16H/Big4 engines

.... on earth scrap it? I'm sure it has the makings of a decent bike with a bit of work. I'll give him £100 for it......

The major engine components are interchangeable and can be made to work properly. Are you sure it has not just wet sumped? Otherwise you will be looking for all the usual causes of smoking such as worn bore, stuck rings, oil pump, breathing etc etc. Another factor: according to Roy Bacon Big 4 was 120mm stroke until 1948 when it changed to 113mm. You could check the crankcase for date & model codes. Year codes started in 1946 with A, Big 4 is model code 7. Model codes 6 or 9 (for 19R & 19S) would also have 82 x 113 dimensions but I am less sure if the SV top end can be made to work with OHV crank cases.

Ian McD

At the suggestion of Richard Salt I recently joined the NOC. The bike under discussion belongs to me. I purchased the 1934 Norton thinking it was a Big 4 but it seems that it is a 16H. The main problem with the motor is that there is a very high sump pressure and the scavenger pump was not emptying the sump quick enough, from time to time the sump would fill with oil and then start to smoke badly and push oil out of the sump breather. The oil returning to the oil tank seems to have lots of little bubbles in and looks like foam, oil flow was also sporadic as it should be. I have just disassembled the motor and have found the Oil Ring was broken, top two ring gap is 45 Thou.  Oil pump look OK but I do not know how to check if it is 100%. There was NO blockages in the oil feeds or oil pickup. Any pointers would be appreciated.

Regards 

Tim

It may be a good idea to post some photos of the engine to be certain what you have.  The Big 4 from the earliest days until 1948 was 82 x 120mm (633cc) and the 16H was always 79x100 (490cc)

The vintage OHV Model 19 was 79x120 (596cc) but it changed in 1933 to 82 x 113mm (596cc)

For 1948; the chimney pot Big 4 adopted the pre-war Model 19 bore x stroke and became 82x113.

If the stampings are original, your cases either have to be converted from OHV or the engine is post-1948.

I can't think of any differences in the scavenging systems, but if it really is wet-sumping in use and the fibre washer is present on the oil pump then perhaps a new Andover Norton pump might be a good idea ? They are steel-bodied as per the twins and really do make a difference.

In the Edgar Frank's book he says that the OHV and SV cases start off the same but they are so differently machined that it is not practical to change one for the other. So it's not likely to have OHV cases.

According to "Norton" by P L Garratt the ring gaps on a 16H should be 0.010" for both compression and oil rings. 45 thou seems excessive and might indicate that a rebore is required. Have you checked piston to bore clearance with a feeler gauge?

As Richard has suggested check the fibre washer on the pump outlet spigot. The distance from pump outlet spigot to the timing cover face can vary from engine to engine, so the thickness of the fibre washer has to be correct to ensure a seal at that point. Too thin and it won't seal, too thick and the timing case can be stressed when tightening the screws. The OHV maintenance manual calls for a gap of 1/32" between the inner and outer timing cases before the screws are tightened.

Original oil pump bodies have been known to distort/bow and so can leak from the crankcase to oil pump face, hence Richard's suggestion of a new steel bodied pump (expensive though). It should be possible to flatten the pump mating face using a glass plate and grinding paste, but make sure all the paste is cleaned off before refitting. A new pump would also eliminate inefficient pumping caused by internal wear between the gears and pump side cases.

Ian McD

It's been done the other way, David...This is a WD16H bottom end...OHV top is earlier though and it's not a good looking conversion.

Some people will do almost anything to an engine... Allen Millyard comes to mind!

We shouldn't lose sight of the fact that Tim's bike is supposed to be a 1934 model. Some pictures of the complete bike, as well as the engine, would be good.

And have Tim and Richard checked the frame number, assuming that one is visible?

Whatever you have it should be worth perservering with. Decades ago I had a post-war Big 4 (which I sold to help finance a '71 Fastback), and it was a charming bike.

Hi Chaps,

The Engine number  is 58225

The frame number is E6293

I will post some pictures of the 1934 Norton. I would like to know if it is a Big 4 or 16H.

I have attached a couple of pictures of the inside of the engine of my 1934 Norton as suggested.

Hope this helps to find the problems I am having.

I have posted a Picture of the piston. I am going to replace the piston , rings and do a rebore.

Engine side covers look like early 30's, and engine number also. Frame number is odd because by letter E they would have had telescopic forks. Tool box is post war  so my guess is that frame has presumably been replaced at some time. Girder forks are nice (I think...). Just enjoy it. It looks good and it is a Norton  so what's not to like?

As someone who has no idea what it should look like, to me it looks a tremendous old brit bike.

is it a twin plug head? Or is that where a spare is carried? 

There should be a blanking  plug to allow piston drop to be easily measured for timing. A spare plug does the same job.

That's definitely a more-or-less contemporary engine and it looks to be all original side-valve to me. You have a January 1935 engine build date stamped there. It would be worth asking the Club Records Officer what the engine number relates to. It wouldn't be the first example that I've seen with the wrong bore x stroke on.

The frame, with vertically-mounted saddle springs has a  long down tube and is not WD so is pre-1937...I think that the 'E' number is a casting number. Have you looked at the front left-hand fuel tank mount ?

***Thanks, David Cooper...Have now edited my post to state 'vertically' and to correct the year....a confused typo last night as that's what it has. The civilian frame saddle spring lugs went horizontal for 1937 as part of the change to a lower seating position.***

The photo shows upright saddle spring supports. But I think the sideways ones might only have been used from 1936 to 38, so if that's so it could be earlier.  Someone must know, but I can't find it written down.  It has a prewar oil tank.

They were very similar engines the first 16h, and the last? (The photo shows one from the year 1947 and is similar to Tim's). Greetings to all.

Hi Richard Payne,

I have posted a photo on the Engine number and the Frame number. 

How do I ask the Club Records Officer for information on my Norton.

What should I look for on the front left fuel tank mount, this is where the frame number is located but is there any thing else I should be looking for.  

Regards 

Tim

Hi Again Chaps.

As I have no way of checking the efficienty of the oil pump I am thinking of a NEW oil pump.

 Ian MacDougall  Attached is the Andover Norton oil pump ( NM15521 Oil Pump Assembly Single A2/128 )  is this Andover Norton pump the correct one, It might be a good investment for me as I intend keeping the Big 4 for many years. Will this oil pump bolt straight on.

... and well worth getting back on the road regardless of the details.

Hi Tim 

What you have photographed is not the frame number. 

The frame number is located on the front casting below the front petrol tank mount. 

Have a  look and see what number is stamped there. Could be partially covered with paint. 

Hi Ian,

Thanks, you are correct, I fount a number exactly where you said, the number is 54022. I have attached a photo, you can make  just make out the number. Hopefully this will help to identify my Big 4/16H.  I have also requested/paid to get more info on my Norton from NOC.  Thank you for the assistance. 

Don't forget to let us know the outcome please Tim. Your stampings look good and clear, and original to me. 

Your engine can't be any type of conventional Big 4 as with this type of engine, they were all 82 x 120mm. I suspect that an apprentice got carried away after stamping some Model 19 engines and never owned up to the error.

This is a wartime sidecar wheel drive Big 4 (1938 pattern) crankcase with the correct 'S' prefix for that model...but stamped 79x100...It clearly happened.

If you look closely at the cylinder flange, above the engine number, you may be able to see a number stamped there too. This was a standard feature  and would show if your 100mm stroke cylinder started life on those cases.

Thanks Richard,

I will let you know about the Factory record check. Do you know if the NOC Recodrs Officer is currently working.

Regards

Tim

He's a volunteer, Tim..I've been in touch with him fairly recently so I hope he's active and well.

Tim, to the best of my knowledge that is the correct pump for all SV & OHV singles.

Will it bolt straight on? I bought a new pump for my 19S last year, looks very similar to that one but was NOT supplied by Andover. It was a very tight fit over the studs. It think it could have been "persuaded" to go on but I was concerned that it would have been very difficult to remove. The original pump slid on & off easily. The holes were the correct diameter but it seemed that the spacing was very slightly out. With serious misgivings (invalidation of warranty) I eventually enlarged the holes by 0.2mm which solved the problem. Then I discovered that the outer timing case was not closing properly due to contact with one corner of the pump. A little filing at that corner of the brass end plate allowed the cover to close properly. I didn't complain to the supplier, I know I should have.

Ian McD

I understand the new pumps are iron, and the old ones for singles were white metal. The way Nortons made their parts department's staff lives difficult with minor design changes, I'm not sure modern suppliers are entirely to blame.

The hole spacing was so nearly right. Unlikely that a minor design change would move the position of a stud by 10 thou or so. More likely to be a tolerance issue, either when Norton inserted the studs in the cases or when the holes were bored in the new pump body. If the factory drawings are no longer available then today's manufacturers of spare parts can only make an educated guess at the tolerances to which Bracebridge Street were working. As for the timing case to pump interference, I may be partially responsible as I fitted a paper gasket between the pump and crankcase. There was no gasket behind my original pump. The change from white metal to iron (or possibly cast steel?) should be a good move. A straight edge on my old pump body showed that it was bowed, hopefully that will not happen with the new pump.

Ian McD

Thank you Ian MacDougle and David Cooper for the information on the new oil pump. I have ordered the new oil pump from Andover Norton. It might take some time to get to South Africa as we are going into total Lock Down.

Regards

Tim Hammerich