Engine sandblasting

N

NowhereFast

New Member
So I got my cb750k dohc engine out of the frame and looking extra shitty, i plan on sandblasting it just because i think that will be the quickest most effective way of stripping it of the old paint and whatever else coat's the engine. Question is though what is the BEST way to plug up all the holes intake, exhaust, the 2 opening's on top of the case 1 of which connects to the oil dipstick. Anyways i was thinking tape at first but even with being super careful sandblasting i don't trust it. Any ideas?

P.S does the cheap Engine Enamel paint you can buy at advanced auto hold up any good?
 
Rubber hole plugs, from any hardware store. They're cheap and will actually keep material out of your engine. As far as SAND blasting your engine. STOP!!! You don't want to use sand, at all, ever... Baking soda, walnut shells, liquid blasting, sure, go right ahead. SAND media is like asking for scored cylinder walls and plugged up oil passages, even with the rubber plugs.

As far as the engine enamel at the local parts house, as long as it has ceramic in it, it should be fine. I've got 2 coats of the 1100* engine enamel on my cases and they don't show any signs of peeling or fading.
 
sand blasting an assembled motor is extremely risky.

I would suggest aircraft paint stripper and then rinsed and dried, then soda blast.

I intend to try the conical rubber stopper/plug things you can get at hardware stores and then a bead of silicone around them after tapping them into the holes when I attempt something similar.

sand as a blast media is really harsh and will rip into the aluminum really quickly.

Glass bead or walnut shell will leave a better paint ready finish, but the risk of getting some media inside the motor is too great even with these.

soda or dry ice blasting seem to be the only viable options, and even then you need to be paranoid.
 
+100 for soda blasting vs. sand or beads.

Explore the option of vapor blasting too. But bottom line is the best and 'right' thing to do when cleaning up / painting an engine is to take it apart, blast the cases, paint them on their own baking the finish on and then reassemble the engine with new seals and gaskets.

If you're going to blast it, remove it from the frame and seal everything up tight then soda-blast it. I'd leave it raw aluminum at that point if it were me.

Is this a black CB750F engine?
 
Tim said:
+100 for soda blasting vs. sand or beads.

Explore the option of vapor blasting too. But bottom line is the best and 'right' thing to do when cleaning up / painting an engine is to take it apart, blast the cases, paint them on their own baking the finish on and then reassemble the engine with new seals and gaskets.

If you're going to blast it, remove it from the frame and seal everything up tight then soda-blast it. I'd leave it raw aluminum at that point if it were me.

Is this a black CB750F engine?
Click to expand...

Tim I've got someone that's going to vapour blast my cases and carbs for me on the cheap. All will be stripped down totally and I was wondering what the finish is like and if it will be ok to leave them raw?

I'm worried about them staying that way, won't they stain easier or mark?

Essentially: leave natural or VHT paint?
 
Aside from vapor or dry-ice, I would not risk it. Blasting media seems to get in no matter what precautions are taken. If you just want to freshen the looks of the engine with a new coat of paint, give it a thurough degreasing, first something cheap like kerosene, or mineral spirits. Then scuff every inch of it with sandpaper or scotch-brite. If there is oxidation, a fine wire wheel in a hand drill works fine. Then another wash down with some Simple-green or Purple-power type product. Last thing I do before paint is a wipe down with something that leaves no residue... rubbing alcohol, the 90% isopropal.
I've had good luck with Duplicolors Engine paint when the engine is prepped this way. I use their 1650 aluminum and the match to cast aluminum is great.
Here is my GL...

And My Zooks

My most recent DOHC CB's like yours
 
I would not blast a motor with anything other than vapor. Wonder how that Duplicolor engine paint holds up to gasoline?
 
I use soda blasting after thorough degreasing but the dry ice blasting can work. The soda blasting leaves a nice texture for the primer to bite into. I find the dry ice to be a little slick. It comes from stripping molds of mold release and it can't alter the texturing. You want the texturing of the blast media for painting.

I really hate paint but if you use, primer, paint and 2K clear its a 80% solution. I am going to try POR15 on my next black engine with a top coat and 2K clear. The POR15 will stand up to anything and is black (but not UV stable so it needs a top coat). That way if the black gets a few chips, the POR15 will hide the fact.
 
neevo said:
Tim I've got someone that's going to vapour blast my cases and carbs for me on the cheap. All will be stripped down totally and I was wondering what the finish is like and if it will be ok to leave them raw?

I'm worried about them staying that way, won't they stain easier or mark?

Essentially: leave natural or VHT paint?
Click to expand...

I've heard great things about vapor blasting and that you really don't need to paint after.

Google images of it and read up on it - I'd leave it natural for sure.
 
I just did a bunch of parts using my HF blast cabinet. Soda works great for general cleanup and minor corrosion removal. Aluminum oxide works great for thick paint removal and major corrosion removal.

I bought my soda at HF and it's held up to multiple blasting sessions without breaking down.
 
I've got a well sealed '75 Honda XL 250 engine.... I REALLY don't want to go into a full engine rebuild especially since the engine doesn't leak and runs like a dream. Just more than I wanted to get into... but the engine was caked in gunk from years of chain lube and spilling oil on it. I did a thorough cleaning done using gunk, brushes, and picks - finally got it pretty clean but it still just doesn't have a nice finish from years of corrosion, water, and such. I looked into dry ice blasting but it is so hard to come by and from what I can tell quite pricey.

That pretty much leaves soda blasting or walnuts.... I just don't know which? Also, I can't seem to find any vapor blasting other than a guy in Oregon who only takes small disassembled parts. If I seal up the engine ports really well and then do a full oil flush with some marvels mystery oil as soon as I get it back on the bike do you think I'll be safe?

Thoughts? Ideas?
 
Thanks for the info everyone, I'm at the same place with my build and anxious to get a great looking motor.

I have heard that the paint stripper option is a really good one, and pretty inexpensive as well. Does anyone have any recommendations on paint strippers?

Here's my build thread... 1982 HOnda CM450 with a single swing arm!
http://www.dotheton.com/forum/index.php?topic=55387.msg633359#msg633359

Thanks,
Jared
 
MatthiasSalzburg said:
I just did a bunch of parts using my HF blast cabinet. Soda works great for general cleanup and minor corrosion removal. Aluminum oxide works great for thick paint removal and major corrosion removal.

I bought my soda at HF and it's held up to multiple blasting sessions without breaking down.
Click to expand...

Also harbor freight has a sandblast gun for about 20 bones...


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