If you beadblast/sandblast your motor, can you leave bare metal? Or do you need to spray with a high heat clear?

Thanks.

 

The problem with bare metal is rust. I had intended to leave mine to rust as i thought it looked cool. I still think so, but i paint mine.

I do not know how the external rust would affect the life of the cylinders and heads. It may be insignificant, but someone who knows would have to comment on that.

 

When the OP asks about bead blasting 'the motor' I assume he is referring to blasting the aluminum cases.
DO NOT bead blast any of the covers or primary cover unless you want these to be as dull as galvanized piece of metal.
Any surface you want to remain shiny you will need to cover with tape prior to blasting.

Likewise, and oil passage you want to keep clean will need to be plugged off or covered.
Glass beads will go everywhere and you do not want these inside the oil passages.

After the blasting the aluminum cases will look like they just came from the factory.
Leave them bare metal and 10 years later they will still look new, provided you do not get an oil leak and burn the oil into the pores of the metal.

Should that happen, it will be time to repeat the bead blast.

Of course any ferrous metal (heads and cylinders) can be bead blasted with the same result but these need a good coat of paint or they will rust the same day of the blast treatment.
pg

 

THank you sir. One friend has a 72 XLCH and his motor is all black, even the primary cover/gearbox. He said he blasted it with sand off the ground, (no joke), and it didn't have pits in the cover. Guy goes off-roading with his bike, haha.

If you advise against blasting the primary cover and such, what needs to be done, lightly scuffed, cleaned primed then painted?

Thanks.

 

Maybe I confused the issue here so let me try again......
If you have a black engine and want to repaint it black again you can bead blast the entire thing and cover nothing at all (on the outside of the engine). The bead blast will give the metal 'tooth' which makes the paint hold tightly.

What the OP was talking about was cleaning the aluminum by bead blasting and then his question was does he need to clearcoat it?

Bead blasting the aluminum cases gives it a slight pitting which looks just the way the metal cases came from the factory.....as cast aluminum. The metal contains no dirt in the pores.

The primary cover was also a cast piece at the factory.
When it popped out of the mold it looked just like the cases which is dull and rough.

But before the primary cover was installed on the brand new bike it went through a series of sanding and polishing steps to make it smooth and shiny....then it was installed.

If you bead blast a primary cover you will make it dull as was the original out of the mold.
The only way you can get it smooth and shiny again is go through the labor of sanding, then polishing the cover.

You do not want to do that, so protect the shiny surfaces with tape.
Look at many of the new Harley models. They will have dull primary covers and dull timing covers.
Some of them will have the engine painted black.

There are many people who like this look and for Harley it is far cheaper to leave the covers dull or paint them black rather than polish them.
Well, today that is not a polish surface but rather a chrome plated aluminum cover and I guarantee it costs the factory much more to do this than to rough finish or paint it.

Last of all.....Yeah, you could use sand off the ground, but not they way I would do it.

The material to use is glass beads and these beads come in a number of different grit sizes.
The finer the grit the finer the finish.
Sand is nothing but a crude material and leaves deep pitting in aluminum metal.
pg

 

Thanks PG for the information, very informative. I went to blast today, just did the heads. My sandblaster is having a few issues. I will get it painted tomorrow, and the motor back in the frame. Will show you all some pics in a new thread then

Thanks you.