bead blasting crank case? looking for advice and tips/

I have sandblasting equipment and have done that regularly. I have never glass beaded anything.

Rather than buy bead blast media myself, there is a place locally that rents glass bead blasting time at their cabinets by the minute at their facility.

I have a pair of bare crank cases that I want to get clean. Everything is removed from the crankcases. Was thinking glass bead blasting would do the trick and I could leave them bare after the bead blasting. Its the crank cases from a T500. There really aren't any passageways or areas to trap the beads. My biggest concern are the inside surfaces where the crank bearings, gear shift bearings, kickstart bearings, etc make contact with the crankcase covers. I would assume I don't want to bead blast these areas? If not, how do I protect them?

I was under the impression that glass bead blasting doesn't change the surface of the metal and you don't lose any metal material in the process? Maybe I am wrong? looking for advice on how to prep and blast these cases properly. Thanks.

ideally you don't want to blast any mating surface. That being said, depending on the media, psi, and blast setup, you can pretty much blast away with glass bead, although it can leave some tooth. There really isn't an issue unless you have an instance where something will need to seal on the surface, like oil seals. Two layers of duct tape or electrical tape will do the trick. Personally I see no benefit to blasting the inside of the case, you only run the risk of getting the media where you don't want it; or worse, embedding it in the aluminum only to have it come out later (rare, but it can happen). When I painted the cases for my kz1000 motor i masked the entire inside off, and it was a lot easier than trying to mask every individual surface.

Here is why I dont blast inside cases:

Take two similar pieces of aluminum that have approximately the same smooth surface that the inside of your engine has. Blast one really well, and leave the other surface as is.

Drip some oil on each piece. Tip each piece at a 45 degree angle and watch what happens. Oil does not move over a blasted surface nearly as easily. What this is going to do is reduce the rate of cooling and filtering, even if slighty. Personally I dont want my air cooled engines running any hotter.

As mentioned, glass will also embedd. Glass is very bad for engines.

The other reason is that to avoid blasting anywhere near bearing surfaces is a no brainer.

I think there is confusion in nomenclature here. There is a difference in glass bead and crushed glass media. Glass beads generally do not imbed themselves in the surface or leave a jagged tooth like other crushed glass does.

Glass bead is what I was referring to in original post. After some thought and reading these posts, i might ship them out for vapor blast

Re: bead blasting crank case? looking for advice and tips/

I had my cases blasted with plastic beads, which is the best option second to ice blasting, since both will not in any way remove or affect the alloy.
You can even blast straight onto bearing surfaces.
I was in awe with the raw cast finish it left, super happy.

I glass bead nearly anything without hesitation, but there are some things to consider that make a considerable difference.

The first thing to consider what the goal is. Aside from cleaning and paint preparation, often the goal is cosmetic. If you are going to paint, you can use nearly anything within reason and get a good result. Regardless of your goal, your parts need to be completely clean and grease and oil free before you blast. Everything that comes off your parts will contaminate the blast media, but also blasting (and even sandpapering) will drive some of the oil and grease into the surface. It may look great and clean, but that sort of contamination is very difficult to remove.

The quality of the media is very important. Glass beads are a lot more like little round spheres that peen the surface than sand or cut glass etc that actually cut into the surface. So new, pristine uncontaminated beads are capable of making an absolutely lovely smooth surface. The problem is that they degrade very quickly as they break from the impact and develop sharp cutting edges. I do a lot of carburetors, and if it is a set that I really need to look flawless - like new and not ever molested, I use brand new beads and don't overdo it. If the beads are new you can get the beautifully smooth dull polished look of a new die casting out of the tumbler. The surface shows no sign of holding oil or dirt and wipes smooth and clean. Once the beads degrade, the surface will become much rougher and "hold on" to oil as suggested by dohc. You can also use walnut shells, or any number of other kinds of media, but I think the heavier glass works better. I've never seen ice blasting myself. I keep several buckets of media in different stages of "wear" and select depending on the needed outcome.

Like I said, I blast most everything and have never had an issue - though I am not reckless. Never had an issue with any mating surface or bearing surface. Roller bearing mounting surfaces like in your Suzuki are steel, but I do cam bearings in aluminum heads and they are fine. And I have had enough of them back apart to have confidence they are!

I have never had an issue with glass beads after the fact, but I am serious about cleaning my parts after blasting them. If you are thorough and meticulous, it won't be a problem for you either, but forget an oil passageway and you will be crying. Your T500 has injector oil passageways for the main crank bearings. They will find glass media very unpleasant if you fail to clean the cases properly.

If you are going to paint your parts, any media will do unless you go super coarse and sharp like sand. If you want to leave them bare, you have to use brand new media to avoid a rough surface. Additionally, you will want to use coarse media. Yes, this is completely counter-intuitive, but large diameter media leaves (when new) the smoothest, shiniest most maintenance free surface. Sorry I can not remember the spec off the top of my head, but if your supplier has four bead sizes, get the largest. Just make sure they are actual glass beads. They will be expensive.

If you can not control your media, you will likely be happier painting afterward. Another possible choice if you do not want to paint is to send your parts out for vapor blasting, which is simply glass beading with water added to the air to propel the media. This can also create a rougher than you want surface depending on the quality control of the service, but seems to usually be a good option. I have seen good results but have not had it done myself so can not recommend anyone.

Here is a pic of some aluminum intake manifolds, the one done with some not new but not terribly worn beads. You can see the large beads leave a very nice smooth shiny surface. Click on the pic to enlarge and you will see the surface is not "grey" like you get with worn media. Brand new media looks even better.