Dating H.R.D. or Vincent motorcycles by frame & engine numbers.
HRD / Vincent motorcycles have always been a bit of a mystery to me. My main issue was that the models had more than one frame sections. Each one is numbered and you need to tie all of that into the records, along with the engine number.
In the UK, the registering authorities, accept the engine number and the number on the top section of the frame as the two pieces of information that is recorded on the log book.
I understand that other countries accept the engine number only.
There were so many model variations that it is probably best to begin with dating information for pre-war Vincent motorcycles by frame & engine numbers.
Before 1940, Vincent began to add a code system with prefix and suffix letters and numbers to distinguish one model from another. This method was similar to other manufacturers and the continued with the system after 1945.
Some Vincent motorcycles used JAP, Villiers and Rudge engines. This page is about being able to date Vincent motorcycles by frame & engine numbers, but it deals with Vincent engines. If you would like to lookup JAP engine numbers, go to this page. Or go to this page for Rudge engine numbers.
Prewar Vincent motorcycles by frame & engine numbers
A Vincent Pre-War Engine Number is usually in the form of 3 digits with one (or some) prefix letters. EG: V321
The engine prefix USUALLY denotes the model type.
V=Rapide
M=Meteor
C=Comet
TTC=Comet Special
TTR=TT Replica
TT=TT Machine
Vincent upper and rear frame sections were also numbered. They also had one (or some) prefix letters to denote the models, as stated above.
The upper frame member was usually 4 numbers and the model identification. EG: V3241
The upper frame member (UFM) has a number that is stamped on the steering head. The number in this position is the number used by the DVLA (UK) for all official records (MOT and V5c Registration documents). You use this number with the engine number to record the machine’s identity.
However, Vincent added a number to what they call the Rear Frame Member (RFM).
The Rear Frame Member (RFM) number is stamped on the left hand side near the wheel spindle. This may (or may not) match the number stamped on the Upper Frame Member.
The rear frame member was usually 4 numbers and the model identification. EG: DV3241
If the Rear Frame number doesn’t match the Upper Frame number, please don’t assume your bike is ‘non matching’. The only way of checking what numbers a machine left the factory with is by checking the Vincent Factory Records. So, the best policy is to join the Vincent Motorcycle Owner’s Club and the Registrar will cross-check your numbers with the records.
A fairly simple system was used for the frame member numbers. If the frame member had a D as a prefix, it was usually for the single cylinder machines. DV was usually for the Vincent Twins.
D=Single Cylinder Machine Frame Member (some Model J & Model P frames also used this prefix).
DV=Twin Cylinder Machine Frame Member (Rapide — most but not all).
Caution: As is the case with almost all vintage motorcycle manufacturers, there are exceptions to the rules. This information is provided as a guide and it’s always best to consult the Registrar at the Vincent Owner’s Club. The Registrar can cross-check your numbers with the Factory Records.
Post-war Vincent motorcycles by frame & engine numbers
After 1945, Vincent HRD continued with the prefix code system, but made it considerably more detailed. The letters and numbers on the engine offered a great deal of information. To see the number, look on the left side of the engine crank case. It’s just under the front cylinder barrel.
A Post-War engine number is usually in the form of F10AB/1/5036
This suggests that the engine is A Four-stroke, 1000cc, Aluminium cased “Bicycle” engine. It was supplied for either a Series B or C Rapide and had a unique sequential number of 5036.
The following are the de-codes for the post-war Vincent motorcycle engine numbers.
Engine Type: F=Four stroke. T=Two stroke.
Cubic Capacity: 10=1000cc. 5=500cc. 07=70cc. 05=50cc (eg. Firefly Cyclemotor).
Engine Material: A=Aluminium. M=Magnesium Alloy.
Engine Purpose: B=Bicycle. M=Marine. U=Utility.
Twin Models (between the obliques): /1/=Series ‘B’ or ‘C’ Rapide. /1A/=non-standard model (including White Shadow). /1B/=Series ‘B’ or ‘C’ Black Shadow. /1C/=Series ‘B’ or ‘C’ Black Lightning. /2/=Series ‘D’ Rapide or Black Knight. /2B/=Series ‘D’ Black Shadow or Black Prince.
Single Models (between the obliques): /2/=Series ‘B’ Meteor. /2A/=Series ‘C’ Comet. /2B/=Series ‘B’ or ‘C’ Grey Flash. /3A/=Series ‘D’ Comet or Victor. /4/ and /5/ usually indicates that the crankcases are reproduction.
An Upper Frame Member Number is usually in the form of RC/1/1324/B/D
The Upper Frame Member (UFM) number is stamped on the steering head. The Upper Frame Member (UFM) number can be broken down into its prefix, serial number and sometimes a suffix.
In the case of the example ( RC/1/1324/B/D ), the number is for a “C” series single cylinder Comet motorcycle (RC/1/). The suffix letters are as below.
Vincent motorcycle Frame Number Prefix
R=Series ‘B’ Twin
R/1/=Series ‘B’ Meteor
RC=Series ‘C’ Twin
RC/1/=Series ‘C’ Comet
RC/1A/=Series ‘C’ Grey Flash
RD=Series ‘D’ Twin
RD/1/=Series ‘D’ Single
Frame Number Suffix
B=Black Shadow
/A=Metric taper wheel bearings (front wheel only)
/B=Metric taper wheel bearings (rear wheel only)
/C=Metric taper wheel bearings (both wheels)
/D=Ball wheel bearings with circlip
/E=Ball wheel bearings with lock rings
/F=Series ‘D’ Black Knight
B/F=Series ‘D’ Black Prince
Be careful. Do not confuse /B as a Black Shadow as it refers to wheel bearings. You can get B/B which is Black Shadow with metric bearings in the rear wheel only. Dating Vincent motorcycles by frame & engine numbers needs to be done with care.
Also, if the Upper Frame number doesn’t match your expectations, please don’t assume your bike is ‘non matching’. The only way of checking what numbers a machine left the factory with is by checking the Vincent Factory Records.
The Rear Frame Member (RFM) number is stamped on the left hand side near the wheel spindle. This may (or may not) match the number stamped on the Upper Frame Member.
The rear frame member number was usually 4 numbers with some prefixes. It was usually in the form of RC/1/1324
If the Rear Frame number doesn’t match the Upper Frame number, please don’t assume your bike is ‘non matching’. The only way of checking what numbers a machine left the factory with is by checking the Vincent Factory Records. So, the best policy is to join the Vincent Motorcycle Owner’s Club and the Registrar will cross-check your numbers with the records.
Other numbers stamped into the engine crank cases
When dating H.R.D. or Vincent motorcycles by frame & engine numbers, it is possible to be a little confused by other numbers stamped into the engine.
I have been given crankcase “mating numbers” as engine numbers in the past. They are numbers that relate to the engine, but they don’t help with identification of the year, cc and model / variation at all.
Mating numbers are a pair of stamped numbers that (usually) match. They are located on the crank cases. They are in any combination of letters and numbers. The purpose of the letters and numbers is to show that the two crank case halves are a matching pair from when they left the factory. The halves are machined so that they mate to each other as a pair.
On the twin cylinder machines they are usually seen between the cylinders, and on both halves.
On the single cylinder Vincents, the mating numbers are usually stamped behind the cylinder.
Look for a pair / set of numbers that match on both cases. If they match, check them carefully to make sure that the fonts are the same. If the fonts are different, take more time to look at the engine as a whole, as it is likely that one of the pair of numbers has been altered. If the sets of numbers are different on each engine case, then you have a mis-matched pair of cases. It’s not the end of the world, but it does mean that you need to consider that the engine may need to be taken apart and some time will have to be spent matching the cases up.
Other numbers stamped into the side of the crank case above, or just below, the engine number
If you see another number stamped into the side of the Vincent engine, it is likely to begin with EV or RS.
These numbers refer to engines that were built by either Fritz Egli, or Roger Slater. Fritz Egli designed his own competitive motorcycle built around a performance Vincent Twin engine. He licenced the design to Roger Slater in the UK.
Read all about Egli-Vincent motorcycles on this page.
All of this information is provided as a guide. When dating H.R.D. or Vincent motorcycles by frame & engine numbers, it is best to begin with the engine number, together with the two frame member numbers. Then contact the VOC to make sure that the motorcycle conforms to the factory records.
