Reaming cam bushes on a single

[Keith.owen]

Hi Simon,
This seems more encouraging.

Interestingly concerning the clearance in a worn bush, it would, I imagine not wear in a linear fashion, so it would depend how it is measured?

Keith

[cmfalco]

I just made a set of CA104 aluminium bronze bearings for this location..

For what it's worth, after considering all of the possibilities, a few weeks ago I made a set of C93200 (SAE 660; tensile strength 35 ksi) camshaft bushes for my 1928 Model C. Al bronze is a lot stronger (100 ksi), but for this lightly loaded application stronger isn't necessarily better because stronger comes with other properties that aren't necessarily ideal (e.g. worse ability to conform to journal irregularities and embed grit). SAE 660 is a "standard" bush material for such applications in part because it is more tolerant than most other bronzes of lubrication issues. I made the mainshaft bush from the stronger C54400 phosphor bronze (55 ksi) because I felt its properties made it a better choice for this application than the even-stronger Al bronze.

[Simon.Gardiner]

Keith: I guess it might wear linearly (uniformly?), I've got a camshaft with one of the spindles appreciably undersize but it's still parallel and without any scoring - although the dimensions might be down to how it left the production line rather than wear. I think the main issue for these bushes/spindles is whether they're scored or not.

CMF: I think that BSA jig is the one also intended for idler and camshaft bushes. From comments I've seen elsewhere you might have the only one they made! There must have been a special reamer with it for the cam bushes as the 3rd bush is in a blind hole across in the drive-side crankcase with maybe 1/2" clearance between the end of bush and the bottom of the hole, needs something with very little 'lead' and probably rather longer than a standard reamer. (Also, the indexing locations for the jig in the timing-side crankcase need to be pretty accurate!!)

SG

[cmfalco]

From comments I've seen elsewhere you might have the only one they made! There must have been a special reamer with it for the cam bushes as the 3rd bush is in a blind hole ...(Also, the indexing locations for the jig in the timing-side crankcase need to be pretty accurate!!)

Yes, from comments I've seen I may well have the only one in existence. The reamer that BSA shows in an illustration is of the shell type, which is typically used only for larger diameters, but without a projecting arbor shaft.

Although I have an A10 I've never held the jig against it to see in detail how it is aligned. Presumably, the projecting 1/4" pegs at the upper right and lower left of the jig fit into alignment holes on the case. I have a mill, which is what I would use if I needed to ream those bushes, but that jig would be a lot better than nothing for a mechanic in a motorcycle shop in the middle of nowhere in the 1950s. Assuming the alignment holes were accurately drilled at the factory...

[Keith.owen]

Hi,
I have ordered a 0.75" reamer and shall give it a try (rather than use one of my adjustable reamers).

I have got some spare bushes so if the worst happens..................

Keith

[paul.jameson]

Do let us know how you get on with this. I have to say I was tempted to go for the option of making a new plain bush, reaming it to size with an adjustable reamer and then cutting the slot with a hacksaw blade.

[Keith.owen]

Hi Paul,
I will let you know. I shall be attacking the bushes this weekend. I'm hoping to finish of the CP box I'm working on during the remaining evenings of this week. I fitted new bushes to the 4th gear and decided that they didn't really need any further attention. I drove them in with the aid of my vice and some wooden cheeks. Just waiting for some more loctite to fix the casing studs..............isn't it always the same? I had two bottles and both were empty!! Grrrr....

Keith

[pappleton]

Hi Keith,
Just looked in Waller, clearance should be .001-.0015"
BR, Paul

[Keith.owen]

Hi Paul,
It is misleading in that it states that the bush should be 0.75" and the cam spindle undersize from 0.7485 to 0.749. Although when talking of the bush size it gives no tolerances.

I guess this is down to the wear expected on the spindle to be minimal and the spindle tolerances given are manufacturing.

I don't know. I am only guessing!!

Keith

[pappleton]

I wonder why the bush in the crankcase doesn't have an oil hole, yet the casting has a depression just above the bush, which looks to be designed for a hole?
BR, Paul