Topic: Repainting an engine

[mjcarley]

Finally making some progress on my CB550 rebuild (don't buy a house in the middle of the process: when you have time you'll have no money and vice versa) and I am at the stage of rebuilding the engine into a better looking crankcase. Before I do I would like to repaint everything (the paint on it is flaking off). Any advice on preparation and materials, such as whether it is feasible to do the spraying myself? I am in the UK if that makes a difference to which products to use. I'm not bothered about absolute authenticity but I would like a reasonably tidy job.

[700504]

You have options, if you can order VHT paint then that's my recommendation. Degrease everything, use aircraft remover to get the old paint off and then go for it. You can choose to mask and paint the pieces individually or paint the whole thing after reassembly. I prefer to use VHT primer and then VHT top coat. I've had the best luck skipping the clear coat and just baking on the the top coat.

[martin99]

You won't get a decent chemical stripper off the shelf over here, the Health and Safety mob put a stop to that years ago, even previously trusted brands like Nitromors are now absolute crap. It won't even get through the old clear. Trades people can still get the proper stuff, if you know anyone in the paint or marine business who's willing to get it for you on account that might be a way around it. Sounds like you have the time but not too flush? Soda blasting is a good option, but expensive. It's usually priced per part, for example carb body twenty quid, alternator cover thirty quid, rocker cover thirty quid and so on. It all adds up. It is totally feasible to get good results yourself but as Cal says it needs a fair bit of elbow grease. I usually use wet and dry on the 'flatter' parts, for things like complex shapes and in between the fins a Dremel is your friend. I also use a brush to paint in between the fins as there is more chance of getting an even coverage than spraying. You can cure the parts yourself by getting a cheap used oven in your garage, or do it in the kitchen if you're single! There's also a thread on here somewhere where a fella made his own curing oven out of a foil-lined cardboard box and a heat gun - very inspirational for those of us who are a bit financially challenged! But to be honest, as someone who has been down this road several times before and not getting any younger, if (when!) the time comes to do the next one I think I would pay for prep at least, and forgo the dubious luxury of getting covered in crap for hours on end...

[gtmdriver]

On my Moto Guzzi engine I used POR15 Engine Enamel.

The engine was in bits so I degreased the casings, cleaned them with an acidic alloy cleaner, rinsed them thoroughly then used POR15 Metal Ready to Prepare them.

Brushing the paint on was not too successful as it left brush marks. Instead I thinned it slightly with white Spirit and sprayed it. The results were much better.

Before.



After



The paint also proved to be very durable resisting Oil, Petrol and Battery acid (Don't ask!)

[RAFster122s]

POR engine enamel is pretty thick because of high solids in the paint.  It goes on very nicely and unless it is hot it will flow out nicely most of the time.  Getting everything cleaned and prepped is the hardest part.  Dry everything very well before painting.  It will skin over easily overnight but it will take a week or more to dry properly in good drying conditions so it will not mar as easily when you are putting it in the frame and ding it.  It is like gtmdriver has said, very durable.  I used it on a car motor and once cured it was easy to clean up any oil spills or leaks and retained gloss for many years.  Never lost its gloss actually, but it was not exposed to a lot of sun like a motorcycle engine.  POR makes a good paint in my opinion.

[SOHC4 Cafe Racer Fan]

VHT works great but it's all in the prep.  After blasting, cleaning/scuffing, you need to thoroughly clean the motor with acetone (2-3 times).

Also best results for hardening the paint come from baking/curing the painted pieces.  If you cannot use an oven, you can fashion a make-shift hotbox with cardboard lined with aluminum heated via a heat gun.

[mjcarley]

I might go for soda blasting (I'm more flush than I used to be). The crankcase needs old paint removed, but most of the other  engine parts are polished and in quite a tidy state. Anyway, it's currently in the hands of my local auto engineering workshop to have the broken stud taken out.

A search for "aircraft paint stripper" on UK sites throws up some `interesting' products.

[GV1390]

VHT works great but it's all in the prep.  After blasting, cleaning/scuffing, you need to thoroughly clean the motor with acetone (2-3 times).

Also best results for hardening the paint come from baking/curing the painted pieces.  If you cannot use an oven, you can fashion a make-shift hotbox with cardboard lined with aluminum heated via a heat gun.

+1

I did this entire process twice. After blasting I cleaned/scuffed a TON with lots of acetone and the VHT high temp paint still flaked in certain areas. Be careful and tedious.

[Steve F]

Like they say, painting is 95% prep and 5% actual painting. I had my engine media blasted using plastic media.   It's NON ABRASIVE, and there's no dust created (other than the old paint coming off).  You must thoroughly degrease as best as you can with a good solvent like mineral spirits paint thinner before doing this.  I took the engine to a guy that specializes in this work and it came out beautiful!  Just prime and pain with your choice of paint.  I plugged up the intakes and exhaust with rubber stopper plugs and used duct tap on every thing else.  Masking tape will get ripped off easily with the blasting, so duct tape is required, and double up on it to be safe.
I would never use sand, glass beads or soda as this stuff get into every crack, nook and cranny and you have a major clean up before painting.  With the plastic media, a bit of compressed air and vacuuming is all you need.  I installed old covers that I really didn't care about before hand (valve cover, points cover, starter cover etc.).

[PeWe]

Soda blastiing kit, use your own compressor
http://www.ebay.co.uk/itm/NB-Hobby-Sodablasting-Gun-NB-Cleanblast-Blasting-Soda-5kg-NB-Glassblast-6-kg-/122294113221?hash=item1c794c13c5:g:~LgAAOSwQNRXLI4p

I have an old CB750 case I plan to fix. Have not tested it yet.

[SOHC4 Cafe Racer Fan]

As Steve F said, if you are even thinking of blasting an assembled engine, you better comprehensively mask with some durable material.  The abrasive particles will otherwise penetrate and get into your engine -- requiring a complete disassembly.  This can be risky.

[NobleHops]

I've lost track by now of how many folks I have pointed to this thread. I've done a similar process several times with very good results. All in the prep, etc. AND the heat cure.

http://www.cbxclub.com/forum/viewforum.php?f=27

[mjcarley]

So I've done the crankcase and am reasonably happy with it (not flawless by any means but I'm not trying to do a concours condition restoration). Paints are from RS Motorbike Paint (very clear instructions) and paint stripper (very effective) was Starchem Synstryp.

[SOHC4 Cafe Racer Fan]

So I've done the crankcase and am reasonably happy with it (not flawless by any means but I'm not trying to do a concours condition restoration). Paints are from RS Motorbike Paint (very clear instructions) and paint stripper (very effective) was Starchem Synstryp.

RS paints for bodywork are water-based.  Are the engine paints also water-based?  Do they have high temperature resistance?

[mjcarley]

The paints I used are definitely not water-based, and when I checked with RS if they were suitable for engine use (since they were selling me the colour matching the original Honda engine colour) they confirmed that they were suitable for the engine.

If this turns out not to be true, you'll be the second to be informed.

[NobleHops]

VHT works great but it's all in the prep.  After blasting, cleaning/scuffing, you need to thoroughly clean the motor with acetone (2-3 times).

Also best results for hardening the paint come from baking/curing the painted pieces.  If you cannot use an oven, you can fashion a make-shift hotbox with cardboard lined with aluminum heated via a heat gun.

+1

I did this entire process twice. After blasting I cleaned/scuffed a TON with lots of acetone and the VHT high temp paint still flaked in certain areas. Be careful and tedious.

Now I know why I am painting your crankcases today :-)

[SOHC4 Cafe Racer Fan]

VHT works great but it's all in the prep.  After blasting, cleaning/scuffing, you need to thoroughly clean the motor with acetone (2-3 times).

Also best results for hardening the paint come from baking/curing the painted pieces.  If you cannot use an oven, you can fashion a make-shift hotbox with cardboard lined with aluminum heated via a heat gun.

+1

I did this entire process twice. After blasting I cleaned/scuffed a TON with lots of acetone and the VHT high temp paint still flaked in certain areas. Be careful and tedious.

Now I know why I am painting your crankcases today :-)

+++++1

[GV1390]

VHT works great but it's all in the prep.  After blasting, cleaning/scuffing, you need to thoroughly clean the motor with acetone (2-3 times).

Also best results for hardening the paint come from baking/curing the painted pieces.  If you cannot use an oven, you can fashion a make-shift hotbox with cardboard lined with aluminum heated via a heat gun.

+1

I did this entire process twice. After blasting I cleaned/scuffed a TON with lots of acetone and the VHT high temp paint still flaked in certain areas. Be careful and tedious.

Now I know why I am painting your crankcases today :-)

Haha. Also to note, painting in the cold NY winter probably wasn't a good idea for the paint adhesion either.