how to clean R75 aluminum engine block

[Unity]

TECH CORNER
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


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. )

[Bicyclist]

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.

[biometrics]

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.

Just my $0.02

-John

[ERC Scott]

That photo is of one of the nicest cafe racers I've seen. Would be really cool to ride...Scott

[Unity]

one of the nicest cafe racers I've seen.

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

--John

[Aether]

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.

[Bicyclist]

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.