Removing Plastic Coating

[Dilkris]

I have a classic motorcycle where the frame number is (typically) stamped into the head stock.
On my bike the frame has been plastic coated by a previous PO and whist I can just make out the number, I need to play around with a torch, creating shadows to read the number.
In effect the indentations of the number stamped into the frame have been inadvertently filled in with "plastic."
What is the solution to this? Can you locally burn off the plastic in the area of the frame number with a micro torch or similar?
I am surely not the only member that has been faced with this problem - what's the solution?
Help !!

 

[MetalMonkey]

How many times do you need to read the number? As long as you now have a record of it leave it alone would be my recommendation.
Disturbing those types of finishes usually ends up with rust creeping underneath and the entire thing then needs redoing.

 

[Barking Mat]

Abrasives ? Power sander ?

 

[Dilkris]

How many times do you need to read the number? As long as you now have a record of it leave it alone would be my recommendation.
Disturbing those types of finishes usually ends up with rust creeping underneath and the entire thing then needs redoing.

I agree - I personally do not want to read it - it is something important to a prospective purchaser.

 

[Dilkris]

Abrasives ? Power sander ?

I thought about this but worried that I might compromise the stamped letters/numbers.

 

[Ross365]

I've use this Wickes' stuff a lot over the years on all kinds of tasks https://www.wickes.co.uk/Wickes-Paint+Varnish-Stripper---1L/p/155054
It can be a bit slow sometimes, but very often does the biz - and it's also very safe.

 

[JOEPRO]

Or use one of those cheap spot blasters with the rubber tips for bodywork and shot blast along the vin then follow with aerosol satin black

 

[cheb]

How about chiseling the plastic out from the letter grooves with a very fine point, a scalpel or suitable hypodermic needle might do it.

 

[RichardM]

Scrape the plastic coating off the numbers with a Stanley knife blade. If you are careful you can just do the strip along the numbers, then cover with clear tape.

 

[ms08]

Could you highlight it if only to read with white powder - talc or flour springs to mind or even white paint?

 

[Dilkris]

The problem I have is that on classic triumph motorcycles, in the later years, (1975) Triumph also stamped "Triumph" in and around the engine number - with the plastic coating, the engine numbers are just discernable with a torch shone at the right angle, BUT the plastic coating has completely hidden these "Triumph" stamps. It is these that I am trying to determine exist.

 

[Dragnet]

Heat gun with a shield so you only heat up the area around the number? Imagine the sheets with a hole around the area of interest that surgeons use, but in something rather more sturdy. You may be able to carefully scrape the softened coating off the number cartouche without affecting the rest of the finish. A lacquer over the top would preserve the overall effect, if you could test for a reaction with the plastic coating first.

 

[Gragson]

Without seeing it, so a bit of a guess, and what I have done to relieve stamped metalwork on previous bikes.
Acetone on a cut to size clean bit of old cotton t-shirt, tape it on, leave for a bit, nylon brush, repeat until happy, best to mask the area as acetone will soften surrounding paint work.

 

[Dilkris]

Without seeing it, so a bit of a guess, and what I have done to relieve stamped metalwork on previous bikes.
Acetone on a cut to size clean bit of old cotton t-shirt, tape it on, leave for a bit, nylon brush, repeat until happy, best to mask the area as acetone will soften surrounding paint work.

Does this work with Plastic Coating Gragson?

 

[Gragson]

Best to post up a pic. Acetone will break down/melt powder coat, but you need to control it so does not run off as it will damage finish in areas you don't wont.
Post up pic

 

[RichardM]

I have removed polyester coating with acetone before, but as above you need to be careful if just wanting a "spot" removed. If you know the position of the logo in relation to the numbers l would still scrape the coating off with a Stanley blade as the most controllable method.

 

[Dilkris]

For everyone that advised me on this, many thanks - this is the outcome and what I did.
The engine number was "just discernable" in the right light but there was a requirement to confirm that the "Triumph" stamps were also there.
I masked off the area and treated with Nitromors, waited 10 minutes, then scrapped off gently the softened layer with a wood chisel wide enough to cover the full width (plus) of the stamped area. (I obviously did not wish to risk scratching the "footprint" of the frame numbers as this could have raised the question of possible tampering.)
I had to repeat the above process multiple times (actually 8) before I got down to steel - it took 2 hours.
I finally cleaned with Acetone (which I think did very little) and ultimately polished gently with a brass wire wheel in a Dremel.
If you zoom in on the finished result, the Triumph stamps can clearly be seen.