Repainting crankcases

Watch out for:

Sandblasting or bead blasting.....whatever blasting media you choose, don't use one so abrasive as to cause a rough surface on the part. Regardless of how good you mask things up, blasting media will get in. Be prepared to clean, clean and clean. Any bearings left in while blasting, proceed with caution.

Powdercoating is fine on cases if that's what you want. Durable as anything but sometimes doesn't give the exact look some restorers are looking for. Works excellent over bare magnesium!! Extremely difficult to remove in the future. I'm sure the powdercoater guys have a chemical stripper that they are keeping secret.

Painting should be done with automotive grade urethane paints. Rattle cans do not provide good gas and chemical resistance. Been there , done that. Hate seeing paint rinse off a fresh motor first time the carb overflows. Epoxy primer on bare aluminum followed by paint. Some clutch covers and ignition covers are magnesium. If you use automotive paints over bare magnesium, the metal will gas / corrode under the finish. Will look like an ant farm trying to bust out before long. If you are going the paint route and wanting to use auto paint, have the mag pieces primed in powdercoat. Sand without breaking through and then paint. Auto paint stores can guide you on the products and the flattening bases required to get you the correct percentage of gloss you desire.

Hope this helps.

newmann,what about VHT case paint ? it says on the can chemical resistance and good to ? heat range.

I used some of that PJ-1 engine paint on one of my first vintage racers. Even pissed the wife off when I put the parts in the oven and stunk the house up! Carb puked and paint came off. The dirt that got on the cylinder fins pretty much cooked into the finish. Not a happy camper.

Did some horse trading to get one of my mini elsinores finished up and the guy that built the engine did a really nice job painting it up and assembling it. No idea what they painted it with but the first sign of gas from a vent hose and the paint was gone.

I have an engine I painted back in 1991 that still looks pretty nice and that thing was beat pretty damn hard for ten years straight.

I don't think heat is the big issue with paint on an engine. I do have a couple different aerosol satin blacks that I've gotten from some of my suppliers that I like to use and they seem to hold up pretty well . VHT? Not sure, but I'm open to any feedback you have trying it. My problem is that I'm surrounded by the good paint stuff at work!

Fresh 79 CR125 cylinder.



Glasurit single stage urethane with flattening base added. Not too flat, Not too shiny.

Some good aerosols here.

http://www.internationalepoxies.com/automotive_paints.htm

Used the semi gloss black enamel on this 77 RM125 silencer I cut apart, straightened and repacked. Talk about a waste of a full day!! Sure turned out nice though.

when i do my cases in the media blaster , at first they came out kinda rough , like newmann said but then i got a pressure regulator, and i can turn it down, then i can get any finish i want, for all i know a pressure reg, on a blast cabinet mite be common but when i bought mine from snap on it didnt have one,and yes the media gets everywhere, my cases go from blast cab, to blown off with air hose, to ultrasonic cleaner then blown off again after all holes are tapped, and all bearings should be removed before any of this nonsense begins

You could bolt it all together and blast it. Sounds like you are planning to paint the cylinders and heads as well. That's how this 83 CR250 engine was done.

If you are blasting an engine or parts that is going to remain bare, you need to be real selective of the blasting media you use. This old Hodaka engine was pretty well stained and discolored and was supposed to have somewhat of a semi polished look to it. Not your typical castings. Almost looked forged. There had been a repair done previously where the chain had thrown that had been rough finished that had to be cleaned up a bit. Ended up using a fine glass bead that cleaned the aluminum without giving it that sandblasted look. There are all different types of blast media from sand, aluminum oxide, walnut shells, baking soda, crushed glass, glass beads of different sizes.....the list goes on. Some can severely screw up your project.

Hey guys,

For what it's worth, I used that PJ1 engine paint on my 87 CR250 I rebuilt. I split the cases and mocked it back together again and sealed up the holes as well as I could before media blasting. Newmann is right, though, I don't think it is possible to keep the blasting media out of the bearings. I ended up replacing all the bearings anyway. It worked out though and the paint is holding up great. I know I spilled some gas on there and I didn't see any staining. Here it is after I finished the engine.



Although I painted the clutch and ignition covers, I ended up sending them to Dogger for powder coating to be more durable. He posts on here sometimes so you could message him. That dude is amazing at that type of work and I recommend you have him powder coat your cases. He has powder to match Honda's satin black or even the silver on newer CR engines and is very reasonably priced.

hey,your motor looks real good ! good job...

I've found Dupli-color's Truck and SUV paint holds up well to gasoline. I used it on one of my XR75 ignition covers. The bike has a leaky petcock and it's constantly dripping fuel on the cover, but the paint has held up perfectly.

I paintet my MotoVilla motor with VHT and I´m still happy with this paintjob after many races. but you have to follow the instructions on the can. friend of mine have done on his own, so the paint peel off.

Excuse me for butting in on this thread but I just really dig this kinda stuff.
I restored a dozen or so old bikes in the late 80s early 90s, and could have really benefited from internet information like this. Instead, I learned by mistakes or got lucky at times.
Some beautiful work here, newmann.

I'm still learning by mistakes!! Always looking for tips and tricks myself. Wishing Leeroy would share some in depth internal engine prep secrets......

Most of the bikes I build are with the intent on riding them so I usually don't go overboard on some of the intricate stuff such as misc. hardware. Occasionally I get carried away.

And don't ever discount the quality or skills of people who hang out here. Cylinder head and stud bolts courtesy of fellow vital member Tydog. I tried to return the favor, but this piece of work was F'n sweet.

COOL STUFF...

This is the stuff that I found that best matches OEM black on engine cases. Durable as all get out and resists chemicals. Make sure that you buy the correct primer for use with the epoxy paint.

Eastwood Extreme Chassis Paint

Some fine work here guys!

this is how it looks from start to almost finished.

Leeroy,
Could you tell me what grade/media you used to blast those cases....they look great! Also, what paint did you end up using and how are the results after use? Thanks!

Resurrecting old thread here....getting ready to paint my 81 rm250 cases, looks to be satin black, any new paint product recommendations? What you guys been using Lately?

Just did mine in ceracoat and couldn't be happier. Looks exactly like the OE finish and tougher than it ever was.
Did my last bike with VHT engine paint and it peeled off the sandblasted cases before I even started putting it together. Stripped that off and redid it with automotive epoxy and single stage polyurethane. It looks good but the gloss isn't correct and still chips easy compared to the ceracoat.
Downside to ceracoat is the need for extremely careful prep and somewhat special spray equipment (luckily a friend owned the recommended spray gun and I have access to a oven that won't lead to sleeping on the couch).

Rocky739, That came out nice...I wonder what the setup cost is for this....

I purchased a harbor freight blast cabinet and the recommend grit sand for it then I did a sample bottle of the gloss black from ceracoat.
Careful adhesion to the data sheet on prep and luckily I have access to all the rest of the needed equipment, booth, spray gun and oven.

Its good stuff, very chemical resistant, never had an issue with gas or oils or solvents harming it.