
The main jets are size 85, I read they should be 100, maybe the previous owner tried to fix the rich running because of leaky floats by fitting smaller jets?
float.jpg
 
Today I took apart the front fork, the fork legs look good, only one tiny rust pit in one of the legs. Took one apart and replaced the seals. The other one refuses to come apart. It seems the previous owner used the wrong bolt (too long) to secure the mudguard and dented the lower fork leg.
I tried a moderate amount of force but to no avail. I don't want to destroy things so I am in doubt what to do next.. The lower triple tree bearing race also was stubborn. In the end I put a bead of weld on it to shrink it a bit and then managed to get it out.
IMG_20241108_144655_105.jpg
 
That used to happen a lot on the Triumph fork sliders back in the 1960s bikes. Supposedly the bulge from the too-long bolt can be removed with an adjustable reamer, but you have to get the stanchion tube out as your first challenge.
 
Been busy taking the brakes apart to clean and lubricate the moving parts. I wonder if the brake dust contains asbestos.
Used Dasty as detergent, very strong stuff. One of the return springs is mangled, new ones from CMS are quite expensive, let's see if I can find an alternative.
Also noticed that the nuts holding the pivot bolts of the brake shoes had been staked. Had to use a thread file to clean up the threads before unscrewing the bolts from the back plate.
brake shoes.jpgdasty.jpgclean.jpg
 
The break shoes contains asbestos if original (and that's the case looking at the Hm logo's at the rear brake panel). The front brake panel has aftermarket brake shoes, maybe more modern, but I would be carefully with the dust. Never blow it away, unless you're outside and wear a mask that blocks those particles, better clean them in a bucket of water with Dasty and brush, keeping the parts under water the whole time.

The front break shoes are a bit thin, maybe replace them anyway ?
 
Started putting things back together, had to take a longer bolt for the side stand, improvised a bit with a piece of tubing.
Put some wax in the fenders to prevent rust. Just noticed I put the aluminium brackets on the wrong way round, haha.
Like my easy rider poster?
opbouwen.jpgbout.jpg
 
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raydike said:
Started putting things back together, had to take a longer bolt for the side stand, improvised a bit with a piece of tubing.
Put some wax in the fenders to prevent rust. Just noticed I put the aluminium brackets on the wrong way round, haha.
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That will teach you to work on the bike upside down, LOL
raydike said:
Like my easy rider poster?
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Looks appropriately faded for its age. If only it wasn't on the other side of the room in a picture that won't enlarge... :giggle:
 
For your pleasure, the whole image. Note the missing front brake on Peter Fonda's bike.
I remember seeing the Easy Rider movie in high school when I was 16 or 17. It blew me away.
I totally identified with Fonda and Hopper. There was a girl I fancied that saw the movie with me, she hated it. What a deception. End of crush haha.


aesy rider.jpg
 
raydike said:
For your pleasure, the whole image. Note the missing front brake on Peter Fonda's bike.
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Yes, one of the many things I dislike about hard core choppers, they somehow think that with the majority of the weight shifted toward the rear of the bike that having only a rear brake is enough.
raydike said:
End of crush haha.
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I hate it when that happens!
 
In the manual it says to put 220cc of white spindle oil in each fork leg
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Instead of a fixed volume, it's better to measure the height of the oil level (air chamber), and set both legs exactly to the same air chamber.
 
So fill one leg with the amount of oil you / Honda prefer, measure the air chamber, and fill the other leg with oil to the exact same height. The weight of fork oil depends on your weight, your riding style and what you prefer. Me, as my weight is 80 kg, and like a stiffer front fork, use 10W and an air chamber of 100 mm on the CB72.

The air chamber is measured with the fork leg 100% compressed, no spring mounted, and from the top of the leg to the fluid level. If you already mounted the springs, then fill one leg with the volume mentioned in your earlier post, and adjust the level from the other leg accordingly. Make sure you use the specifications from the correct fork, since early and late forks use different volumes.
 
Interesting, so now I have to figure out how much oil I have to put in. I asked chatGPT, it says 150cc but I guess that's not a very reliable reply ;)
 
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Today managed to break an original Denso coil when trying to unscrew one of the nuts, bummer.. Maybe I can glue it together.

IMG_20241124_135407_369.jpg
 
Yes, you can, just use cyanoacrylate, it works. About the forks, just put 180 cc in, and go from there, are the forks too soft, just change the height of the chamber. If the volume is 150 cc for the steel forks, it is for the average lighter Japanese citizen.
 
Glued the coil, seems to work ok. I wanted to fit the new air filters I bought but they are different, bigger than the old ones. Maybe I can squeeze them in the air boxes but maybe the air flow will be restricted...
Also I forgot where this earth strap goes, as I remember near the coils but not sure. Cannot find it in the diagrams.
air filters.jpgearth strap.jpg
 
Just checked CMSNL, in their picture of the air filters there are no air boxes like the one in my previous post. It seems the Swiss version (like the one I have) is different. They sell the left filter for 75 euro, but the right filter is no longer available.honda-cb72-hawk-60-61-62-63-64i-64ii-general-export-142683-air-cleaner-tool_bigma000099f09_b324.gif
 
raydike said:
Just checked CMSNL, in their picture of the air filters there are no air boxes like the one in my previous post. It seems the Swiss version (like the one I have) is different. They sell the left filter for 75 euro, but the right filter is no longer available.
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Did you check the part number at Davis Silver Spares? They don't show up in part number searches very often, so go here and check:

www.davidsilverspares.com

David Silver Spares

David Silver Spares Honda Part Number Search
www.davidsilverspares.com
 
Thanks for the link, They can get the left filter on request (maybe at CMS?) but the right one is unavailable. I guess I will have to improvise a bit.
 
The ground strap is from the headlight area best I can tell from the parts fiche, though I'm not sure where it attaches. #23 here

honda-cb72-hawk-1961-usa-headlightmetertaillight_bighu0097f8315_c7f3.gif
 
Ah, thank you, I guess it is for connecting the front fork to the frame to prevent current flowing through the bearings.
 
Just checked CMSNL, in their picture of the air filters there are no air boxes like the one in my previous post. It seems the Swiss version (like the one I have) is different. They sell the left filter for 75 euro, but the right filter is no longer available.
Click to expand...

These boxes where only used in Germany and Zwitserland, the rest of the world had to do without them. The Dutch bikes are more or less the same as the German ones, so also boxes around the air filters.

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Today worked on the electrics, made a little shelf for the ignition and voltage regulator. The rectifier/regulator is from a yamaha. It's for a three phase alternator but I will just use two of the three wires. Should work fine, it does on my dream.
I fitted a lithium iron phosphate battery, it is a bit smaller so the regulator and ignition fit above it.
ignition.jpg
 
raydike said:
First start with the electronic ignition. Still have to fit the mufflers. I put some Owatrol rust inhibiter in them, that has to dry.
Here a youtube link:
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Thanks, I've not seen one in action. With electronic advance, do you disable the centrifugal unit?
 
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