Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Engine number query

On my 55 Thunderbird there is another number below the engine number:
6T (spoke sign) 62840R
C1747
Can anyone tell me what the extra number means
Thanking all in advance.

The cartwheel symbol is to indicate ramp cams. From your earlier post, your bike must be a factory special, as all standard '55 bikes had swinging arm frames, the "R" at the end of the engine number would appear to confirm that. I am guessing that the second number may be a batch identification, possibly done for police/army or a large dealer in Oz? The VMCC or TOMCC have copies of the dispatch (despatch) records which may give a clue.

Ramp cams were standard on pre-unit Thunderbirds beginning with engine number 37560. Some 5T and T100 models also had them.

C at or near the engine number can mean it left the factory in sidecar spec.

Here's the Service Bulletin for info.

Thanks for the info, as I said in previous posts, my bike is a rigid frame & has always had a sidecar fitted, so that could explain the (C) but I can't figure on the other number unless it is the 1747 th sidecar spec!!