1961 CB72 Project

[AlanW]

G, I am still on the right side of the grass thanks, I have an early clutch cover if you need it and also still have early wheel spindles that just need rechrome.
I will be at Stafford on the Saturday, hope to see you there.
Al.

[G-Man]

Alan

Yes - should be there. I'll bring your barrel and cam chain tensioner along.....

Definitely need those spindles. :-)

G

[G-Man]

Another weekend approaches and I've come up with another mini project. I lost the main kickstarter gear for the '61 project and set about finding another, only to find that's not an easy task these days.

Fortunately, I was able to come up with a slightly-mangled specimen from a good friend, but it seemed to me that not everyone is going to be lucky trying to find this part. I set about finding something that could be used as a replacement. After a quick email to Dennis Lodge about the similarities between CB72 and CB750 kickstart splines he came up with a NOS CB350 / SL350 shaft that looked like it could be re-purposed. Here it is alongside the CB72 kickstart gear and pinion.



My idea is to take a spare pinion (the one with the spring slot) and bore it out to take the CB350 shaft as an interference fit. Once the two are united I will weld the back side and, hopefully, make it strong enough to operate the kickstart. The CB350 shaft is slightly larger diameter so I will have to bore the bush out in the case slightly.

Happily the working part of the shaft is almost identical in length so the modification should be quite simple.



I will have to put in a new circlip groove but that should be pretty straightforward.

Well, that's the plan.....

G

[G-Man]

The first job was to do a little measuring, to transfer details to the CB350 shaft. There is a circlip groove at the end of the spline whicjh holds the gear in place.



With the same parting tool, I cut the groove and cut the shaft to length. The shaft also needed reducing in diameter as it was 1mm larger than the CB72 one. I chose to leave it a little bit o/s so that it would be a snug fit in the slightly slack bush.



Here is my new shaft alongside an original.



The pinion gear was hardened around the spline area so it needed annealing. I heated the part around the center and hoped that the heat did not penetrete too far into the tooth area.



With the gear softened it could be mounted in the lathe via its own shaft and allowed me to drill and bore an accurate hole.



Here is the shaft and pinion ready to be pressed together.



Here is my new gear alongside the original.



I just need to run a fillet of weld around the boss area at the back to make a permanent and strong job. After this I have parts to do three more. :-)




G

[G-Man]

It's difficult to stop when you get started.....

Two more gears ready for welding.

It's dark outside where I like to do my welding so that's a job for Valentine's Day.......



G

[sixtiescycle]

When you're on a roll why stop! Nice work!!!!!

[G-Man]

Thanks Dick.

Sometimes things just fall into place.

G

When you're on a roll why stop! Nice work!!!!!