Brake drum B4-463

The WD16H had the 43t rear chainwheel and there were so many NOS spares available for years that they probably became the standard replacement when Norton stopped producing the older types (I wonder if they ever made them at Plumstead ?)

The modern pattern industry seems to have picked up on the 43t as the norm.

You may need a half link in your chain (which will certainly need replacing anyway!) and the bike will be a little lower-geared. If you're not on fast roads, it shouldn't be too noticeable. Going up a tooth at the front will over-compensate for it.

What size do you have on the front at present ?

I think it would have had a 43t sprocket originally. The reality is that one tooth difference on the rear sprocket is going to make very little difference on the road. You are gearing it down slightly which means slightly more revs for a given speed. By my dodgy math's you're changing the gearing by 2% so it's unlikely you'll notice much difference.

You may need a longer chain though and if you're changing the sprocket it would be false economy to not replace the chain. Ideally you should change the front sprocket too, so that everything is new.

Ian

P.S. Richard beat me to it, must type faster.

I would stick with the standard 19t gearbox sprocket but check your engine sprocket to make sure that it has a decent solo size...at leat 20t, perhaps 21t

Hi Bryon,

The 43 tooth sprocket was fitted across the road-going range for the 1953 season which was when the ES2 first used the swinging arm frame which used the same wheel and sprocket as the rigid frame bikesthat were still being made at that time. Your bike should have plunger type suspension and have the upright gearbox. Both of your sprockets will be different to the 1953 ES2 although the gearbox one is 19t on both but the upright type has a wider boss than the later laydown type. The back wheel sprocket is different on the plunger frame, so what this implies is that Nortons didn't make a 43t plunger type sprocket while these bikes were in production, although they quite likely made them as later replacements. The top gear ratio on your bike with a 42t is 4.64 to 1 and 4.75 for 43t. with a 20t standard engine sprocket which as the other respondants say will make no noticiable difference. Sorry if thisis more info than you need, but just make sure you order the correct parts for your bike.Another option would be to have the old drum re-toothed although you still have drum wear if you do this. Regards, Richard.

Previously Bryon Harvey wrote:

Dave what year is your ES2?

Brian, my apologies, with all the talk of 16H's and with me building an early Model 18 I've got them mixed up. My ES2 is 1949 and yes the one you have shown is correct. Held on by 3 dowls and 3 studs. I'll delete my comment so as not to confuse this post.

I'm new to plunger ES2's having owned mine for only three weeks, 1952 model, it has a new rear drum and sprocket but is bolted solid to the hub the rear wheel being removed complete with drum. I think I'm right in saying the drum with studs is for the rigid frame only. John

Hi Bryon / John

Yes the RGM sprocket is the correct type for a 1947-52 ES2 plunger frame, the rigid typeback wheel wasalsoused for the early swinging arm bikes ie. Dommi, Inter and ES2 until the introduction of the full width hubs which in the case of the ES2 was 1956. Regards, Richard.