Topic: 69 cb750 engine restoration

[ianglean]

I would like to spruce up my 69 cb750 engine. I was hoping that I can keep it "silver" since that nice engine will pop out but I am open to powder coating it black as well. How would you go about in doing it after stripping the internals?

1.   Sand blast, polish, possible clear coat (want to keep it shiny for a while). Is there a type of clear coat I should use?
2.   Sand blast, powder coat
3.   Sand blast and polish
4.   Or just polish ( I believe some parts may be clear coated so apply paint stripper?)

are there parts of the engine that should not be powder coated or clear coated?

Pics in this thread
http://forums.sohc4.net/index.php/topic,157312.msg1802845.html#msg1802845

[Don R]

 I'd check into soda blasting or dry ice blasting, most blasting is unkind to aluminum. Experts will arrive shortly.

[Powderman]

If you want to powder coat it, media blasting is a necessary step for durability and longevity. The trick is finding a competent blaster. Many think just shooting sand out a of a pressurized hose is all you need to know, that's how parts are damaged. I use Black Diamond Coal Slag for blasting  and many steps to clean the cases after blasting. If this is the direction you are contemplating make sure you put the cases in an oven at 375°-400° for 45-60 minutes to outgas them before blasting them or you will have issues with bubbles in the finish when you coat them

[calj737]

choose Vapor Blasting to achieve the ultimate appearance- http://www.restocycle.com

Nils (Noblehops) is a member here and produces the most beautiful results. The cases will still oxidize slightly as the finish is not permanent. But treating it and maintaining it are not unduly difficult.

I'd steer clear of black powder coat simply for the aesthetic, unless you're planning a non-stock build. I do recommend powder coat, but the vapor blast is luxurious!!!

[CycleRanger]

I'd check into soda blasting or dry ice blasting, most blasting is unkind (to say the least) to aluminum. Experts will arrive shortly.

This!
imho, don't go near the engine with sand/beads, etc.

[Bodi]

Grit blasting means a LOT of cleaning but it isn't out of the question. I would go with what Powderman says. Probably the surface needs to have enough texture to hold powder properly. Soda or vapor blasting are best if you don't want much or any damage to the surface, really excellent for paint removal from aluminum or fiberglass.

[CycleRanger]

Grit blasting means a LOT of cleaning but it isn't out of the question.

It also means possible damage to bearing surfaces.

[ianglean]

I have to check with our local sand blaster and hopefully they have other media that they can use. We have very limited resources here where I live but I was just planning to blast the exterior part of the engine. I am gearing towards a not stock build since cb750’s here is hard to find. Practically I am just saving the frame, engine and tank.

Been reading online that soda and corn can be used as media. Can we use just regular baking soda and is this just ground up corn? How much medium is needed to blast one engine? I am thinking I can get the media and bring it to the shop for them to use?

I would love to hear tips if I just polish the engine. Which part can I clear coat for should I just keep it as is without the clear?

[calj737]

Soda blasting is not exactly the same media as your wife uses in the kitchen. The industrial product is a one time use, and its more coarse so it doesn't clog. Humidity there (Philippines) will be the greatest challenge for soda as it will absorb the moisture in the air and not flow as well. And the equipment differs slightly from regular blasting, but can be adapted.

If you want to polish the cases or covers, prepare yourself for hours of sanding in varying degrees of grit, and then more hours of buffing working through the polishing rouges. Any aluminum left untreated will oxidize. The rate and decay will depend entirely upon how you maintain it and what weather exposure it gets.

[ianglean]

Thanks for the tips. I guess I've been watching too many diy videos. Lol