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Rob's WD16H and Big4 Forum

Dutch army, Johan Herman Fuhler, somewhere between 1945 and 1950

Rob's WD16H and Big4 Forum
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Help Identify Big 4

I recently inherited what ive identified as a Big 4. It belonged to my Nannu who shipped the motorcycle in pieces from Malta to NY about 50yrs ago and reassembled it. I am kind of confused by the chassis number as it looks more like a 16H chassis number so I was hoping I could get some help from you folks. The chassis number is W35776 and engine number S3858. I have no idea what year the bike is and I have no paperwork on it. I was told as a child that it was a military bike used in South Africa. The original sidecar didnt survive the trip to the US so my Nannu replaced it with a Watsonian . Its non driven and theres no evidence that it was ever different. I do have several pics of the motorcycle that might help if necessary. I appreciate any help as I have no starting point to even try to get the proper paperwork so that the motorcycle can see the road again.

Re: Help Identify Big 4

James, I think that you've done the basics when it comes to identifying what you have. Any Norton frame with an original 'W' prefix is from a 500cc WD16H..and any engine with a number beginning 'S' is from a 633cc sidecar wheel drive Big 4.

The Big 4 frame is quite different and allows for the fitment of a rear wheel which could also drive the sidecar wheel. Yours will not have this possibility.

W35776 was part of contract C7353 and would date from early 1941. It would originally have borne the WD serial number C4395802.

 photo A1941C4395610W35584C7353_zps6cb6a429.gif

Engine number S3858 was part of Big 4 contract C11297 and would have been numbered C4591768 - it dates from the end of 1941.

 photo A1941C4592115C11297FreeFrenchLeBig_zpsb6249f30.jpg

The fundamental difference between the two engines is that the 16H followed what is generally referred to as the 1937 pattern and the WD Big 4 used the 1938 type with enclosed valves.

They have quite a different appearance but the combination is not that uncommon and to be honest is probably what anyone with access to the parts would have fitted to their 16H for sidecar use given the opportunity...the extra torque of the Big 4 would certainly come in handy.

There is no real evidence that British or Commonwealth armies ever fitted Big 4 engines to 16H chassis. They had enough spare 16H engines and wouldn't have wanted the spare parts complication.

If you rebuild it in military trim, it would not look unlike a civilian impressed 1938 model...although rivet-counters can identify the WD frame from its geometry. If building a 'civilian' trim Norton then it really has to be silver with red / black coachlining....

Photos would certainly help identify if you have a rolling chassis with a full complement of original WD fittings or if post-war use has resulted in further modifications.

Does your engine have any additional stampings ? I'd certainly be keen to see a close up photo for my 'Ministry Inspector' database.

Re: Help Identify Big 4

Thank You very much for your help Rik,

Hopefully these pics will show and you will be able to see why I originally thought I was dealing with a Big 4. I dont plan on restoring the motorcycle to original trim but will be preserving it as my Nannu built and rode it many years ago.

I have several boxes of spares that I need to catalogue and the engine may be frozen so I have quite a bit of work ahead of me.


Re: Help Identify Big 4

The Big 4 front mudguard does change the look but apart from that and the engine, it seems to be all 16H to me. Wheel rims could be 18" but these were also fitted to some (RAF, I believe) 16H sidecar outfits.

You've got a pretty complete machine there, leaving you the choice of a full restoration or a 'tidy-up' and recommissioning.

Feel free to post pictures of the parts and I'll do my best to help with identification.

The Big 4 engines are harder to find parts for than the 16H (far fewer made and a shorter period in service).

Re: Help Identify Big 4

Thank You again Rik,

The Big 4 front mud guard and 4.00 18 tires had me fooled as a novice. I'm hoping that I can get away with just cleaning it up, new tires, and fresh fluids. First I need to figure out why the kickstart lever will not return.

I will be sure to post pics of the spares as I seperate them and i'm sure I will have several more questions needing answer.


Re: Help Identify Big 4

Hello James,

May I add your MC particulars to the website?

I would be pleased if you could send pictures of both frame and engine numbers.



Please use the e-mail adress given.

Re: Help Identify Big 4

Hi Rob,

Yes, you can definitely add the particulars to the website.

I will need to clean the frame a bit to make the frame number a bit easier to read but I will get some pics over to you as soon as I get this done.


Re: Help Identify Big 4

Perhaps a broken return spring? Mine came with two spare springs. Apparently that was about the only thing that ever went wrong with it.