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General Category => General Discussion => Topic started by: Dirk_S on September 25, 2022, 10:20:19 AM
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With the engine off the bike and about to be rebuilt, I’m considering stripping the paint, something I’ve been interested in doing for a couple years now. The Guzzi engine is lovely to look at and doesn’t deserve to be hidden in black. What are the pros and cons to doing this besides potential for chalky oxidization? Would the engine performance benefit by dissipating more heat?
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If the paint starts looking bad, I strip it. Bare looks better. Transmission too. Much easier with the engine out and I wouldn’t strip it unless it was out, but it ‘can’ be done
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If the engine is out, now’s definitely time to do it. I would leave the fins on the cylinders and heads black. IMO, that looks cool.
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WD40 will have enough residue to prevent aluminum getting chalky.
Back in the 1950s BMW recommend washing their engines with gasoline. The aluminum on those engines are very porous. When cleaned with DeGreaser they become very chalky. A little petroleum coating creates a warm glow.
Don
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The black will help in the case because it radiates much more energy than silver surfaces. This is why cast iron stoves are black. Think of black as a conductor of radiant heat and silver as a resistor.
But either finish will radiate "enough" heat.
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ACF-50 will keep the bare aluminum bright for years, spray it on, let it sit for a couple hours, wipe off the excess.
Seals the surface, best stuff available for protecting bare aluminum, developed for the Harrier Jump Jets to resist salt water corrosion.
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Yes, technically a black body is the best radiator of heat (that's being used as a verb). Practically for an air cooled engine, it will not make much difference - the fins are there to increase surface area to air flow, so you lose most of the heat by conduction.
First time I saw a general aviation plane's motor I was astounded. The cylinders' fins are quite thin and far more numerous than an air cooled bike's engine.
I was told that vapor blasting - pumping glass beads and water at aluminum peens the surface and it will stay clean and shiny longer than simply using something like ZepAlum or a similar acidic product.
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With the engine off the bike and about to be rebuilt, I’m considering stripping the paint....
Not sure if you mean you want to do it or have it done and if literally stripping or blasting.
My experience was awful.
It took me a month in summer time, outdoors.
It was fun at first, when most of it bubbles up.
Cleaning every cylinder fin was a major hassle.
I had to soda blast it in the end. Little specs of paint will be noticeable.
But now that it's done, the shiny aluminum looks really nice.
As mentioned above, ACF50 will keep the chalk at bay.
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Not sure if you mean you want to do it or have it done and if literally stripping or blasting.
My experience was awful.
It took me a month in summer time, outdoors.
It was fun at first, when most of it bubbles up.
Cleaning every cylinder fin was a major hassle.
I had to soda blast it in the end. Little specs of paint will be noticeable.
But now that it's done, the shiny aluminum looks really nice.
As mentioned above, ACF50 will keep the chalk at bay.
I was planning to do it myself. Is it economical enough to find a blaster and soda right off the bat, or take it somewhere to have it done? My V7’s heads don’t have paint on them, but I could totally see some of the ribs and crevices on the Guzzi block being a bit of a niggle.
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Good vapor blasting is pretty reasonable. I think having my G5 bare crankcase, gearbox shell, cylinders, heads, timing cover, borranis, carbs and fork legs was about $600.00. Pulling the crank and all the seals and bearings and tearing the gearbox apart is a little time consuming but - wait never mind.
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ACF 50 after stripping. But, the hard part is stripping. I had a professional service remove the paint. The soaked, bead and vapor blasted to get it off. They said some came off easy and some was hard to get off. Lots of grooves, corners and holes to get the paint out of. The finish is not smooth and bright, but not dull gray. I like the cleaner look.
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Appreciate all the responses.
If I have someone vapor or bead blast it for me, I was hoping to not have to tear down the gearbox or final drive, or remove seals. Is this doable, or do I need to remove everything?
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Appreciate all the responses.
If I have someone vapor or bead blast it for me, I was hoping to not have to tear down the gearbox or final drive, or remove seals. Is this doable, or do I need to remove everything?
IMHO if your blasting, it needs to be torn down. Just too much chance of stuff you dont want, getting into places you dont want it to be. Im kinda scared of the thought of this post... My 02 stone has the infamous black "bubble paint" on it that tends to flake off with time. So far so good, but I know one day it will start, and ill have to strip it all down.
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When I worked in the aircraft shop I did a lot of bead blasting. It took me two days of constant blasting to remove the paint from seven radial cylinders. The ones we sent for plating were blasted by the plating company. I was told they used garnet media.
kk
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I had the engine, transmission and final drive soda blasted on my CX but that was just to clean up and not removing a painted engine, etc. Just the intake, etc. were covered. The guy who did it had a mobile unit that he did entire cars so I assume a painted motorcycle engine wouldn't be a problem.
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^^^^ What Tom sez. As far as I know, soda blast is doable without tearing everything down.
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ACF-50 will keep the bare aluminum bright for years, spray it on, let it sit for a couple hours, wipe off the excess.
Seals the surface, best stuff available for protecting bare aluminum, developed for the Harrier Jump Jets to resist salt water corrosion.
Dang Canuck beat me to it. I WISH i would have had the chance to douse every nook and cranny of my bare aluminum AMBO engine in ACF-50 before it went in the frame.
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Vapour blasting will NOT remove paint, if it does it will take hours to get the paint off a small area. My vapour blast cabinet is a fantastic tool but a paint remover she ain't. In addition, I don;t think it is possible to seal up an engine (without extensive effort) to vapour blast a complete unit. You would be amazed how the media is forced into the thinnest gap between pieces, it will pass through any weakness in a component gasket.
I would recommend soda blasting for an in situ engine strip. You may want to attempt a carefully masked application of aircraft paint stripper in an aerosol can to soften the paint surface and then hit it with soda. From experience doing what you are attempting it has taken several applications of paint stripper followed by soda and repeat, repeat , repeat until its all gone.
You may not like the finished soda blasted appearance and if that is the case you can hit the stripped surfaces with fine glass bead fed from a simple plastic pail of bead and a siphon type compressed air sprayer, probably the same unit that you will use to spray the soda. You are going to need a pretty good air supply though.
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If soda will do the trick, then all the better since I at least have the opportunity to do at at home (outside, no garage, easy to wash away from what I’ve gathered).
And noted on the oil treatment afterward. Don’t want my bike looking like it has a cocaine habit.
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It's one of those things you have experience to appreciate the pain.
As Canuck says, you need the appropriate air supply. I borrowed a 26gal 5cfm compressor and had to wait for it to recharge, added to the frustration.
About the soda, you might have read that it kills grass.
Mine turned brown but didn't die. I kept watering it.
I bought the 50lb medium grade from HF. Almost used it all.
I hacked together a blast tent. Keeps the mess down and saves on soda.
Good prep is key to avoid blast material getting in the engine. Don't spray directly at seems and covered holes.
Here is the fun you're heading for: https://wildguzzi.com/forum/index.php?topic=102352.msg1691648#msg1691648
Hurry up though, it's getting cold around here.
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If you just want to remove paint, I would soda blast it.
I soda blast things regularly when I don’t want the destruction of glass bead or regular “sand”, black beauty, etc. Get a hand held unit like a good Speed Blaster or HF china knockoff. You’ll use lots less air without having to suck the soda (or other media) into your air stream- never had any comparable success with a siphon-type sandblasting kit, especially with baking soda. Soda clumps very easily and I want equipment that’s easy to service to clear those clumps. A little hand held gravity pot makes it easier to keep the media dry too. Wear a mask of some type to keep your sinuses from pouring a waterfall into your dry media…. The grass and leaves will grow back.
Just know it will also strip coatings on ferrous items like engine fasteners. Then they will rust like a rocket and can corrode if soda is left between the ferrous parts and alloy parts. Neutralize/Clean it super well afterwards and do what you need to do to stop rust and corrosion from starting- clear coat paint, ACF-50, oil, whatever. Ferrous parts will flash rust as soon as it gets wet.
It’s a PIA to mask a frame perfectly to do this. If you can do it with engine, whole or in pieces, out of the frame, do it. The same applies to doing it with all the ferrous parts removed.
Soda won’t etch the base material. You’ll need to use some glass bead or similar to make the surface fancy…
Edit- fwiw, we’ve blasted multiple assembled engines with everything from soda in a hand held Speed Blaster gravity rig to Black Beauty in a pressure pot. It can be done with no ill effects if you’re careful and not worried about what the purists think….
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OR, If you decide to keep it black---POR15 Chassis Black matched my EVT and Cagiva black engines perfectly. I've heard some people use black shoe polish for touching up (I don't know if it works)
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Soda blasted aluminum rim, it dulls the finish but it sure gets all the corrosion and paint off
(https://i.postimg.cc/WbXLrpWK/DSC04476.jpg) (https://postimg.cc/SJ2vb4p7)
A Ducati 860 Bevel motor taken out of the frame and every opening sealed with plugs and silicone, before
(https://i.postimg.cc/nLJ5Mqht/IMG-3648.jpg) (https://postimages.org/)
after glass bead blasted outside on the driveway, glass bead blast will shine up the surface but you have to really seal up the motor carefully
(https://i.postimg.cc/VkRTrdrr/IMG-3650.jpg) (https://postimages.org/)
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Looks good, Jim.
Soda blasting polished parts is an easy first step to polishing with solvent and 1500+ grit & finer sandpaper. It can eliminate any small bits of hard grit caught on the surface so they don’t inadvertently cause deep scratches..
Whenever I blast with a hard grit (glass bead, etc) outside, I do it over a large tarp. It helps with clean-up, but more importantly it captures the fractured media that is too heavy to be carried away by wind as dust. This media will still cut so it is sifted and saved to be used for lighter duty blasting like producing a finer finish on metal. Sometimes even the dust is kept and used to blow the job, depending upon the project. Learned this doing monument s/b work to produce a different finish on the stone. Guzzi people aren’t the only ones who are cheap….
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Really like that glass bead texture. What will it look like with just the soda treatment?
I think I’ll stop by Harbor Freight in the next couple days and grab a gun and some Armex extra large media. I have a pancake compressor, and figure if it’s not big enough for the job, I can rent one.
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Really like that glass bead texture. What will it look like with just the soda treatment?
I think I’ll stop by Harbor Freight in the next couple days and grab a gun and some Armex extra large media. I have a pancake compressor, and figure if it’s not big enough for the job, I can rent one.
I believe you need a minimum of 3hp compressor for those hand held blasters.
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Really like that glass bead texture. What will it look like with just the soda treatment?
I think I’ll stop by Harbor Freight in the next couple days and grab a gun and some Armex extra large media. I have a pancake compressor, and figure if it’s not big enough for the job, I can rent one.
Soda alone will look like the rim in the picture I posted. Soda is non reusable where as the glass bead can be recycled. Use a fine glass bead like #7. You don’t need a big compressor if your patient and give the compressor time to recharge.
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Just a follow up now that I have pictures to share, I ended up getting the motor and swingarm Stripped professionally. They used plastic material so that it wouldn’t potentially harm any internals. 98% of the exterior has been stripped, only a few minor areas still have black powder coat on. Would’ve liked to have gotten the surfaces bead blasted, but I’m happy enough with the results to throw it on.l as-is.
(https://i.ibb.co/Wgn3zSt/258037-B6-30-FA-4885-B29-F-0-D9-E167-F7948.jpg) (https://ibb.co/Wgn3zSt) (https://i.ibb.co/gd4x7cL/D7-D1-B893-4700-4-F73-881-D-DFBA6-D8-A2-C83.jpg) (https://ibb.co/gd4x7cL)(https://i.ibb.co/nRt6ZVY/C9200-DBE-B261-4-F97-AD70-1-ED2-A0868872.jpg) (https://ibb.co/nRt6ZVY)
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The raw aluminum casting will get blotchy and gray as the surface oxidizes.
It'll still run fine, but look aged. My T3 is proof of this.
But if you spray it down often with ACF-50 (or WD-40) and blow off the excess the finish will maintain a reasonably even grey color.
More detailed cleanup can follow with an occasional bath with WD-40 and a scrubbing brush.
Thanks, Ron. As mentioned earlier, I was aware of the chalky corrosion that’s inevitable if I leave it dry. I don’t have any ACF-50 at the moment, so I was considering a silicone spray or WD-50.
I failed to mention early on that one of the reasons I decided to go with the bare look was because shortly after buying it, I followed someone’s bad advice and attempted to clean the engine with oven cleaner, not realizing what havoc that would wreak on the painted finish. Since then I’ve had an ugly alternator cover and a few other areas that stuck out. Instead of repainting it, I thought I’d take the opportunity to be unique, and give it an old school look, which may or may not additionally prove beneficial when I take it off the beaten path as I do.
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Looks great, Dirk.
Those cylinder fins are the hardest to clean up, even with paint stripper.
Reassembly is the fun part.
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Silicone spray can lead to adhesion issues if painting is involved in the future.
Another option to consider for equalizing the blotchy surface and incidental removal of some remaining coating is to use full strength blue a/c condensing coil cleaner. It is a caustic product in terms of pH that is specifically formulated to clean and brighten (attack..) the aluminum fins to benefit heat transfer. Apply, let rest and rinse off as instructed. Repeat as needed. It’s around $60/gallon for full strength pro stuff by the single jug unless you buy it in bulk by case or pallet as a pro, where it only costs around $20/gallon. So find a pro that’s a friend…. If you can find the diluted consumer squirt bottles, it’s largely useless imho. A friend that restores old HD bikes and carbs uses it and it can produce great results.
I’ve found that the first few rounds don’t seem to do much. Be patient, do several application cycles. Even though it’s attacking the metal, it’s a slow process when done correctly. the change between each application may not be dramatic but the before and after pics of the whole process can show much more obvious changes.
It doesn’t disrupt the surface like blasting or abrasion can, so for pretty castings it’s a nice way to make them look new again.
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Timely thread as I am soon to drop my engine out and give it the "full treatment' , wanting to leave it bare but unsure about the oxidization. I will pick up some of that ACF-50. Hoping that an ännual"treatment will suffice...