Powdercoating barrels ??

[AlphaDogChoppers]

. I handed back parts twice to one guy cause of bubbles in the finish.

That's why I always heat my parts to full temperature before applying the powder. If there are sub-surface impurities that are determined to outgas, it gives them a change to do it before the powder is curing over top of it.

If that coater had any sense of pride in his work, you would have never seen it before he fixed it.

 

[VonYinzer]

I think the bullshit stems from one thing... Poorly applied paint or powder. When applied properly, as Joe said, no problems. The issue stems from guys putting 8 coats of fuckin' paint on every part of the motor.

 

[el_simo]

Some lads just don't care its a pay cheque to them either way . Don't know of many bikers doing it over here

 

[jessezm]

The one thing to keep in mind is that when you bake the cylinders after coating, your sleeves can loosen up, and when they cool back off they can end up standing a bit proud. Someone over on SOHC4 just had this happen with powder coating. If that happens, you just need to make sure that you get them back into the right position, and it may take a machine shop with a press to do that, or re-heat them yourself and make a clamp to hold them in place while they cool.

I'm not saying this WILL happen, I'm just saying it's something to watch for!

 

[JRK5892]

sounds like the coater did not have a temp controlled oven and ws prob using a household oven... this does not happen if propper coating is taking place... at 375 - 400* for 30 - 45 min sleeves will not come loose at all. sounds like the coater did not know what they where doing or how to guage the item Part metal temp for cureing

 

[AlphaDogChoppers]

I have another theory. The jug may have been junk. I have never heard of a sleeve coming loose or moving. If I had a jug that did that, I would throw it away.

 

[citizen clive]

If you're concerned about the heat, how about a heat dispersant coating there's a few around.

http://www.techlinecoatings.com/introduction.html#thermaldispersant

 

[crazypj]

mert

sounds like the coater did not have a temp controlled oven and ws prob using a household oven... this does not happen if propper coating is taking place... at 375 - 400* for 30 - 45 min sleeves will not come loose at all. sounds like the coater did not know what they where doing or how to guage the item Part metal temp for cureing

It's real common to heat Japanese cylinders to about 350~400f to remove sleeves, I've done several hundred
I forget what Harley call their process but they use rough cast liners, machined on ends only so the reduced diameter holds liner 'centered' and cylinder fins are cast around it.
It isn't possible for HD liners to come loose

I agree with JRK. The idea that powdercoat retains heat is just so much bullshit. No more heat retention than paint. Polishing makes a slight difference in heat dissipation because a polished surface has slightly less surface area than a rough surface. Still, die cast aluminum is already a LOT smoother than sand cast aluminum.

'Sunny how something with no factual basis can get repeated so many times that it takes on the apearance of truth. <G>

As soon as a surface coating gets over 0.015" it starts to act as an insulator.
Multiple tests were done in the 1950's when Vincent were using enamel on engines.
Type of coating doesn't matter, just the thickness.
Primer before paint is probably a bad idea on non-water cooled engines