Rob's WD16H and Big4 Forum

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Rob's WD16H and Big4 Forum
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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.