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Instruction sheets, quick tips or technical articles. You’ll find it all here. All information on these pages is accurate to the best of our knowledge. If however you do find something incorrect please let us know!

A number of our products come with their own instruction sheet. If you have misplaced yours, or would like to take a look before buying, you can find them all here!

On this page you will find a selection of technical hints and tips that we think you may find useful but don't justify a page of their own.

Given that most manufacturers stopped using girder forks over 70 years ago, it is not at all uncommon to find forks badly worn or damaged. This page shows how a few of the common issues can be repaired.

Engine Calculators

Engine displacement can be calculated from the bore and stroke. Once you have the displacement you are one measurement away from calculating compression ratio. This page shows you how to do all of this.

Trigonometry can be used to convert crank rotation to piston drop. If you have one of these figures but you need the other for any reason, this page will show you how to get the information you need.

Some relatively simple calculations can be used to convert road speed to engine speed or vice versa. This can come in handy when selecting gearing so we'll show you how to do it on this page.


If you aren’t sure what thread is used where on your British bike, have a look at this page.

Most American and some later British bikes will use Unified Thread Series. Have a look here to help identify them.


Pre-war Norton engine and frame numbers aren’t consecutive and don’t match. The engine numbers can however be used to give an idea of the year of manufacture. Here is what you need to know.

Post-war Nortons can be identified by the prefix on the engine and frame numbers. Here is a list of what they mean.

A table showing data including valve and ignition timing for Norton singles from 1928-1955.

If you are trying to get the best out of your engine it is one area that significant gains can be found. Take a look to see what your options are.

The tunnel in the SOHC camboxes are often broken on a Norton, allowing even more oil to leak out past the seals. We had to repair the one on my Norton International so here’s how you can do it.  

A modified 16H piston can be fitted to an ES2 to raise the compression. Here is what needs doing.


From the first MOV to the last Thruxton the M series Velocettes all used the same basic design for their cams. Look here for the timing figures for each cam along with clearances and a note on what they were originally fitted to.

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