Where can I find my bike frame and engine number?

Buying a classic motorcycle can open up a whole new world of biking – machines with none of the electronics or fancy fuel injection of modern bikes, and with the potential for many happy evenings of tinkering in the garage. But making sure you’re getting one with that is what it claims to be can be harder, thanks to the fact that the frame and engine numbers can be in some pretty unexpected locations.

On modern machines it’s usually a simple case of checking the headstock and the rear of the engine, so this guide will show the exact position of most bikes that now have ‘classic’ status, or in the case of mopeds, scooters, flat twins etc, an approximate position…

Depending on the bike, locations to look for the numbers are:

• Headstock
• Nearside top of crankcase below barrel(s)
• Top of crankcase behind barrel(s)
• Cross member below tank/saddle join
• Front of crankcase
• Approx position only
• Top nearside of crankcase behind barrel
• Nearside frame down-tube below headstock
• Offside top of crankcase below barrel(s)
• Cylinder head
• Offside rear fork leg in front of wheel spindle
• Approx position
• Front nearside of crankcase
• Front nearside frame down-tube on lug
• Recess under nearside crankcase
• Offside radiator frame loop
• Reynolds fork approx position
• Under offside of crankcase
• Under and forward of nearside crankcase
• Nearside rear fork assembly near wheel spindle
• Nearside down tube lug
• Offside frame down-tube below head stock
• Offside crankcase cover

Where to find your motorbike frame or engine number

Using the image above and the following key, you should be able to look in the correct location for almost any model of classic motorcycle. The numbers correspond to the picture above, while the codes mean the following:

As an example, 1FS-2ES shows that the frame number is stamped into the frame (FS) at position 1, and that the engine number is stamped into the crankcase (ES) on the nearside barrel at position 2. You will find variations in locations for some brands – BSA for instance has three possible frame number locations and one for the engine. The numbers represent the area to look – number 24 for instance is where the frame meets the top tube.

This is intended to be a guide for those who aren’t experts in each marque, but we do welcome any updates or additions – please drop us an email at enquiries@bikesocial.co.uk

Motorcycle manufacturer’s frame/engine number locations