Rear Hub Identification

[JTR249]

741 Rear Hub B.jpg 741 Rear Hub C.jpg I recently bought a hub that I thought could be a 741 rear wheel hub with the sprocket mounted. The 741 service manual says PN 16040 is a 36 tooth rear sprocket as the correct part.
Well, when I received my hub and saw it was wrapped in the standard NOS military gauze and wax, I thought I had the correct part.
When I counted the teeth, I saw there are 50! Why would an NOS 741 have 50 teeth? Is this a side-car hub or another hub for a military 640 or similar bike?
Also, when I compared my hub with other online sources for sale, I see mine has five bolts and have nuts on one end. The other hubs listed online have six and do not show fasteners on the opposite end. The measurements are as follows; diameter of inner sprocket side 7 and 1/16", hub diameter = 2" exact, length of hub assembly is 6 and 3/8", diameter at the outer, small, spoke lacing end is 3 and 3/8".
Photos to follow.
-JR 741 Rear Hub D.jpg

[FLFD7]

JR,

Thats a weird hub, I think it’s Chief but 50 tooth sprocket? The center part of the hub looks too long as well.

What it’s not is a 741 hub.

Here is a pre 40 Sport Scout hub, very similar to the 741.

IMG_2164.jpeg IMG_2165.jpeg

The sprocket fits on the splines opposite the drum side.

On the Sport Scout the center section between the back of the brake drum and the flange for the spokes on the sprocket side is about 3 1/2 inches. On the 741 it is about 2 1/2 inches, noticeably narrower. (The spacers for the wheels much longer then Sport Scout). Here is some pictures of a 741 hub on one of my bikes…

IMG_2162.jpeg IMG_2163.jpeg

It’s hard to get pictures when it’s on a bike. Notice in the first picture there is a bit of a bulge in the casting where the sprocket mounts, another thing to look for to differentiate from regular Scouts.

So, sorry, whatever you got there is not 741.

Joe

[JTR249]

Thanks, Joe. I appreciate the help.
-JR

[JTR249]

What about this one?
Hub A.jpg Hub D.jpg Hub C.jpg

[FLFD7]

Pre 40 Sport Scout front hub….

[FLFD7]

From Greer’s website

The Sport Scout rear hub vs the 741 rear hub…

Sport Scout:
IMG_2168.jpeg

741:

IMG_2169.jpeg

See how much shorter the center hub section is on the 741, and notice the distance from the sprocket mounting splines to the spoke mounting flange, Sport Scout short, 741 long.

And the 741 has slotted spoke mounting holes on the sprocket side, the Sport Scout countersunk.

All credit to Jerry Greer Engineering for the drawings.

[FLFD7]

I was able to dig out a 741 rear to show difference to Sport Scout…

IMG_2171.jpeg IMG_2172.jpeg

Here you can see the different shapes and lengths on the sprocket side

IMG_2173.jpeg IMG_2174.jpeg

Here you can see the slotted spoke holes (741) vs the countersinks (Sport Scout)

[JTR249]

Much thanks again, Joe. I have the Greer manual, though sometimes sellers don't provide measurements.
The spoke holes information is also new to me. I could see the difference, though didn't know why.
-JR

[JTR249]

Here is one from Ziggy.
-JR 741 Rear Hub REF RZ A.jpg 741 Rear Hub REF RZ B.jpg

[FLFD7]

Bingo, there ya go. Looks like it has the hollow axle too….

[JTR249]

Thanks for confirming. I am talking to another seller right now and if they can't find one I will talk to Ziggy about this one.
Best.
-JR

[bernhardt]

Something else to watch out for on any splined hub, is spline wear. It's a common problem on old used hubs. In Joes post #7 above where he shows a picture of a 741, and a sport scout hub, notice the splines on the 741 hub. On this hub, the sprocket was loose, and it hammered back and forth under load. The result is a wear slot 90 deg from the spline, at each spline. In order to use this hub, you will have to weld up these slots, and turn them down to match the OD of the hub on a lathe.

[FLFD7]

The worn splines on the Sport Scout hub are why I didn't use it (I bought it with a sprocket mounted and didn't notice the damage). The sprocket gets loose cause that thin "nut" backs off and allows the sprocket to wobble a bit and wear out the splines. My friend Jules used to race Scouts and told me to drill and tap that "nut" and put in a short 4-40 set screw. Tighten the big round "nut" and then tighten the set screw against the sprocket, that'll keep pressure on the nut and keep it from backing off.

Joe

[JTR249]

Thanks to both of you for the tip. Instead of buying the hub, I was able to find a set of wheels.
I was fortunate to have found what I needed and a little more for not that much more on cost.
-JR