1961 CB72 Project
G-man,
I am very impressed indeed with this sharing of the CB72 rebuild. I am presently stripping my 1965 CB77 motor to replace a damaged kick start shaft. I noticed that you checked whether offset cutters were needed when you re-assembled the gearbox. Any tips you can give on the process to make this check would be much appreciated! Thanks again for this excellent record of your restoration. Gordon Hi Gordon
Thanks for your kind comments. I am not an expert on these engines - there are others that have rebuilt many more than I ever will. All I am trying to do is share some of the details of the early bikes compared with the more common, later versions, and show what I find. My perspective is not that of a CB72/77 expert but as an engineer of 35 years looking at a piece of engineering. What I was looking at was the dog engagement for the two gears (one on each shaft) that are attached by the cotters. The dogs are 'undercut' which means that they look like a dovetail and should pull the gears closer when torque is transmitted. If the engagement looks like it insuffiecient to get that dovetail action started then the cotters place the gear a little farther along the shaft to give a little more engagement. One of mine looks good and the other looks a little borderline to me. I'll get some pictures today if I can but after that I will be away for a couple of days, so be patient. 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 I was asked if I could show a close-up of how the right-hand main bearing gets its oil feed. Unlike the later cases which are designed to feed oil directly into the roller bearing these early engines feed oil to the outside of the bearing. The big oil seal closes off the chamber. The feed is ported through from a channel inside of the case rather than from above like the later bikes.
 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 For those who followed my little saga on crank rebuilding I posted a picture a little while back showing my rust-damaged CB77 engine. The crank was in a pretty sorry state with most of the bearings rusted solid. I cleaned it up a couple of years ago but it was still pretty horrible.
This is how it looked in the engine......  And when I found it yesterday..  It came apart quite easily and I knew that it was scrap but I gave the parts a clean up and discovered some interesting details which made the excercise worthwhile..... Here is the center shaft and one connecting rod.  Notice that the centre shaft has been repaired at some time by turning it down and adding two hardened sleeves for the rollers to run on. One of the sleeves came off when I pulled the bearing off but the other is on there for good. And, get this, someone had rebuilt the engine with 'race kit' single roller big end cages. Normally these have wide slots with two rollers per slot. The race kit bearings have fewer rollers but they run singly to reduce the effect of rollers rubbing together.  This crank must have been quite a mess as the little ends have also been bushed. Very similar to my own modification but a little thicker. These bushes are still a great fit on the pin and show no damage or wear like most Honda 'steel on steel' little ends.  And here's the center shaft underneath one of those sleeves. It looks like the excercise to press on the sleeve didn't go too well as the metal looks like it has been scored as the bush was pressed on. It went unnoticed for around 30 years, though..... :-)  And the other side with bush still intact but badly rust damaged...  Lastly, here is the inside of the most rusty big end. The corrosion has eaten a good 1/2mm or so. It wont be pressed back into service any time soon but it might become the subject of some experimental work later. My next door neighbour is a metallurgist at Rolls Royce and I am tempted to cut the big end eye in half to look at the case-hardening thickness that Honda achieved. If you polish and etch the cut surface you can see the change in crystalline structure created by the hardening process. I remember doing that in my University days....  G
Last edited by G-Man on Sat Apr 11, 2015 3:16 am, edited 1 time in total.
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F Jerry
Always happy to make people smile - it's the best therapy! :-) The pictures of your race bikes and engines always make me smile. Quoting John Cleese "Never confuse seriousness with solemnity"..... 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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