1961 CB72 Project

G-Man · Post by **G-Man** » Mon Mar 09, 2015 3:27 pm

While I am waiting for the piece of ground steel bar I need to finish the crank jig I thought that I would have a go with the little big-end roller lapping tool that I made. I bought a large volume of 2.5mm rollers but they are a tad too long at 13.8mm compared with the Honda rollers at 13.5mm.

The rollers are loaded into the tool then it is inverted and applied to very fine abrasive paper on a smooth surface. Once half the material is removed the rollers are emptied out, turned over and the process repeated. After around 10-15 minutes the rollers all fitted nicely in my cage.

Just to make sure that all was OK a set of rollers was greased and loaded into the cage in one of my rods.

This was much simpler to do than I expected and much, much cheaper than trying to use those almost unobtainable Honda rollers.

If I am going to re-use these rods, I will have to sort out the small ends. The bore looks like it has had a hard life and I am going to experiment with putting a bronze bush in the eye. A lot easier job to do when the rods are off the crank.

G

alan curtis · Post by **alan curtis** » Mon Mar 09, 2015 5:03 pm

Graham, you are bringing new levels to the home workshop, I am amazed at what you are turning out. fantastic pics, top job. thanks for your help...

G-Man · Post by **G-Man** » Mon Mar 09, 2015 5:10 pm

Alan

Thanks! There are plenty of knowledgeable and helpful people on this forum and I have learned from many. I am just adding to the pool and having some fun in the process....

I'm just an enthusiastic amateur trying to avoid becoming an unenthusiastic professional. :-)

G

G-Man · Post by **G-Man** » Wed Mar 11, 2015 2:38 pm

The last piece of my jig 'jigsaw' arrived and I was able to check alignment and move on to the next part.

Just need to shorten those columns and make the part which will index the timing sprocket. There are 16 teeth on the crank sprocket which means that there will be a corresponding tooth at 90 degree intervals.

In the pic of this crank the sprocket tooth lines up nicely with the crankpin but I will pick up one of the teeth at 90 degrees to this on my fixture to make getting the pin in easier.

Getting slowly closer.......

G

G-Man · Post by **G-Man** » Sat Mar 14, 2015 1:53 pm

Back in the workshop today, making the indexing part of the fixture. This part is made from two pieces of aluminium bolted together before boring the major holes. This is because it will be trapped on the crankshaft once the wheels are pressed back onto the centre section.

The big hole in the centre has to accommodate both the sprocket and the oil pump gear, both different diameters to make life a little more interesting.

To index the sprocket, I made a little pin from an M6 bolt and filed it to make it fit the space between two sprocket teeth.

Because I opted to go between the teeth rather than pick up one of the teeth, my pin is offset 11.25 degrees (½ a tooth). This keeps the actual point of the tooth set at Top Dead Centre.

And here is another trial assembly of the pieces

Still a couple of jobs to do before I can put the crank back together. The thickness of this piece needs trimming a little as it is wider than the available space between the bearings.

I have to make some new plugs to block up the big end oil galleries and the small ends in the rods need sorting.

G

sarals · Post by **sarals** » Sat Mar 14, 2015 4:03 pm

Good stuff, Graham! It's really fun to watch a master machinist at work. Clever ideas, simple approach, I am in awe!

jerry · Post by **jerry** » Sat Mar 14, 2015 4:12 pm

"On Ya G Man." I like that you are using your most valuable asset. I wish more would do the same. All the best Jerry