powdercoating cylinders

seattle##gs · Nov 23, 2016

in theory the ideal time to powdercoat cylinders would be before they are bored but in the real world will there be a problem powdercoating AFTER boring?

texasSlick · Nov 23, 2016

I would not powder coat cylinders. Powder coating relies on the electrostatic attraction of the powder to the part. The electrostatic field between the fins is irregular and non uniform. As a result, powder tends to be of non uniform thickness between the fins. Moreover, powder thickness is greater than paint, and this tends to reduce heat transfer.

It should be obvious that a thicker film on the fins is a greater impediment to heat transfer. Not so obvious, but a physical fact nevertheless, is heat transfer is enhanced if the fin surface is rough. Powder tends to smooth out the surface roughness more than paint.

Slick

gortnipper · Nov 23, 2016

texasSlick said:
Moreover, powder thickness is greater than paint, and this tends to reduce heat transfer.

It should be obvious that a thicker film on the fins is a greater impediment to heat transfer. Not so obvious, but a physical fact nevertheless, is heat transfer is enhanced if the fin surface is rough. Powder tends to smooth out the surface roughness more than paint.

Slick

I think Comnoz found it made no difference whether barrels were painted black or silver, or powder coated: heat transfer was the same and barrel material was the differentiation, not surface coating on the exterior.

barrel-coatings-test-t21701.html

Jerry Doe · Nov 23, 2016

On my recent 750 build I powder coated the cylinders. I have no over heating issues and they look great.

Fast Eddie · Nov 24, 2016

I would say it depends entirely on he powder coater. A really good guy may well apply it thinly and be able to reproduce the Comnoz 'it makes no difference' findings. A bad one will apply it so thick it'll be like being wrapped in asbestos !

As to the original question, I would say that the boring process will cover the block in oil and suds etc. which could soak into the pores of a bare casting and compromise paint adhesion unless they are scrupulously cleaned afterwards.

Whatever you do, don't do what some idiot did recently and put them in the dishwasher to clean...

They come out looking like they've been on the sea bed for 50 years

kommando · Nov 24, 2016

Been powdercoating barrels for years and no issues, look good and very durable.

toppy · Nov 24, 2016

No issues with mine either and the engine is regularly above 4000 rpm for more than half an hour at a time. I are coated in all the little nooks and crannies an it has an even gloss black finish. It was done after being bored and then having the bores carbide coated by Laystalls. I had tried painting but was not happy with the finish so a small local business did it an charged £15 which was less than i spent on paint! Took them few days i had been at the job for two weeks! All threads an gasket faces were masked off an coating was only where it was supposed to be. I believe just as with painting or plating the skill of the person who is doing the job plus the level of preparation an attention to detail are the key to success. That firm does all my an my friends coating jobs an i will not think twice about having barrels coated again.

DogT · Nov 24, 2016

Convection heat transfer overwhelms the radiant heat transfer by orders of magnitude. Radiant heat transfer of the barrels is of minuscule proportions. Nothing wrong with powder coat if that's what you want to do.

MS850 · Nov 24, 2016

I painted my cylinders with VHT engine paint and cured them in a old smoker, they have held up well and stayed shinny. MHO.

kommando1 · Nov 24, 2016

I powder coated mine 12 years ago, and they still look perfect. They looked awful when I spray painted them, never an even coating.

Fast Eddie · Nov 25, 2016

Finding a good looking and durable silver paint for the barrels defeated me, twice!

Powder coating for silver barrels certainly sounds like a sensible option.

nickguzzi · Nov 25, 2016

Be interesting to see if anything has changed. I had the guzzi's frame powder coated in "silver", anywhere anything touched it it turned battleship grey - and has remained that way.
It has been fairly ugly now for quite a few years. You can't really see it from the seat, and my guzzi doesn't need too much messing about with.

kommando · Nov 25, 2016

My current powdercoater clear coats silver unless you request otherwise, this does not change colour. If you get it without clear coat then it will turn grey and T cut does it in seconds which is how I found out, which I use as the coating for Norton Commando yokes and front mudguard stays as they are grey and not silver.

B+Bogus · Nov 25, 2016

+1 on the silver powder coat bad experience. I've no idea what that stuff is good for!

2-pack, especially for silver is the way to go. I understand it's now available in a can, but I'm fortunate enough to have access to 'proper' facilities.

Another good cylinder paint is PJ1 Fast Black. I used this on my first 850 resto 5 or 6 years ago and it's still holding up just fine. It also self levels well, and looks like powder coat.

mschmitz57 · Nov 25, 2016

seattle##gs said:
in theory the ideal time to powdercoat cylinders would be before they are bored but in the real world will there be a problem powdercoating AFTER boring?

Uhhh... To answer your original question, I would use a good spray detergent, like Simple Green or Spray Power, and scrub the cylinder in a tub of really hot soapy water after honing to remove any trace of oils. Also be sure to wipe down the bores (piston and tappet) with light oil like WD-40 afterwards to keep it from flash-rusting. Other than that you should be fine. If you heat the cylinder before cleaning with a torch and keep the scrub water really hot, the cylinder will dry quickly from the stored heat. Use compressed air to blow off the residual water. Dry it quickly otherwise it will rust before your eyes. I like to give the cylinders a good hot bath in strong detergent solution after honing or bead blasting to remove any grit and oils before painting.

kommando1 · Nov 27, 2016

kommando said:
My current powdercoater clear coats silver unless you request otherwise, this does not change colour. If you get it without clear coat then it will turn grey and T cut does it in seconds which is how I found out, which I use as the coating for Norton Commando yokes and front mudguard stays as they are grey and not silver.

Interesting!,
My Guzzi Wheels were powder coated silver by a reputable business and I only saw them in "Battleship Gray" immediately afterwards. I was told that because the process was done in the winter (I'm in California) that the high humidity caused a darker shade to occur. I talked to another powder-coater who said that high humidity can cause this. I plan to re-do them when I can afford it, or was I conned? Thanks.

pommie john · Nov 28, 2016

I had mine powdercoated in a heat resistant satin/ slightly wrinkle finish.

Very happy with the result. It seems quite thin so I'm not worried about heat transfer.

MS850 · Nov 28, 2016

pommie john said:
I had mine powdercoated in a heat resistant satin/ slightly wrinkle finish.

Very happy with the result. It seems quite thin so I'm not worried about heat transfer.

pommie john » thats a nice looking bike you got there!

Madnorton · Dec 2, 2016

Found a powder coater in the UK who is prepared to use the HT powder from the states, just need to get a sample from the UK supplier, they hold it here but they have only ever sold it to stove manufacturers due to the cost of the powder - not cheap but would go a very long way. They can get any colour and finish if need be.

Fast Eddie · Dec 2, 2016

Madnorton said:
Found a powder coater in the UK who is prepared to use the HT powder from the states, just need to get a sample from the UK supplier, they hold it here but they have only ever sold it to stove manufacturers due to the cost of the powder - not cheap but would go a very long way. They can get any colour and finish if need be.

Great!
Who?
Where?

powdercoating cylinders

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