how to clean R75 aluminum engine block

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how to clean R75 aluminum engine block

Postby Unity » Thu Aug 22, 2013 5:19 pm

Motorcycle Classics Blogs wrote:
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Technical Q and A for classic motorcycle maintenance and repair.

Clean Aluminum Engine Block on BMW R75
6/5/2013 11:36:50 AM
by Keith Fellenstein

Image
Motorcycle Classics Project BMW referenced below.

Q: I have a 1977 BMW R75/7 and am trying to clean the aluminum engine block to bring it back to a newer looking condition. I thought you guys may know of a product to recommend to enable me to do this? I ask as I saw the BMW you restored. My R75/7 is in much better condition than the one you restored. The bike I have was inherited from my dad. He bought it new in 1977 and it has only 37,000km on it! — John/via email

A: Several readers emailed to ask about cleaning the aluminum engine casings on our project BMW. Editor-in-chief Richard Backus did that task himself. Richard says he used a variety of techniques, some more useful than others. He tried steam cleaning, which worked well enough a couple of projects back on the Honda 500 but did not work on the BMW. He also tried several solvent based products, but reported that the best results came from using Simple Green soap, a scrub brush and elbow grease.

--MC

--John
(Sorry if it wasn't what you were wishing. :()
2002 R1150RT, Silver
Silver, the "cool and aloof" color.
(Road & Track Vol. 56, No.2, p. 19)

1971 Triumph Bonneville, Gold
Gold, the "paying the restorer" color.
(Trust me.)
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Re: how to clean R75 aluminum engine block

Postby Bicyclist » Thu Aug 22, 2013 8:31 pm

I know a guy who has had good results with walnut shell blasting his Triumph cases. I've never used walnut shell, but have glass bead blasted my valve covers and cylinder heads. Lately, I've been using straight Pine Sol and a nylon brush with good results.
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Re: how to clean R75 aluminum engine block

Postby biometrics » Fri Aug 23, 2013 10:54 am

Crushed walnut shells are often used as a tumbling medium for empty ammunition brass to clean it up prior to reloading. It is abrasive in nature. Not sure I would want to use it on the outside of an engine casing, unless some form of final finish were to be applied after cleaning. I think the raw aluminum surface would be even more susceptible to corrosion and stains after using any abrasive cleaning method. A high temperature "clear coat" would be ideal, but I don't know that one even exists. Perhaps hi-temperature silver engine paint might be the answer after cleaning takes place.

Pine Sol is known to remove even the most serious of engine deposits on manifolds, carbureators, and throttle bodies just by soaking in a strong solution of it. I have used it myself on the quad carb assembies on my previous 1983 Honda Nighthawk with absolutely great results. I am not so sure how well it would work on long term Stains in the aluminum.

Elbow grease will definitely be required regardless of the method used. :lol:

Just my $0.02

-John
1983 R100 /T with Velorex Sidecar
2000 K1200LT (Sold!)
1999 R1100RT-P (Sold!)
1983 Honda Nighthawk 650 (Sold!)
1973 Yamaha 125 Enduro (Ripped off!)
My Avatar? U.S. Army - Kagnew Station, Asmara, Eritrea, East Africa, 1972-1973
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Re: how to clean R75 aluminum engine block

Postby ERC Scott » Fri Aug 23, 2013 2:58 pm

That photo is of one of the nicest cafe racers I've seen. Would be really cool to ride...Scott
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Re: how to clean R75 aluminum engine block

Postby Unity » Fri Aug 23, 2013 3:32 pm

ERC Scott wrote:one of the nicest cafe racers I've seen.

Yes, I was happy to bring it back around. :D
http://www.bmwbmw.org/forums/viewtopic.php?f=13&t=20222&p=266213

--John
2002 R1150RT, Silver
Silver, the "cool and aloof" color.
(Road & Track Vol. 56, No.2, p. 19)

1971 Triumph Bonneville, Gold
Gold, the "paying the restorer" color.
(Trust me.)
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Re: how to clean R75 aluminum engine block

Postby Aether » Fri Aug 23, 2013 3:34 pm

I saw more than a few recommendations for WD40 with Scotch Brite Pad. I've tried it and had decent results - not factory new, but significant in grunge removal with the added benefit of the WD40 leaving a coating on the surface that prevents further corrosion and staining.
-Adam

2014 Triumph Street Triple R (3 Cylinder LandJet)
1976 BMW R75/6 (2 cylinder/2 wheel fun)
1966 BMW R60/2 - R75 Conversion w/ Sidecar (2 cylinder/3 wheel fun)
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Re: how to clean R75 aluminum engine block

Postby Bicyclist » Fri Aug 23, 2013 9:13 pm

biometrics wrote:Crushed walnut shells are often used as a tumbling medium for empty ammunition brass to clean it up prior to reloading. It is abrasive in nature. Not sure I would want to use it on the outside of an engine casing, unless some form of final finish were to be applied after cleaning.


Well, the airhead engine case is raw aluminum to begin with. Walnut shell is gently abrasive, not like sand, for instance. As I said, a friend has used it with good results on his old Triumph.
George

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