520 conversion

I converted my E-850 with a CNW kit which was the epitomy of bolt-on and high quality, sealed bearings and all. I will be converting my '72 when I get to that stage and wanted to ask the forum if members knew of any shortcuts to doing the conversion, more specifically:

1) Are 520 friendly counter shaft sprockets available off the shelf or do you need to machine standard Commando sprockets?

2) Can the rear sprocket be turned down by any competent machinist? And does the 1/8" have to come off both sides equally or can it comfortably come off one side without causing un-due chain stress/wear, given the run?

3) I could see if both sprockets had to be machined that you could take 1/8" off either side as long as you were consistent.

With many thanks,

RS

Hi RS,
I did the conversion a number of years ago before any kits (that I know of) were available. I turned both sides of each sprocket (seemed like the best approach???) on a lathe that I am sure is older than any two (possibly three) board members combined. I actually held my bench grinder against the turning sprocket until I reached the desired width.
Regarding the front sprocket, Norton Atlas and I believe Dominator models are 520 sprockets and fit on Commandos. Other than CNW the only other supplier that I know that sells narrowed rear sprockets is www.clubmanracing.com in CT.

GB

If your lathe is older than me, it must be powered by a rope tied to a tree branch with a foot pedal and a crankwheel.

1) Are 520 friendly counter shaft sprockets available off the shelf or do you need to machine standard Commando sprockets?

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Both Norvil and RGM do 1/4" front sprockets.

2) Can the rear sprocket be turned down by any competent machinist? And does the 1/8" have to come off both sides equally or can it comfortably come off one side without causing un-due chain stress/wear, given the run?

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It all comes off the outside. If you use an old sprocket it's worth having it rehardened. Also needs profiling to match the inside, slight chamfer but not sure of the angle.
I did this a couple of years ago and I think it is worthwhile, less adjustments and a longer lasting chain. It is stiff when cold and probably saps some power but overall it's good. You can always use a fancy low friction X ring chain. If you want to keep the split link use a DID 'O' ring as it seems easier to find semi pressed split links for this brand. It still needs vicegrips to assemble the link but will disassemble without grinding rivets etc.

Keith1069 wrote;

Both Norvil and RGM do 1/4" front sprockets.

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Andover Norton also supply them.

Old Britts has them as well and can machine your old rear sprocket or supply new ones. They can also provide parts or complete kits a la CNW.

I'll be doing the 520 mod sometime in the next few months; I think it's well worthwhile.

It definitely is one of the better mods. When I did mine I sent the drum, brake shoes and backing plate to Vintage brake. Wow, what a rear brake now!

I thought the 520 front sprockets were just off the older Nortons?

A 530 chain on a Commando is like the flea with a hard-on, floating downriver on his back, hollering, " Raise the drawbridge".