Author Topic: Engine painting and stripping (Read 6152 times)

bimly · « **on:** June 06, 2011, 05:13:36 AM »

I'v got a 76' cb750 engine that runs ok, but has been painted with a broom and black paint with sand, crap etc in it by the previous owner. I don't really want to strip top and bottom ends to get the cases off as it runs fine. What has anybody else done to strip / clean up an assembled engine?
PS engine is out of frame, carbs off, drained, starter/ cases can all come off as need polishing and gaskets.

Hannibal Smith · « **Reply #1 on:** June 06, 2011, 07:47:20 AM »

You are going to want to keep everything "local", meaning it should be done incrementally.
I would start with a 50/50 concentration of Simple Green in a spray bottle, and start getting to the motor with a stiff brush. Spray, wait, scrub,spray, scrub etc. This method keeps everything in control, as you can do one section at a time.
You can also use paint stripper, but it needs to be kept local too, and I would also use a spray bottle to neutralize the stuff too.
You have a million nooks an crannys, and if you just attack it one section at a time, you will have a surprisingly clean motor.
Before you shoot the paint, I would go over the entire surface with a stainless steel brush (toothbrush size) in little circular motions, this will really help adhesion-and, it doesn't create all the sanding residue of paper.
Degrease with acetone etc. (I use paper towels) , then degrease again-
Shoot the paint. If you want it done right, it is going to take hours, and that is the fun of it!
This is just my opinion on how to best deal with the issue, it isn't as "correct" as full disassembly, but you can get amazing results if you are meticulous.

tlbranth · « **Reply #2 on:** June 06, 2011, 08:22:41 AM »

Hannibal's idea sounds pretty good. Years ago I painted the head and block while the thing was disassembled. I glass beaded it first. Those little bastards were everywhere and damn neart impossible to get out of the threads etc. Seems to me that an assembled engine would have less stuff to seal if you wanted to bead it - although a screwup in the sealing process wouldn't be good for the health of the engine. Let's know how you do. Post pics of your progress.

Greggo · « **Reply #3 on:** June 06, 2011, 08:27:05 AM »

Quote from: tlbranth on June 06, 2011, 08:22:41 AM

Those little bastards were everywhere and damn neart impossible to get out of the threads etc.

I've heard nothing good about using glass beads on the cases. Even the best prep job is not good enough to withstand those beads, and you don't want them in your engine.

I think Hannibal nailed it. Go slow, be careful, and it will come out well.

bimly · « **Reply #4 on:** June 06, 2011, 09:37:11 AM »

I'v dug a bit more and have been told that soda blasting can be done for about £80 - 100. Its water based, dissolves and does not micro pit alloy, if it gets into the engine it dissolves in oil or water and can be flushed out. Has any body tried this, I also hear it leaves such a fine finish that no painting is really needed (if the alloys ok underneath the crap!). Also as its power comes from is mico explosions as its energy is released when in contact with hard surfaces, it won't do in gaskets as they are not hard enough? - sound good option to me, even if I have to mask and paint after. Any experiences or comments?

Greggo · « **Reply #5 on:** June 06, 2011, 09:39:18 AM »

Many people recommend soda blasting for all those reasons.

sixthwisconsin · « **Reply #6 on:** June 06, 2011, 11:09:00 AM »

I soda blasted my head and cylinders after complete disassembly. It came out so nice that I didn't even paint them. I had a little sears sand blasting gun with a small hopper that I disconnected the hose from. I then took a 3 lb plastic coffee can and drilled a hole in the side at the bottom. After filling it up with baking soda, I have a soda blasting machine! Very simple, works great and is very easy. I did paint the lower case with VHT.

I can post pics tonight.

bimly · « **Reply #7 on:** June 06, 2011, 11:46:24 AM »

That would be good to see the end result. I'v bead blasted cases (stripped) in the past, and I know people have reservations, I would tend to agree it too several cycles of heating and flushing to get the stuff out, even thoug parts washed and air blasted! I understand the problem comes as the bead particles heat the surface on contact and get into the surface micro pores, then it cools and they get trapped. Yep, that's right heat the alloy in use and the pores re-open and hey presto crap in the engine. for engine parts NEVER AGAIN, but great for other bits. Horses for courses etc. Thats why I think soda might be the answer, but im still keen to investigate the stripper option if anybody has feed back good or bad?

camelman · « **Reply #8 on:** June 06, 2011, 01:56:12 PM »

I just went through thus on Saturday with a 400f engine. It took about two hours to completely strip the paint, and about two more hours for final prep and paint. I used a foaming engine degreaser from the auto store, and it removed all if the factory clear coat. The standard engine degreaser does not remove the paint, but the foaming one sure did. I then used a clean prep pad to sand off any remaining paint and sprayed the engine down with brakleen when done (bot environmentally friendly, but it washes off the surface without leaving residue).

To paint, I wasn't worried about the bottom of the oil pan, so I just propped the engine on the oil pan and a small paint can underneath the end of the oil filter housing. an hour later the last coat of engine enamel was drying. The paint looks great!!

Remember to wear a painting mask with hydrocarbon filtering capability. Long sleeves help out too!

Camelman

Helmet Hair · « **Reply #9 on:** June 06, 2011, 01:57:02 PM »

If you want to go soda blasting take a look this write up

http://www.aircooledtech.com/tools-on-the-cheap/soda_blaster/

sixthwisconsin · « **Reply #10 on:** June 06, 2011, 04:34:36 PM »

Here are pics of my soda blasted head and cylinders.

Blasting set up. Started with this smaller coffee can but ended up with a 3 lb can.

Painted the bottom end with VHT. I like the slight contrast between the raw cast aluminum and the painted lower.

chas · « **Reply #11 on:** June 06, 2011, 06:36:34 PM »

Stupid question. After soda blasting how do ensure no residue on the parts? Doesn't the dust go everywhere?

Charie

sixthwisconsin · « **Reply #12 on:** June 06, 2011, 06:44:35 PM »

I blasted out in the yard (freaked my neighbors out!) and simply washed the parts with hot water.

Graydude · « **Reply #13 on:** June 06, 2011, 07:00:58 PM »

Do you re use the media or just keep pouring a new box in the hopper? Did you do your frame with this process? Did it damage the top of the combustion chamber on your head? Mine 78 F3 needs lots of blasting and I'm just trying to figure our the best way.

sixthwisconsin · « **Reply #14 on:** June 06, 2011, 07:16:04 PM »

Frame was sand blasted and powder coated. I did not reclaim the baking soda, Its really cheap. No distortion of the aluminum with this process. It's really slick.

Maybe I'll start a soda blasting thread. Don't want to hijack this thread.

WarwickE36 · « **Reply #15 on:** June 06, 2011, 07:17:13 PM »

Hey sixthwisconsin... I dig your bike its very similar to my bike project... right down to the front turn signals... Where did you get your seat or did you make it?

A seat and an engine clean is basically my next 2 steps in the cafe process. Thanks for the help.

bimly · « **Reply #16 on:** June 07, 2011, 11:10:59 AM »

I'm in discussions with a mate with a BIG compressor, who was about to buy a home bead blast cabinet and gear. If this works could save both of us some cash! For a length of aquarium hose and £5 worth of soda its got to be worth a go. I think I may use the de greasing (foaming stuff) first as on another site a professional blaster said that parts had to be grease free and totally dry (which makes sense) first. It may also get some of the larger crap and paint off. Any body ever used demijohn bungs to plug up the inlet / outlets. Just a thought as I would think they are the same size. Also, has anybody who has soda blasted covered the kick start / clutch spindle / gear spindle prior to blasting to stop it getting in or for protection. I was thinking of putty? Thanks for the input guys. If I do this I willl post pictures of results to help others.

camelman · « **Reply #17 on:** June 07, 2011, 01:56:53 PM »

You might not need to soda blast at all if you use the same degreaser I used. It literally removed all of the paint with the exception of a couple minor spots I cleared up with a surface prep pad. I'll see if I can find info on it later today.

Camelman

tlbranth · « **Reply #18 on:** June 07, 2011, 07:44:52 PM »

What kind of degreaser is this? Sounds like something you wouldn't want to use on a car engine to clean it up.

bimly · « **Reply #19 on:** June 08, 2011, 01:34:31 AM »

Thanks camelman, if you could let me have a product name that would be great. Sound pretty serious stuff. Any effect on the alloy case itself or the polished side cases ?

Freaky1 · « **Reply #20 on:** June 08, 2011, 05:16:08 AM »

I'm in the process of stripping my motor and I had the shop strip the head and cylinder as part of their job, I'm not sure what they did but it was nice and clean. I've done some small parts with stripper, the brush on type, and some parts have been a real pain in the butt. Mostly finned pieces, such as the oil pan and oil filter cup, have not come out too well so I'm thinking about putting those in a glass bead blaster. For the cases I'm planning on stopping by the local car wash and using the spray on stripper, as I can imaging how difficult getting all the beads out would be. My dad has an old blaster kit, from Sears I think, that has a plastic jug for the media and I think I might go with the baking soda option if the spray stripper doesn't come clean. The different issue with mine is it's a black F motor and the factory stuff is pretty difficult to get off. In contrast the crappy high heat paint I used last summer comes off as soon as there is contact with the stripper, no need to wait even five minutes!

camelman · « **Reply #21 on:** June 08, 2011, 11:32:39 PM »

It's nothing serious, but somehow took the paint right off my engine. I can't vouch for what it will do to yours, but it is only $4 a can.

There didn't appear to be any issues from using it. The aluminum did not oxidize with all the white spots you get from using the wrong paint stripper (always use aircraft paint stripper, it is formulated to not cause flash oxidation of aluminum), and the seals are all in good shape wherever they protrude from the engine case.

I've attached a pic.

camelman · « **Reply #22 on:** June 08, 2011, 11:36:05 PM »

One other thing. If there are any stubborn spots between the fins, then go buy a pair of forceps from the auto store or wherever you find your forceps. They do a great job of holding surface prep pads to stick between the fins to scrub away stubborn dirt. I usually tear off a small piece and clamp it between the jaws. Then, I stick it between the fins and turn it sideways so it scrubs the upper and lower faces at the same time. Great results!

Camelman

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Author Topic: Engine painting and stripping (Read 6152 times)