1961 CB72 Project

[G-Man]

Rich

The closer the better. I found that when you bump one end the other end gets affected too. At one stage I got one shaft within 0.0001 but couldn't keep it that way when I did the other end.

Some of the runout may be due to the inner wheels.

Once you work on a crank like this it feels like they are made of rubber.....😊

G

I got my rod side clearance adjusted to .007 and bumped it around until I had .0007" runout on one end and .0015 on the other. The wheel swash or wobble is under .0005. The high spot in both cases correspond to the pin location so I don't think there is much more I can do with it. For comparison I put another crank in between centers on my lathe and it had similar runout. I also checked runout by supporting the two center main bearings and checking the ends like Gram and got similar numbers to what I got not the lathe. Are the numbers I am getting reasonable for a street engine?

Thanks,
Rich

Last thread hijack...

[rpr851r]

Gram,
Yes, the fear of dropping one goes up after you spend a few hours trying to true it.

From what I can tell I am up against the inner wheels not being clocked perfectly since the high or low spots coincide with the crank pin location and I am not getting any wobble in the wheels. I didn't take the inner wheels off so any misalignment was there when I started.

Do you have a method for moving the inner wheels with the crank assembled? I am thinking of making a spanner to fit the large holes in the inner wheel. I haven't done the math but I think I only need to move one of them a small fraction of a degree to get the run-out under .001" on both ends. I do wonder if I move the inner wheels a touch if they won't just migrate back to where they were to start with.

Cheers,
Rich

[G-Man]

Rich

I was able to bump my inner wheel with a lump of alloy and the dead blow hammer, when I realized that there was some 'swash' on the centre section. I had the same problem as you on one side but sorting out the inner wheel did the trick. Like you, I worry about those things just migrating back but they will have the bearings for support once in the motor.

I had a Yamaha two stroke twin with .004" runout on one shaft and could feel the vibration. That wasn't one of my efforts but once it was trued properly it made a big difference.

The few Honda cranks I've checked show about 0.001 but you never know the history of these things, even in shipping.

When I get some more workshop time I'm going to make some more tooling to aid with trueing. My hydraulic press sprung a leak so I had to fix that before I could strip any more cranks.... :-)

G

Gram,
Yes, the fear of dropping one goes up after you spend a few hours trying to true it.

From what I can tell I am up against the inner wheels not being clocked perfectly since the high or low spots coincide with the crank pin location and I am not getting any wobble in the wheels. I didn't take the inner wheels off so any misalignment was there when I started.

Do you have a method for moving the inner wheels with the crank assembled? I am thinking of making a spanner to fit the large holes in the inner wheel. I haven't done the math but I think I only need to move one of them a small fraction of a degree to get the run-out under .001" on both ends. I do wonder if I move the inner wheels a touch if they won't just migrate back to where they were to start with.

Cheers,
Rich

[G-Man]

Finally back to the workshop this weekend to move the project along a bit. Haven't had much time in the UK, let alone home, in the last three months so it will be nice to pick something easy to work on to begin with.

On that note, I am looking for a pair of genuine 1961 wheel spindles. Both are hollow with the rear having a hole right through from the tommy-bar section to the threaded portion with the split pin. I think the front is just hollow at the tommy-bar section.

I would be interested in anything, whatever condition. If I can't find any I'll just machine up some later ones.

Thanks

G

[AlanW]

Hi G,
I have both spindles in my old racer, I can lend them to you if you want.
I am looking for cb77 barrels and pistons if any one out there can help.
Al.

[G-Man]

Alan

Thanks!

I think I have you covered on the barrels and pistons. Just need to check tomorrow. First time in the workshop for a while......

G

Hi G,
I have both spindles in my old racer, I can lend them to you if you want.
I am looking for cb77 barrels and pistons if any one out there can help.
Al.

[G-Man]

Having to work and travel is a real bind when you want to get on with projects. Being away means that I forget where I'd got to and where I put things.



I knew that I'd put the cam chain tensioner for this engine somewhere safe but it just wouldn't come out of hiding. I did happen across a box of rather ropey tensioners that I'd been bequeathed a while back. The correct one for this bike has the adjuster on the left while all the ones in my box had them on the right.

The correct one was in need of work so I thought I would just practise on one of the other grotty ones and hope that the missing one would turn up. I wanted to pull out the rubber wheel to clean it up. It is held in by a central shaft which is has two peened-over lugs at one end to secure it. I didn't fancy my chances at being able to put it back the way it came out so I ground off the two lugs flush with the side plate.



There is an oil hole through the central shaft which collects up oil with a little scoop at one end. The other end (between the peened lugs) is blocked with a little aluminum plug.

With the lugs ground off the central shaft comes out and releases the wheel with its tiny needle-roller and hardened inner sleeve.



My bearing felt a little rough and had a little degree of corrosion from water ingress. It looked a lot better after a trip to the ultrasonic bath and dip in clean oil.



Just in case, I checked the dimensions of the bearing. Unbelievably - it measures 3/4" OD by 9/16" ID x 5/8" wide and is available from my favorite bearing stockest at about $6. I ordered a few to get free postage.

The bore of the centre shaft with the little plug was 6mm and I realised, after searching my thread charts, that 6mm is the tapping size for M7. I happen to have some M7 taps (Honda disc brake bleed nupples used to be that size) so I made a little fixture and tapped the shaft.



I wanted to get the new surface of my cleaned-up wheel truly concentric with the shaft so I made a little tool to centre and clamp the wheel in my lathe.



It's easy to mount the wheel and using a sharp lathe tool I can clean up the surface and keep both sides of the wheel the same diameter.



eBay came up with some short M7 bolts and I may have to thin the heads down a little to get clearance. I also need to remember to make sure the bolt doesn't block the lube hole for the needle roller.

And, just as I was admiring my work, the original 1961 tensioner turned up. That will have to wait until next weekend.....



Those Cappelini tensioners were looking tempting but I reckon that I can now completely restore these tensioners with fresh bearings for less than $10 and about an hour of my time. A satisfying return to the workshop.

G