[Dantheman]

Does anyone have any tips for trying to recover an old engine number stamped into a set of crankcases?

I have an early 1930's 4 valve Bullet (Model LF), a previous owner has excessively polished the crankcases and the engine number is no longer readable other than the first two letters. I have been looking particularly at a chemical etch, has anyone had much success with this before?

[Adrian II]

Know any good forensic scientists? UV light?

A.

[Boxerman]

We used ro use a crack locating spray where I worked, to locate finer - than - hairline cracks in hydraulic components.
It was a 3 part process, primer, spray & developer and would show up cracks not normally visible to the naked eye.
Not sure if this would work for your case, but it is all I can think of.

Frank

[Ove]

How about a high resolution digital camera, zoomed up on your screen? Some phone cameras are at high mPs  resolution. Play around with lighting angle?

[Kevin Mahoney]

you might want to try Baxter Cycle in Marne Iowa. They deal with this stuff everyday

[olhogrider]

We used ro use a crack locating spray where I worked, to locate finer - than - hairline cracks in hydraulic components.
It was a 3 part process, primer, spray & developer and would show up cracks not normally visible to the naked eye.
Not sure if this would work for your case, but it is all I can think of.

Frank

What you are describing is "dye penetrant". It is like magnaflux for non-ferrous metals. Aircraft maintenance supply houses carry it.

[Boxerman]

This looks like the stuff we used:
https://www.gas-uk.co.uk/crack-detection-spray-set.html

Frank

[grumbern]

It is possible to recover even sanded VIN's by scanning the material with x-ray. This will uncover the indents in the inner structure, even if the surface is smooth. I know this is used for crime investigation, but I don't know if this technology is somehow available to a "civilian" in an affordable manner. Just an idea. Chemicals won't work, as these tend to work their way regardless of the fine irregularities in material structure.
Andreas

[olhogrider]

It is possible to recover even sanded VIN's by scanning the material with x-ray. This will uncover the indents in the inner structure, even if the surface is smooth. I know this is used for crime investigation, but I don't know if this technology is somehow available to a "civilian" in an affordable manner. Just an idea. Chemicals won't work, as these tend to work their way regardless of the fine irregularities in material structure.
Andreas

Some aircraft, Beech 18 for example, require the wing to be x-rayed. If you can find an aircraft shop that performs those inspections they could probably do you. For a price. I doubt if any doctor's office would do it.

[Arizoni]

The equipment in a doctors office won't begin to penetrate metal if it has any thickness at all.

[Dantheman]

Interesting comments, certainly given a few more ideas, thanks 

[ERC]

Find an old registration where it came from. That should have a number. Unless it hasn't been registered in a lot of years.  ERC

[Dantheman]

Find an old registration where it came from. That should have a number. Unless it hasn't been registered in a lot of years.  ERC

The story goes that the bike has been untouched for 50+ years in Germany before making it to me, and unfortunately has no registration or supporting paperwork. Its still a project bike in its current state and missing a few pieces. 

[grumbern]

Did the engine come with a frame? Then the frame should give a clue to the engine number.

[Dantheman]

Did the engine come with a frame? Then the frame should give a clue to the engine number.

Yes, the engine is in a correct type 1934 frame which has been dated by the club (its about 90% of a bike), the engine is the correct 1934 type so stands a good chance they are paired from the factory, but it would just be nice to officially confirm this with the numbers through the owners club. The engine and frame number on these bikes would be unique to each other originally, as opposed to being identical like some other manufacturers.