Cleaning and painting engine cases.

So what's the best technique for bringing old cases back to factory finish ?

About painting the cases, wouldn't the paint aid the engine in retaining heat ? What's the benefit of painting cases ? What kind if any paint sticks to the aluminum cases and doesn't start flaking off after a couple rides ?

Almost all motorcycle engines are 'painted'. Some get black, some silver, some clear. The paint is there to prevent oxidation.

When repainting a bike engine, there are three steps:
1) Prep. Cleaning the engine and roughing up the surface to allow the primer to stick. This involved soda or walnut shell blasting, sanding, wire brushing, sticks with steel wool, and about 20 other possible methods. I like soda blasting and then 600 grit sand paper wrapped around a Popsicle stick.
2) Primer. This is the coating that actually adheres to the aluminum. I don't have any brand names for you, but get a primer that is 'high temp' so that it does burn off. Note that aluminum 'rusts' instantly on contact with the air, but creates a barrier that prevents future oxidation. The primer you use needs to be formulated for that.
3) Color. Pick your engine color and use the high temp version of that. You may need to 'bake' the parts, depending on the paint you choose.

Believe it or not, the best source for 'rattle can' versions of all of these (locally for me) is AutoZone. Your retailers will vary. Most paint shops know how to paint hot aluminum, so getting it done professionally shouldn't be that big a deal. There was a thread on here just a couple days ago where someone showed their progress in repainting their engine.

Here's an excerpt from Pit Stop Peformance (Joe Hooper)
www.pitstopperformance.com/

Refinishing

Pit Stop Performance head, cylinder and case refinishing procedure.
The following is the procedure followed for refinishing cast exterior engine parts.
The procedure as written is to apply a silver finish to the parts.
The procedure can also be used to apply a flat black engine finish (1973 Z1)
or the semi gloss engine finish (1978 Z1R).
The only change is the paint that is applied.
The parts are first cleaned thoroughly to remove any grease, dirt and oil.
Following cleaning, all holes are blown out with compressed air.
In preparation for glass beading, all of the threaded holes must have bolts installed.
This is to keep glass beads from being packed into the holes.
It will not prevent glass beads from entering the holes, but it will prevent
a large quantity from entering the threaded holes.
Next the part is bead blasted using a coarse abrasive.
I use Skat Magic which leaves a pretty rough finish.
This will remove what is left of the factory paint and provide a
clean porous surface for painting.
Next all the bolts are removed and the part is solvent cleaned again.
While in the cleaning solvent, a tap (the correct size for each thread) is run into each
threaded hole.
This will loosen any glass beads which entered the holes, as well as clean up any
damaged threads.
Following the thread chasing, WD40 is used with a tube on the nozzle to clean out
the threaded holes.
Push the tube all the way to the bottom of the holes several times to completely
clean out the holes.
Continue cleaning with solvent to remove all traces of the WD40.
When the solvent cleaning is finished, remove the solvent using soapy water.
I like to use Dawn dishwashing detergent.
It cuts grease and oil well.
Once this is complete, the part should be rinsed with water.
Finally, the part is dried using compressed air.
Each threaded hole should be blown out.
A thin blower extension should be used so that the compressed air can be introduced
at the bottom of the threaded holes.
That way the loose material can be forced out the holes from the bottom.
Once this cleaning is complete, the part is ready for painting.
Heat the part to 450-500 degrees Fahrenheit,
I use a gas grill with a thermometer.
While still hot, apply Harley Davidson high temperature silver paint
(part number 98660-78) if the finish is to be silver.
This is very critical.
By applying the paint hot, the adhesion is vastly improved.
This coat of paint will look similar to a glass beaded surface, it will retain a porous
appearance.
Allow the part to cool to room temperature.
The second coat of paint is applied at room temperature.
This application will give you the shiny deep silver finish that you desire.
Allow 24 hours to pass.
Finally, heat the part to 250-300 degrees Fahrenheit for one hour minimum.
This final step will cure the paint and toughen it.
After the part cools, it is ready for assembly.

Note the extreme care involved to assure removing all traces of glass bead media.

Good Fortune!

Alright, given the great knowledge you guys have shared about cleaning and painting the engine cases how does one go about keeping the paint out of unwanted areas ? Can't tape over the areas because when you heat the block it'll cook the tape off. Install covers and paint over them, then clean later ?

I personally sandblast mine then polish them.

The only motors I ever coated were KZ900/KZ1000's, KZ750/4's, and oil cooled GSXR's. I will go along with the glass beading and the cleaning part. Now I used good duct tape and taped up ALL the gasket surfaces when I had the cases blasted. I did my own glass beading at my local friendly machine shop. I always bolted the cases back together with EVERY case bolt when I blasted them. The block, cylinder head I duct taped up too. The engine covers I did not tape up. Blast everything. Then take it all apart again, and clean, and clean, and clean to get all the glass bead out. Then reassemble the cases with every bolt and torque them to factory specs and you are ready to paint. You don't want to be assembling your motor and find out you have glass bead in some bolt holes!!! I threaded a bolt into EVERY threaded hole there was on my cases and cylinder heads before I coated them.

Now the only coatings I ever sprayed were Kal-Gard Gun Kote, and their KG-9600 color coatings. Gun- Kote is that matt grayish/ black finish that came on all the oil-cooled GSXR motors, and what Yoshimura coated all their GS1000 Superbike motors in. Now that 450-500 degrees for just painting is extreme in my book. I always used 175~200 degrees. Your cylinder sleeves might fall out too at that higher temperature. That way your duct tape also stays in place at that lower temperature. The first coat of Gun-Kote got sucked right into the glass beaded metal, and you see no color until you went back over the same area a few minutes later. Paint all the parts before they cool. For all the Kal-Gard coatings I used only 300 degrees for one hour to bake them.

Take them out of oven and let them cool naturally. DON'T blast them with air to cool them quicker. My welder extraordinaire told me to wrap them in blankets, and let them cool. The duct tape comes off, but you will have all kinds of gummy adhesive left on the gasket areas. A little carb cleaner on a shop rag takes all of it right off. My Kz1000 Superbike motors have been torn down, washed in Safety-Kleen, and reassembled 15 to 20 times. NONE of the coating ever came off. I think if your use a good brand of engine paint, glass bead and clean all the motor parts that finish should be as durable as the factory finish.

I used my home oven to bake all my motor parts for years. Your first couple of pizza's taste a bit funny after you bake your motor parts, but after a while that taste goes away!!!

If I had the time/money I'd have everything vapor blasted.

guitargeek wrote: If I had the time/money I'd have everything vapor blasted.
. . .

If that's vapor blasted --- sign me up!

Good Fortune!

I have never heard of vapor blasting, so i looked it up and it looks like it would be a good option. I wouldnt mind owning one.

Powerstroke_fan wrote: I have never heard of vapor blasting, so i looked it up and it looks like it would be a good option. I wouldnt mind owning one.

A buddy of mine owns a VB rig, but he's all the way up in Rhode Island.

wonder what kind of prices those run for a smaller cabinet?

That's awesome info Dr.Gamma !!