To paint or not to paint (the engine!)

adi1974

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so I'm in the middle of a top end rebuild and cleaning things up ready for reassembly. I was planning on scuff polishing (satin not mirror) the side covers so it doesnt look too shiny, just aged and clean. My question is what to do with the cases, barrel, head & cover?

I had assumed once clean I needed to paint them (HT) but then got to thinking, can they be left bare and just cleaned up? I'm not massively into how the paint can make the engine look a bit artificial for a while if you know what I mean. I like a bit of character but I want it clean and tidy.

Any advice / thoughts? Cheers

ps. What rotary tool (like a dremel) attachments are good for cleaning up / light polishing between the fins?
 
I personally do not like painted engines in a vintage bike . I think painting would be a mistake, just think how awful it will look when that paint starts to peel and flake. I think all you need to do is de-grease the engine.
 
I have to agree with Scambled. I've attempted to repaint two engines. Both with High Temp Engine Paint in a rattle can. My success was limited. One the paint did not hold up to gas and oil well, and I ended up stripping it back to bare aluminum. The other is holding up better, but every spring I have to touch it up where it flaked or chipped.

My current build, I just degreased and scrubbed it with a wire brush.

On the other hand, if the engine is already disassembled, and I had the resources to prep and paint lower end properly and possibly the jugs. I might consider it.
 
Thanks guys, to be honest I'd much rather keep it bare. I like the look of it. Looks lived in like good old leather does. For some reason I assumed it had to be painted (apart from the side covers). Reckon I'll start cleaning it up and see what what pops. :)
 
Putting a film of paint on the bare fins adds resistance to heat transfer from the jugs to cooling air. Although Yamaha painted them on some models, IMHO, it just doesn't make any sense.
 
My bike's outer cases were all scratched up, so I painted them but left the jugs/head natural aluminum. That comes from way back when; when I was doing Honda SL's as MX bikes (damn that was a long time ago) Powroll (another old name!) sent out a letter with each big bore kit they sold where they discussed painting the cylinders. Their finding was that the painted cylinders almost always had seize marks, the unpainted ones did not. Their conclusion: don't paint the cylinders.

In this day and age, there is no reason the jugs/head could not be anodized black (or whatever color you want). IIRC anodizing has no effect on heat transfer.
 
Thats pretty interesting about the hot engines and paint. Good food for thought.

What dremel type attachments are best for cleaning up those tricky fin areas? Anyone got any tips, bought a little rotary tool (like dremel) to help but dont know what attachments are best for the purpose. I'm guessing wire brushes and maybe scotchbright wheels (if I can get any in the UK)
 
FWIW, at one time Harley allegedly sold a heat transfer paint. Powroll mentioned that in their info sheet but it's not on their web site. When I bought the aluminum radiator for my race car, there was a tag in the box which said 'don't paint'.
 
Thats pretty interesting about the hot engines and paint. Good food for thought.

What dremel type attachments are best for cleaning up those tricky fin areas? Anyone got any tips, bought a little rotary tool (like dremel) to help but dont know what attachments are best for the purpose. I'm guessing wire brushes and maybe scotchbright wheels (if I can get any in the UK)

I use a wire brush with long bristles... Something like this http://www.harborfreight.com/steel-bristle-brush-38491.html
 
Wire Wheel will do wonders to an engine. I too like them raw, always raw.
Harbor freights standard 4 1/2" Wheel is the main force behind it.

For the small stuff, HF also has these small ones:
http://www.harborfreight.com/6-piece-wire-wheel-and-cup-brush-set-1341.html

Now for the small ones i posted there, those are wayyy too coarse, they just leave huge scrathes only. There's another set not listed on the site, it is used for Demels n Drills aswell, they're a hair smaller in size, the spindle that attaches to the chuck is bit smaller than those posted ones aswell. They are really soft and come in either Steel or Brass.. Go with the steel, the brass would be so soft you'd almost not see results from em...

This is only my first pass, by the end it should be looking rather good.

IMG_3326-1.jpg


In the frame, as the picture is now, it looks good; finished even! But I'm still workin... Fine detail, real easy with those two sets of brushes, just takes time. With anything in terms of polishing and shining stuff up, just takes time, but you get there..
 
I would definitely recommend against painting the engine. I did mine many years ago and have regretted it ever since.
Aside from the aesthetics and heat-dissipation issues, once painted, you'll need to repaint it every other year to keep the engine from looking grey.

In fact, if anyone knows how to remove engine paint without either removing the engine from the frame (I don't have access to a garage) or damaging the surrounding frame paint, please let me know. I'd love to return the engine to its OEM appearance.
 
wish we had HFT in the UK. Sadly we dont. I've just spent the last couple of days going around all the motor and tool shops in my area (Bristol) and havent found the right things for the job. Most of the wire brushes I've found have been too wide to fit down between the fins or not long enough to then reach. All the shops I've been to pretty much have exactly the same things and they're really poor. I'll have to try some from the web but I'd have prefered to see before I buy and also not pay postage. I'll keep looking.

In the meantime, done a fair bit of degreasing, just need some stuff to get all the crap out and lightly polish it up between the fins. Thanks for the replies so far
 
Cleoncleon...Just a quick question...after you polish and get the engine looking like that...What do you use to get it to stay that way? Isn't the motor more inclined to rust with out the finish on it? If you do coat it with a clear coat of some kind do you have a recommendation of which brand of clear coat?
 
I know there's some better stuff out there, like wax's and such.. but I've found em not needed really. Steel would be even more prone to corrosion, the engine aluminum is pretty tough. Use the WD/40 + Engine oil combo. Just give it s few light rub down from time to time, what ever is raw. To keep the shine, the key is to have the metal absolutely clean throughout the process. Mine shines but not like a 'polished with brown/white compounds' shine, but just enough... But in that regards its a personal choice..
 
If you have access to a pressure tank blaster you can use plastic media or baking soda, remove what you do not want hit by the abrasive and double tape any openings with duct tape, also tape the frame rails with a few lenths of duct tape as well. Unless your pulling the engine. The plastic media will not hurt chrome, baking soda will cut it slightly. Any blasting facility will do the job for you, but I would recommend taping up all the openings your self. You don't want anything going internal. You can get a small handheld blaster from harbor freight that holds about 3 cups of abrasive and if you have a small air compressor you can do it yourself, then you know your not filling your motor up with dust from the media. Don't use sand or glass beads, they are agressive and you just want to restore the soft grey finish of the heads and lower end, everything else you can polish. Baking soda works good, but you will go through some boxes but the residue will wash off with water. Experiment with air pressure to see what works best, 30 to 40 psi works to pull the baking soda out of the hand held blast guns, but the tank units will need max. pressure and the commpressor will run endlessly trying to keep up with the tank dropping in pressure.
 
Mine , prepped ,masked & sprayed in the frame. I messed up time-wise on this rebuild so stuck a 'dirty' engine in.
I prefer a freshly vapour-blasted finish but even that wont last long on British roads, wet , muddy & salty!
For that reason I give mine a light 'mist coat' with standard auto rattle can paint (Ford Strato Silver here if I remember rightly)I dont need/use heat-resistant paint , so long as its thoroughly cleaned and sprayed onto a slightly warm engine it works treat,for instance this one has now done nearly 2,000 miles & looks as good as new.No overheat issues as its had such a light coat, not a 'blanket' !
I spent a day cleaning the motor with toothbrushes, steel-wool, cellulose thinners & washing detergent , ..
This shade of silver is perhaps a little too 'bright' ,but the 'Strato' is what I found on my shelf at the time..

xsaugust2012005-1.jpg
 
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HFT a couple of bikes never had a problem with heat or chipping. If you prep the metal and apply the paint and bring the motor up to the temp it needs to cure, you wont have a problem. I prefer the black with silver fin look myself!
 
I use automotive grade acrylic enamel with a coat of urethane clear. I've painted lots of motors with no heat problems even after years on the road. Lighter colors do have a tendency to discolor a little around the exhaust ports, but not enough to worry about. As far as Big Bore kits are concerned I can see problems with using paint. Someone mentioned the Harley Heat Transfer paint. They quit using that after the EVO engine came out with no cast iron parts. It could probably still be sourced thru the aftermarket. V-Twin, or J&P Cycle comes to mind.
 
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