Muckroot

XS650 Addict
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Hello all,

I have a 1975 XS-B that I am rebuilding, but unfortunately the case was unusable. Gary Hoos from Hoos racing (http://www.hoosracing.com) sent me a XS-J case for the cost of shipping. An absolute saint, I must say. Anyway, I decided to try and remove the black case paint from the XS-J case because I wanted to retain the classic bare aluminum look of the 1975 XS-B engine.

First I tried Aircraft chemical paint stripper, and while it did technically work it was slow, relatively expensive, and completely failed to strip 100% of the paint from the places a brass brush couldn't reach. So I decided to try soda blasting, because I had heard about it once on some completely unrelated forum (I think it was regarding removing gun finishes idk). I followed a 3 minute youtube video on how to make a sandblasting attachment for an air compressor, spent a whopping 10 dollars on parts: 7$ for the attachment components at harbor freight and 5 boxes of baking soda from the dollar store.

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I first tested the setup at 80 PSI on the old broken case to see if the blasting would ruin the gasket surfaces. I blasted the case-to-jug surface for a solid minute with direct spray and found that it had removed all the gunk, patina, and old gasket from the surface of the case without touching the aluminum itself. this seemed way too good to be true so I sacrificed the brand new polish on one of the rocker covers I did yesterday to see if the soda blasting would affect the polish noticeably. I figured even if it stripped the polish I could just rebuff the cover and it'd look good as new.

Long story short, the soda blasting at 80PSI does in fact microscopically pit the surface of the aluminum. it will remove the polish from buffed aluminum. BUT: this pitting (in my opinion) is so finite that it is not a factor in gasket seal integrity, and I'm willing to bet if gasket sealer paste is applied along with fresh gaskets on a soda blasted gasket surface it'll work better than the stock milled gasket surface. I fully intend to keep you guys updated in the long run and let you know if this engine produces leaks at high mileage due to this soda blasting process. I decided to intentionally soda blast the gasket surfaces on the case to get the most definitive results possible. Worst comes to worst I can always tear the engine apart and polish all the gasket surfaces with a Dremel and some Mother's mag and aluminum polish.

I settled on blasting 0-1 inches from the surface at 70PSI, both at oblique angles and straight on. crater shadow was a bit of a bummer, but not unmanageable. This is my second time blasting something.

Anyway, this is how far I got today, as well as how the soda blasted surface compares to the old non-painted case.

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And before anyone asks: Yes, I did use the proper PPE for this. the bandana was just for the initial test. I switched to a proper particle respirator and Saftey glasses when I started going to town on the XS-J case. Also, my mouth tasted like baking soda, so that was a bummer lol. I am happy to field questions.
 
Yup. That stuff is stubborn. Lather, rinse, repeat. Maybe even alternate between blasting and chemical stripping (Wally-World aircraft stripper is fine), just to get everything out of all the nooks and crannies. It all depends how picky you are about it. As for PPE, it's like an onion. The more layers, the better. If you have a respirator and goggles on, under a hood, you'll probably be all right. :twocents:
 
Another consideration I thought of as I was getting ready for college this morning is that regular sand blasting would leave sand particles all over the piece, and especially in any bearings that are still in the case. Not much of a consideration with a XS650 case as the only pressed in bearing is the shift fork bearing, and it doesn't see much use beyond when you shift gears. But on other engines this might mean every bearing in the engine is subjected to some amount of blasting medium. Baking soda dissolves in water and oil, however, so a good rinse with a power washer or even a hose should clear out 99% of the soda from the bearings, and after that it's a matter of reassembly and filling the engine with the proper oil. all the baking soda should either dissolve into the oil during the break in period and get flushed out by the first oil change or be ground up harmlessly by the bearings in the first 10 miles because it's so soft. Obviously I'd rather get it all out before reassembly, but it's another perk that makes rebuilding a little easier.
 
Couple things.... first, the roughened gasket surfaces will seal just fine. Over the years I've assembled many engines that have been bead blasted. It's never been a problem.
Baking soda dissolves in water and oil, however, so a good rinse with a power washer or even a hose should clear out 99% of the soda from the bearings,
My concern isn't the soda, it's the materiel being blasted. Paint chips and dirt grit blasted loose and into an oil passageway could very easily block it and would be pretty hard to remove. I'd highly recommend blocking off all oil passages.
 
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I'd highly recommend blocking off all oil passages.

Excellent suggestion! I'll make sure to be very thorough about cleaning out everything with little pipe cleaners and carb cleaner, but I wouldn't have thought to block off the oil passages entirely. Are there any in particular that are either really tight or relatively long that I should pay extra attention to?
 
I posted some information on my face book page.

Hooser that was great info! I watched your video where you have the top case in a big tub and are flushing what looks like radiator cleaner through the oil passages. how did you go about doing that? I have a big ol' tub ready to go, and plenty of oil or cleaner or whatever works best for flushing the passages. I'm guessing you got a little garden pond pump and hooked it up somehow?

Oh, and the top case is ready to be flushed. with the straw attachment I've been back spraying carb cleaner through the little oil holes I can find using the diagram, and I haven't had any give me sass yet.
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UPDATE:
Finally finished soda blasting the case that Gary Hoos sent my way. pretty pleased with the outcome. here's what the two halves look like.
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It took a looooot of baking soda, but luckily for me the boxed stuff at the dollar store is CHEAP! these make up about half the boxes I used total.
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After power washing all the baking soda out of the two halves I back flushed all the oil passages with carb cleaner. then I hooked up a cheapo drill pump to the port where the oil pump feeds oil into the oil passages and ran some oil through them. The pump wasn't as strong as I would have liked but I feel like it got the job done. All the oil passages seem to be in tip top shape and flowing freely.

Also received the parts I'd ordered! Did the new part's dance, and got to work assembling the transmission.
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If you'd like to follow along with this build I post updates to instagram (Muckroute). I am also keeping a detailed log of everything I buy for this build; down to the cotter pins. I'll make a post about that at some point once I hit a major milestone if anyone is interested.
 

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