Frame number on 16H

Previously norman_hawkins wrote:

Hi

Hoping to get a lovely 16H back on the road but need a date letter. Eventually I have found the frame number in its proper place on the left fuel tank lug, but it is very faint. I have photographed it, magnified it rubbed some chalk on it, but it is very difficult to get the numbers clear and easy to read. Any tips? Should I remove some paint, scrap it, don't scrap it, use thinners?.... What should I do?

I have found only one way that works. Mask off the area and sandblast down to bare metal. Then, with a magnifying glass, you can see any faint trace of a number or letter.

You should be able to put paint stripper on the area, then rub it with some fine emery paper. This usually leaves a bit of paint in the numbers that helps to read it. Make sure you've stripped back enough that there isn't another digit. I did that with a frame once, I was sorting out dating letters etc only to find another digit I hadn't uncovered

Don't use a grinder or sander, you end up damaging the numbers and make them look suspiciouslike some one has altered them. I met a bloke with alovely collection of Norton's. He'd used a sander on every frame to get the paint off, cutting much too far into the metal and ruining them. If the bike is apart, then you can use fine beads and blast it, but you'd have to be careful blasting on a complete bike. The grit goes places you really don't want it no matter how well you mask off.

To my mind, it depends on the paint finish. This is however too important a matter to make a mess of it !

I do think though that you'll need to take it back to bare metal. If it's a home-done paint job then a thinners rag might be enough. I'd then use a brass wire brush which won't remove any of the frame material. It's important with these investigations not to remove the casting and fettling marks as if they're gone, even original numbers can look dodgy.

If the frame has been powder-coated then it has probably been heavily bead-blasted and acetone is about the only solvent that will soften it, again followed by the brass wire brush.

Norman, roughly what year is it ? Is it ex-WD or civilian ? A photo would be handy.

I find old-fashioned suede brushes handy...Don't risk bringing them back indoors afterwards though....

I found this.No guarantees!There are two techniques commonly used. â? Destructive. â? Non destructive. Non destructive:The non-destructive has you incrementally polish the area with multiple rubbings of the area with 1200 grit sandpaper, inspecting and photographing the area between polishings. Sometimes, the use of a photo editing software package you can increase the contrast sufficiently to perceive the serial number.Another amateur technique involves cleaning and polishing the area as above. Then try a 5% solution of citric acid in water, saturate the number area and apply heat from an oxy/acet torch. If that doesn't provide a readable number, I have also heard that Murine eye wash and a black light may also do the trick.Destructive:The second technique is the destructive method. When the metal was originally stamped the metal grains are more densely packed than the surrounding area, the use of an etchant will eat the softer surrounding area faster than the stamped area. Thus, after cleaning and burnishing the area, apply an acid. The serial number will emerge above the surface of the softer unstamped metal. Fry's reagent is often quoted as the etchant. Possible suppliers of do-it-yourself kits:Scenesafe - Solihull, Birmingham (UK) which sells forensic science equipment. They sell an "Etching Kit" which is said to contain all the equipment that you are likely to need to restore erased serial numbers and stored in 60ml bottles within a handy carrying box. Forensic scientists suggestions: Recipe 1:40 mls of hydrochloric acid 5 g cupric chloride 30 mls water25 mls of ethanol or methanolRecipe 2: â Fryâs Reagent40 mls of hydrochloric acid 5 g ferric chloride30 mls water25 mls of ethanol or methanolThe surface is to be cleaned (removing rust paint and grease) and the mixture applied with a cotton bud. Fry's Reagent is a similar recipe but uses ferric chloride in place of the cupric chloride. Recipe 1 gives better results than the ferric chloride recipe of Fryâs Reagent but the presence of copper creates a messy coating, which can easily be cleaned off.