Fitting 850 swing arm to '70 bike

The original swing arm on my '70 is bent. I have an unused 850 version ( pn 06-5888). If I fit the 850 swing arm do I need to use the short spindle, wicks, 850 end caps, etc. or can I use the long 750 style spindle, spoke, and end caps ?

Thanks

Greg

You can use your on-hand 750 bits. Have you done the spindle-fix operation ?

Assuming width between the bush mounting holes is the same then I assume you'd have to use the 850 spindle etc. Although you're better off throwing away the wicks and simply filling the reservoir with oil after sealing the end caps and providing a method for adding oil as req.

I fitted two 850 arms to 2 Combat w/o an issue using the 750 end cap 'seals' no problemo and only later learned 850 had different stuff involved. Both also had Kugler collars installed, after fiddling the fit and bolts aim for best advantage. Used the bigger OD spindle and hand reamed bush for nice fit w/o regrad to pourous bronze as non issue as long as some type of lube covering spindle enough not to rust, then wear.

hobot said:

I fitted two 850 arms to 2 Combat w/o an issue using the 750 end cap 'seals' no problemo and only later learned 850 had different stuff involved.

Click to expand...

But then, only the late 850 Mk2/2A and all Mk3 swinging arms had the shorter "sealed" bush/spindle assembly.

The part number (06-5888) quoted by gjr is the 850 Mk3 item.

Torontonian said:

You can use your on-hand 750 bits. Have you done the spindle-fix operation ?

Click to expand...

I went the way of welding nuts to the cradle tube and using bolts to fix the position of the spindle.

Greg

The part number for the swing arm that you used in your initial post (p/n 06-5888) is for a Norton 850 Mark III Commando which of course would not work at all on the earlier Commandos because of the Mark III's different wheel design and swing arm wheel attach points. The part number that you can use would be 06-4539 which would be the one you would want to use because it allows you to use the rest of the 750 components (seals, bushings, spindle, etc.). This swing arm was used on the 850 Mark I/IA's and the earlier Mark II/IIA's. Later in the Mark II/IIA's production (I think around engine number 314xxx) the swing arm had been modified to use welsh plugs and shorter bronze bushings. For this swing arm I do not know what the part number is, my Mark II/IIA super session parts list has not been revised for the later motorcycles. The later Mark II/IIA swing arms are identified by having a step bore in the pivot end of about .300 of an inch where the welsh plug would go. If you use this swing arm you need to use the welsh plugs, shorter bushings, shorter spindle, etc. because of the step bore.

Old Brits surprisingly offers a service to convert the earlier swing arms to the later Mark II/IIA and Mark III design. Makes me wonder how many people even bothered doing that. He shows a picture of the differences between both swing arms.
Picture link from Old Brits:
http://www.oldbritts.com/image/38_600206a.jpg

The swing arm pivot seals ( p/n 065227) used in the later Mark II/IIA type are pretty expensive and easily damaged while installing the swing arm. For my bike I fabricated a "dummy spindle" from aluminum alloy that was the same width as the cradle. I believe this helped the seal from being cut from the edge of the spindle bore. Once the swing arm is in position the 'dummy spindle' is removed and the real spindle can be installed.

My post probably has nothing to do with this thread. But my bike sat for 35 years in a damp environment before I tore it down. It is a '74 850 and had the wicks and welsh plugs on the swingarm. After seeing the beautiful condition of the internal parts after all that time I would have a hard time not using those same parts on anything I was going to ride. My spindle slid out of the swingarm with a heck of a lot less trouble than my '72 750 which had been stored in a warm and dry location for about half the same period. I know it proves nothing to anybody but me.

Russ