Observations on cleaning engine parts

[mikenixon]

Okay, I admit it. I'm a little nutty about abrasive blasting, particularly glass beads. Sure, it's done all over and folks swear by it. But I just don't like it. Chalk it up to the dues I paid coming up in this business. I have witnessed horrendous outcomes from the stuff. Here then is my take on cleaning large engine parts.

A lot of folks think nothing of putting a cylinder head into a glass bead cabinet and blasting away. But, employment in numerous shops employing such cabinets including one which produced big inch Harleys, modded ZX11s and other exotica convinced me there just has to be a better way. Others dispute this, but it is near impossible in my experience to avoid the blasted abrasive's packing into blind holes, oil passages and places in the cylinder head or crankcase out of your vision that will later come loose and wreak havoc. I'm not lazy. I have cleaned like a fool and still observed media residue. Glass beads in particular seem to get a static electrical charge that makes them cling tenaciously inside oil passages and such, and no amount of air pressure, water pressure or what have you appears to help. Apparently, many get away with using this method but just know that it doesn't take long for retained abrasive to trash an engine.

My preference for engine and carburetor parts is ultrasonic cleaning and that is what I rely on today. It's also the choice of many engine builders, including friend and five-time Prostar national champion Nigel Patrick, who prefers using his 40-gallon ultrasonic rig for the Harleys and sportbike engines he builds. The result of ultrasonic approximates that of blasting, with the finish actually a lot more natural looking. And no abrasive media worry. As I say, preferable in my world.

Interestingly, the state of the art right now in engine cleaning appears to be dry ice blasting, which reportedly is the least surface altering of all and obviously (and to the point) the least invasive. However, atomizing dry ice apparently produces or leaves a toxic gas necessitating a hazmat suit. So this method, though ideal, isn't likely to trickle down to you and me very soon, and I have yet to see it advertised commercially.

Next downward on the desirability scale, and actually a pretty good choice, is soda blasting using specially made extra-coarse industrial soda. Soda is famous for powdering on impact, resulting in its instantly losing its abrasive quality and incidentally also making it one-time use. It's also inexpensive, leaves a very neutral finish, and best of all it is water-soluable. Soda does however require fairly high air pressure to be effective.

Next and more risky is wet blasting, misleadingly touted as "vapor honing", wherein traditional abrasive media is mixed with water, resulting in a slurry discharge. This combination has less tendancy to stick to the part due to the water's natural lubricative quality, and possibly also due to the interruption of the aforementioned static charge. I have some experience using it on carburetors. Wet blasting has suddenly become very popular due to the recent emergence of low-cost equipment. But don't lose sight of the fact that wet blasting is still old-school glass bead and aluminum oxide abrasive blasting, just with water added.

And finally, at the bottom, probably the oldest and certainly the least desirable in my view, the dry blast glass bead cabinet, sometimes used with aluminum oxide. This is an extremely harsh method and the resulting finish shows it. The media might as well be sand. Common for many decades now, dry blasting is beginning to fall out of favor with the emergence of superior methods. I simply shudder to think of this grit hiding in engine cavities, of which there are many in cylinder heads and crankcases.

Not mentioned in this list are the large commercial submerged-part "hot tanks", the revolving table caustic chemical spray cabinets, stainless steel sliver bombardment, and similar systems designed for serious industry applications. And even the methylene chloride dunk barrels with washing machine -like recirculating baskets once common in small shops; these last were very effective, if also neurological health hazards.

These are your choices. My money is on the ultrasonic method. And now you know why. Ride safe.

[pidjones]

In my career as a particle accelerator engineer and trainer, we used abrasive blasting due to the bare metal surface required. Fresh media and secure cabinets (major operational shutdown after someone snuck in after hours and blasted chain saw parts) were needed. I hated it because a) the cabinets, even with vacuum cleaner neg pressure always leaked a little abrasive dust that could contaminate moving equipment bearings, and b) I always seemed to develop respiratory infections after using them. Switching to aluminum oxide solved the respiratory problems - seems glass beads do the same as play sand, shattering on impact and creating glass dust that when inhaled lacerates tissues permiting infection to develop. To solve the other problem, the blast cabinet was discarded and a hand-held blaster used outdoors to clean the small parts before US cleaning in chloroform, acetone, then methanol. A final bake in 200 C oven for 24 hours prepared the parts for rapid assembly and installation in the high vacuum system.

Obviously a bit more critical than carb parts, but taught me a lot about cleaning parts. At home, I only use a hand blaster on the few parts that I blast clean (no carb parts), mainly for rust removal. I wear a good dust mask even then. Yes, the media is one-shot that way, but I've learned that garnet media cuts almost as good as black aluminum oxide, and a lot cheaper. I do have a small airbrush style blaster that has been used a few times. I have very fine aluminum oxide for it but it also works for very gentle cleaning with household baking soda. Very gentle, but sometimes you need to clean an area that can't be reached otherwise.

And of course the US. I now have the luxury of using surfactants that would have contaminated the parts at work. One that I use is Micro 90 - a lab cleaner that I obtained sample bottles of and because you use so little, still have a full bottle. A warning, though - it smells terrible. Really. Rinses clean, though.

I now only have a HF US cleaner. I don't recommend them. Ok for the small parts, but not enough power or volume for the bodies, and can't hold two bodies still joined by the garnish (to avoid the juggling of getting everything reconnected on throttle and choke shafts). I used to have a big, long laboratory US that would hold two GL1000 carb bodies (stripped) still joined by the garnish. But, it died after doing a CB750F set (individuals). The next time I rebuild a set, a new 10 liter US will be ordered. The last set was done by boiling, and I wasn't fully satisfied by it. I still had to used carb cleaner to get some passages clean.

[5speed]

I have a blasting cabinet with 120 grit aluminum oxide in it. I use it for my firearm refinishing hobby and have used it to clean up some motorcycle parts but I wouldn't dream of putting any engine,trans parts in it for the reason you mentioned Mike..
I also wear a respirator when I use it and my cabinet has a dust evacuation system.

[mikenixon]

Excellent and very informative (not to mention informed) comments, guys! Since going to ultrasonic about seven years ago I can't imagine doing without it.