The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Gallinazorey on March 12, 2009, 09:14:31 AM
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[size=14]Gentlemen,
For some time now I have wanted to sand blast my cylinder heads and take all the white rust off. Has anybody done it before? I am thinking of buying a cheap portable sand blaster on Ebay and hiring the air-compressor.
Can I do it while the cylinders are on or is it advisable to take them off? If I take them off with what should I cover the inside so I don't damage it? Any tips?
Thanks guys
Eric[/size]1979 R65 in London, UK
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I would choose a less 'aggressive' blasting media than sand.
Aluminum is quite 'soft' as compared to iron or steel material.
Glass bead, or something more like crushed walnut shells.
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+1 with Bob - Sand is pretty rough on the relatively soft alloy these things are made of. If one has alot of patience, some people have obtained good results simply using some of those non-metallic scouring pads (for use on non-stick cooking pans) and a general degreaser like WD-40
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I have seens a BMW that had been sand blasted, after it had been through the following winter in our wet English weather. It was not pretty. Like others have said sand is too abrasive. It creates much surface area for new corrosion to take a hold. Do you like white fur and a patchy finish?
Use a less abrasive media.
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I have had aluminum cases bead blasted and the result was not great. It actually changes the texture of the surface a bit making it look odd. As the others have said use a "soft" media on aluminum. It looks like you just want to clean up the surface. Why not try a nylon bristle brush and a mildly abrasive powdered cleaner no compressor needed? Soda blasting is also a non damaging option. A pressure washer may also do a decent job. Check with a marine supply house they may also have a chemical product but if it contains hydrofluoric acid be very very cautious. As for doing them in place good prep and careful application may prevent unintended contamination of internals. Rinse and repeat. ;)
rich
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I had the cases and barrels of the R100 soda blasted - a beautiful job.
It is simply bicarbonate of soda, produced by Arm & Hammer (the toothpaste guys ;) )
IIRC, they were beadblasted first, to remove the heavy crud.
The soda gives a very pleasant matt finish.
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Wow! Nothing says it like pictures! I doubt I get them like that with my toothbrush though I am sure I will get a definite improvement. This finish you show us here is what I want to achieve....beautiful!
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It is simply bicarbonate of soda, produced by Arm & Hammer (the toothpaste guys ;) )
No. it's not at all plain ol' baking soda. Soda blasters utilize an entirely different compound. Very popular with auto resto work as the soda will slowly remove the paint without damaging the tender sheet metal. Not a good choice for actual rust removal as it is too gentle for that type of work.
DIY soda blasting generates a terrible mess and you'll need to invest in the appropriate safety gear to protect your health. Costs continue to mount...
Unless you plan on using the blast equipment regularly, it would be more economical to farm out the work and save some cash.
Monte
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When Bob Grauer rebuilt my heads, he cleaned them with glass beads.
In his words: I use 60/100 size glass beads. On a scale of 1 to 5, 1 being fine, 5 course, I use a 2.
I'm not sure what all of that means, but the results speak for themselves.
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.pbase.com%2Ftomfarr%2Fimage%2F68515485%2Flarge.jpg&hash=3f41ef915b6507b9c6de72d43862a88e8a20f8fc)
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.pbase.com%2Ftomfarr%2Fimage%2F68515491%2Flarge.jpg&hash=43369dcb89725f4d946da59198994c4e6ea8c622)
Yeah, I broke a bit if a fin in shipping, but I didn't let it bother me. It was on the bottom.
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I just had numerous parts blasted. My cylinder heads were done with glass beads and came out with a metallic looking finish, like Rob's above. The fork sliders were blasted with a fine sand before being powder coated. The sand left a dull gray finish. From my recent exerience I recommend a soft glass beads for cylinders heads and valve covers.
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When I had the T-bolt motor rebuilt, I asked about glass-beading engine parts. And my old Brit bike rebuilder guy said he didn't do it anymore. He said that no matter how much you clean the parts afterwords the glass bead "grit" remains on/in the metal which comes loose after you rebuild the engine and have it running. On the T-bolt cases we used a strong degreaser and and acid (muriatic I think) and a small brass brush and a lot of elbow grease (Provided by me). The case came out looking shiny and new.
This is worth about 2 cents.
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I tend toward using glass/silica beads on steel surfaces. Sometimes I'll use them on aluminum/alloy, but carefully and at relatively low pressure. The pictures of Rob Valdez' results on the work Bob Grauer did for him are typical of the finish using this method. My preference would be a little less of a peened look, but it's all personal. I use walnut shells on aluminum/alloy items that need cleaning/polishing rather than "resurfacing" or where I'm concerned about finish. Works great turning things like really gunked-up carburetors into near show quality.
Mark
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Rob,
I'm always a bit concerned when I see a head gasket surface that has been blasted to a coarse finish. My understanding, by way of others tutoring, is that the head and cylinder expand slightly differently and actually squirm about a bit on the copper head gasket. I had a head for another make of bike but the shiny head gasket surface had been blasted. I tossed it into the recycle barrel. Have you used the pictured heads? did they Werk ok? I'm curious.
rich
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From my days of racing bike engines, we would only use almond or wallnut media for the engine cases, sometimes the heads were done in glass beads, but usually not. Gasket surfaces were alyays machined. Fortunately I have still a lathe and a mill, so that is what i will be doing when I rebuild my R65LS in the near future. For now i have to work again for a quid, i build boats in China for a living so am away from home a lot.
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Rob,
I'm always a bit concerned when I see a head gasket surface that has been blasted to a coarse finish. My understanding, by way of others tutoring, is that the head and cylinder expand slightly differently and actually squirm about a bit on the copper head gasket. I had a head for another make of bike but the shiny head gasket surface had been blasted. I tossed it into the recycle barrel. Have you used the pictured heads? did they Werk ok? I'm curious.
rich
Two years, to be precise.
I installed them immediately after taking those pictures. I never gave a thought to the sealing surfaces, except for the time I asked Bob Grauer publicly on Boxerworks if he had checked the valve cover side for flatness, because my valve covers had never been so dry! And that was without center studs!
I did nothing for the head gasket except put in new ones on reassembly. No leaks there, either. /shrug?