Rob's WD16H and Big4 Forum

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Rob's WD16H and Big4 Forum
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Big 4 and 16H Cruising speed

I have a couple of old BSA's (A7 and B31) and know very well how these overhead valve engines perform in modern traffic but I have no idea how a side valve would cope.
I am contemplating adding a Big 4 or a 16H to my motley collection with a view to riding not showing but I seem unable to find any useful performance reports. I know SV's are sedate and that is their charm but would either of these bikes be able to cruise all day at say 55 mph or is 45-50 mph a more realistic speed.
I think 55 mph on A and B roads would keep up with most traffic whereas the lower range would mean being constantly overtaken and probably carved up!!
I love the idea of an old SV, I just want to know if I'm going to be content with it's performance before I go ahead.
Any comments on this would be most welcome.

Re: Big 4 and 16H Cruising speed

There may be a difference between what the bikes are capable of doing and what the rider can put up with...I assume that as you're posting on the WD forum, you're talking about rigid / girders ? The WD Big 4 was only available as a sidecar-wheel drive combination which is not to say that there have never been 633cc solos based on the WD16H rolling chassis.

Period road tests refer to regular stints at 55mph and bursts up to 16H with a 19t engine sprocket is certainly sweetest at around 45mph. I'm quite happy taking it up to around 55mph for a mile or two where needed and it will go faster but this is not really what the bikes are about. I can't imagine what it feels like to 'cruise' all day at be honest, that's hard riding on one of these.

Above 50mph or so they feel quite busy and safe progress is related to road surface and traffic conflict situations. Unless you're building a special, you have an eighty-five year old drum brake design and sixty miles per hour is sixty per, whatever you're and tractors don't appreciate this and will happily pull out in front of these odd, low, slow-looking bikes. There is no way that I'll hold 60mph riding past a car at a sideroad or even on a driveway. It simply takes too long to stop.

However, it's not all're not on a 1950s lightweight or even a 175cc Bantam. The 16H accelerates smartly and corners well. I'm quite happy on pretty well any single carriageway road but fast dual carriageways can be intimidating, as much of the traffic will be at motorway-plus speeds. On an ordinary road, you won't hold up normal traffic - of course, there'll still be the Audis howling down on you but that's as true at 80mph.

If your BSAs are plungers then you'll be used to watching road surfaces but a rigid is nothing like a duplex A10 with decent forks and shocks. A dropped manhole or a horizontal ridge can send you airborne and landings are less predictable than with damping.

If you're looking for an adrenaline rush then a side-valve is not the bike to choose but you'll still find yourself overtaking the odd modern Harley-Davidson :-)

Re: Big 4 and 16H Cruising speed

Hello Ric,
Thanks for your response. I didn't realise the significance of the WD site, I was probably thinking more of civilian models. I'm sure the girder fork and rigid rear end models are rather unforgiving where cushioning is concerned!!
I am used to riding plungers I find them more than adequate for my needs.
I'm not after an adrenalin rush by any means but reasonable progress is important. I mostly ride around the Cotswolds and sometimes go over to Wales and tend to ride stints of half an hour or so at 50 - 55 mph.
I may hope to do complete one or two rides a year of 100 to 150 miles in a day but that is rare. Usually 50 - 60 miles is the norm. I'm used to drum brakes and find them quite effective when well set up.

Most people think of speed and performance when they refer to Norton's but I never was one of those, I like the charm and nostalgia of the older models and not many people these days have much experience of SV's.

So I will probably look for a late Big 4 with hopefully tele forks and plunger rear suspension. I think from what you have told me I will not be disappointed.
Sorry for talking civilian bikes on this WD forum, I did not realise my error.
Thanks again

Re: Big 4 and 16H Cruising speed

Hello Wayne,

As the military bike was really a civilian version of 1935 its not so strange to look at the site.
Most of the technology is the same.

Wrt speed I can only concur with Rik that it can go fast but its not comfortable on longer runs. Apart from brakes and road "holding" the vibrations will be sufficient to wear your teeth.

They are wonderful MC's to ride but I may be predjudiced.
I also like to go "slow"as it gives you the time to look around and not ending in a ditch to quickly.

I can imagine a 1947 or later 16H or B4 would be a little more suited for you.
B4's were more used for sidecar work but can certainly be ridden solo very well (even the military one!)



Re: Big 4 and 16H Cruising speed

Interesting that you've put a 19 on Rik. Do you think it would pull a 20?
I find the 16h far lower geared than a an M21. My M21 is perfectly happy at 55. Oddly though the 16H is very happy to putt around at 35 or so it's peak torque appears to be further up the rev range almost at the point where it starts to vibrate. On a standard 18 the best compromise is for me is around 40. I know the top speed will come down with a 20 , I'm just interested in a touch higher cruising speed. Just been to Holland where I entered a clogmaking festival at Enter.

Re: Big 4 and 16H Cruising speed


my experience is that a 20 teeth sprocket works well. ( if your engine is in good order ) I found that at 55 Miles / 90 km/h the engine runs perfectly smooth. You even have the impression that she will make the 100km/h without effort - but this is not true.
You surely do not have as much punch to go up hills in 4th but you can live with it. I have both the 19 and 20 teeth but did not return to the smaller sprocket.Especially in the lower gears the 20 makes cruising even more relaxed ...if ever this is possible.


Re: Big 4 and 16H Cruising speed

Jeremy, I think that the 16H would probably pull a 20t in most circumstances, especially as I'm only 10 1/2 stone and don't have pillion facilities. The WD16H will always be slightly lower-geared than pre-war civilian as it has a 43t rather than 42t rear sprocket.

I'm not a great fan of over-geared bikes - nothing worse than the feel of it tailing off in top into a headwind and if I see a green lane, I like to ride up it (even though I'm paranoid about the 8" Difusa glass !)For me personally, a 19t is fine.

Someone once used the word 'cadence' when referring to an old single cylinder bike and for me that sums it up perfectly. At 45mph with the 19t, the revs aren't too high, the thing just booms along and the girders are in perfect harmony with just a hint of side-damping. 10mph faster means a harsher feeling engine and suspension on most road surfaces (maybe not in Germany, Heiko but in Belgium, believe me roads become exponentially bad above 55mph on a rigid !)

I wouldn't discourage anyone from running a 20t on a well set up 16H, especially if they have a 43t rear but I haven't felt the need to change. If I need to get somewhere quickly, I'll take my 'modern' bike (a forty year old Commando).

Re: Big 4 and 16H Cruising speed

I also run a 20 T sprocket, I have found it works well for me. Of course, I was used to an 18T which was great on a steep hill, but really lacked in traffic. The bike pulls very well in all gears. I find 1st feels more like 1st than a bull low. A steep long running grade however will tax 4th pretty hard, with a need to downshift to 3rd. The bike, as most of them do, loves 45, but sustains 50 with no effort and will do 55 to 60 in short bursts. Of course the bike is tip top mechanically, these figures would drop down with a bike in lesser condition I suppose.

Re: Big 4 and 16H Cruising speed

The overall ratio on prewar civilian bikes was (brake drum/gearbox x clutch / engine) = 42/19 x 42/19 = 4.89. For WD is was 43/19 x 42/18 = 5.28.
So the civilian bikes had about 8% higher gearing. So same revs at 50mph for a WD bikes gives 54mph for civilian.
It doesn't sound a huge amount! But I don't see any virtue in flogging an engine up hills in top gear when I have a nice Norton gearbox to play with.

Re: Big 4 and 16H Cruising speed

Havn't been on the site for a while, good to be back and have a look around and see the changes.
Really interesting conversation regarding speeds of the big four and 16H.
I own a war era (1942ish) 16H and a 1950 Big 4. I do have war era Big 4, but it's not a runner.
My 16H goes quite well, I've had it running now for about 5 years. Engine wise it had a new piston, valves & guides when I built it. New main bearings, but runs the same big end as it had when I put all the bits together. I did split the crank and cleaned the bearing, so even though it had seen use, I put the engine back together all clean and with nice fresh lube through the big end.
I have played with the gearing over time and run a 43 tooth rear drum/sprocket, 19 tooth gearbox sprocket, 42 tooth clutch and 21 tooth crank sprocket.
Bike runs quite well, sits on 50mph easily and have been clocked at 64mph down a long hill with tailwind. I was going to say laying flat on the tank, but in reality at that speed I was mostly up in the air off the seat hanging onto the bars for grim life.
As others have said, anything over 55mph especially on Australian roads and you are taking your life in your own hands. The bike is absolute fun to ride and it has probably the biggest grin factor of all my bikes, I love riding it. The 21 tooth sprocket means it slows on hills and you need to change down to third, which is ok except if I don't make a posative change then sometimes it jumps out of third which it never does on the change up from 2nd to 3rd. To then go from third to second is a giant drop which means if the hill is that steep you won't get back into third, the ratio gap is just too great, you stay in 2nd and take it easy till the top of the hill. Having said that the hill has to be quite steep to go back to 2nd. Third with a bit of retard will usually do the trick. There is an art here in riding these things to be learned and patience is high on the list of necessity. Revs don't really worry these things because the lack of efficient breathing on the sidevalve engine is really the limiting factor rather than piston speed etc etc. You can't do valve damage to them because the valves are nowhere near each other and won't get tangled nor are they anywhere near the piston, so no worries there.

I have not ridden a war era Big 4, but my 1950 Big 4 is different again. I also own a 1956ish Model 19 and a 1950 ES2. The ES2 and the 16H share similar engine characteristcs in some ways while the long stroke larger bore Big 4 and Model 19 share some engine characteristics, I'm sure the war era big 4 would be similar to the 1950 Big 4.

The major difference between the Big4's and the 16H is the Big 4's have bigger fly wheels and you can feel it. Couple that with the bore & stroke to give a bit more oomph and they are quite different to ride. My big 4 has the same gearing as my 16H. I have had taller gearing on the Model 19, but have brought it back to the same 21 tooth engine sprocket.

The good thing about the big 4, and I can only speak for my 1950 model, is that it holds much better up hills. It rolls at them and rolls up them. This means you hold your speed much better, so over a distance they are quicker, they pull harder and come out of corners quicker. I look forward to the day I get my war era big 4 engine going, for a start it will be in a 16H frame and will be a solo.

My 16H is rigid frame, girder forks. The 1950 ES2 is plunger frame tele forks. The Big 4 is rigid frame tele forks and the Model 19 is swing arm frame tele forks.

The 16H will do 50 -55mph and can do 60mph, but as others have already said, this is way out on the limit of what the frame and forks and your body can handle. If the roads are anything but billiard table smooth you need to hang on and watch and read the road and be really careful of bumps and potholes, especially cornering because the bike will jump sideways and throw you off. My big 4 rigid with teles is a more forgiving in the front end but the rear will still step out and the if the bumps catch you unawares they belt straight up your spine. The Big 4 will cruise up around 60mph and I've been clocked at 74mph on the flats. The ES2 naturally runs better with the OHV motor and is much better with the limited suspension of the plunger. I can imagine what a revelation plunger rear suspension was back in the day. A much more comfortable bike to ride. naturally the Model 19 with swing arm rear was a huge leap into the future and that bike gets along easily at 70 - 75mph. Once again the big flywheels and the extra bore & stroke same as the big 4 pull up hills and tend to level out the roads in comparison to the 500cc ES2. Norton should have put a lot more into their Model 19 and Big 4 motors, they were much better.

Riding the 16H, it's how you go about it. Ride it with the right approach and its heaps of fun, for me the grin factor is the best.