Engine paint?

[Packer]

The older generation of bikes, including BMW airheads, didn't have painted crankcases so why do newer bikes like my 1150?

Is it because a different alloy is used these days? Is it essential to have this type of alloy painted?

I had noticed corrosion on the sub frame and some patches of blistered paint on the gearbox and front cover so a bit of a refurbishment seemed to be indicated. However, the more bits I take off the worse it all appears to be I now have an engine and transmission propped up on blocks of wood and piles of bits all over the garage.

Where the engine paint is blistered I find black gunge underneath it. As the bike is mechanically very good I don't want to dismantle the engine and tranny, what's the best way to clean it up? I have the front cover off the engine at the moment which looks to have been a mistake as the inside is now exposed to debris. I may need to put it back temporarily whilst I clean off the old paint.

Where the paint on the bell housing, gearbox, swingarm and final drive is blistered large patches just flake off and there is white powder underneath it. I'm assuming that the corrosion just works along under the paint. Is this because BMW didn't use the correct or best primer?

Lastly, has anyone used Hammerite Smoothrite on the engine crankcases? Does it stand up to the heat OK or do I need to get a special high temperature paint for those parts?

 

[gwigglesworth]

Hammerite is horrible stuff and will make a very thick coat.

I have repainted many engines using stove enamel or black engine paint from the local paint shop.

Black engine paint like hammerite can make a very thick layer which looks great on cars but not so great on bikes.. Engine paint can be used on bikes but many many thin layers! I.e. take your time.

 

[D6]

a lot of engines have a high magnesium content in them, painting is needed as the alloy wont last as long without,
look at 90,s suzuki/yam spoked wheels, a lot have white stuff flaking off

 

[stephen.stallebrass]

Engine cover Repair and repaint....

Take a look at how this guy repaired and repainted his R1200GS engine cover.

 

[roddy]

Hammerite Smoothrite on the engine crankcases? Does it stand up to the heat OK or do I need to get a special high temperature paint for those parts?

on the tin of this stuff it does state not to use in areas that regularly reach 80'C, whic mean it may not have a bit of flex in it so unless they do a high heat smoothrite, I'd be cautious about using the normal stuff.

 

[D6]

iv used normal spray on smoothright on jap engine casings, its never come off,,and i recon a 4cyl runs hotter than my old bm,
wouldnt use it on cylinders though

 

[MikeP]

Where the paint on the bell housing, gearbox, swingarm and final drive is blistered large patches just flake off and there is white powder underneath it. I'm assuming that the corrosion just works along under the paint. Is this because BMW didn't use the correct or best primer?

The white stuff is the oxidisation of the aluminium that occurs when it is exposed to moisture (and made worse by road-salt). It goes to the point of your question regarding the absence of painted engines on older Boxers: They used to suffer from the same process. The difference being that normal washing removed the worst effects whereas the later, coated finish, protects the casings up to the point where the coating itself is compromised.

It may look as though the coating is intact but scratches and splits allow the corrosion to work away beneath the surface.

The engine and gearbox cases are painted, the swing-arm and final drive housings are powder-coated. The latter suffer badly because like the fork-brace, they are powder coated and then some surfaces are machined to remove the coating. This leaves an edge where the coating is prone to moisture getting under. Have a look at most 1100/1150's and you'll see that the coating starts to lift at these points.

Lastly, has anyone used Hammerite Smoothrite on the engine crankcases? Does it stand up to the heat OK or do I need to get a special high temperature paint for those parts?

Yes. I've used Hammerite on engine casings without any adverse effects and I've tried some so-called VHT-engine paints. Tuff-n-Touch is one that I've used. It's no better than Hammerite but a lot more expensive.

Unlike some claims, Hammerite doesn't leave a thick coat unless it's applied thickly.

Stove enamel is good but requires oven-curing. Hammerite is an enamel and is heat-resistant (up to a point; don't try using it on exhaust headers for example).

I've used it on 2-valve Boxers,

and my 1150,

This is Tuff-n-Touch used on my K75,

If you opt for Hammerite, once it's all back together, run the bike for a short time to get some heat into the paint before you go for a ride and get it really hot and the finish will cure better. The first time, you may be alarmed by the smell of the paint as the engine warms-up. Allow it to cool (to fully cold) and repeat until you cannot smell the paint and then you'll know that it's cured nicely.

A decent hot-air gun will help to cure the Hammerite on none-heat affected parts. It is also handy for warming the surfaces before applying the paint and partly curing them between coats.

Enamels tend to be thicker than the usual aerosol type touch-up paints, it's important to apply thin coats and not get too carried-away trying to cover the surface too quickly.

Preparation is the same for any paint, the better it is the better the finish. I have never used a primer with Hammerite. All I do is use enamel thinners to clean all the surfaces before painting.

 

[gwigglesworth]

Stove enamel does not need to be baked on but you do have to choose the correct one.

On the hammerite due to the silicone in it it makes a slightly thicker layer, this can make detailed items disappear - more an issue if you have something like blacksmithed items as you can loose some of the tones. Its strange but it can be annoying, on a bike it is probably OK....

The best bet though is to get some good paint from a paint supplier - who might also be able to give you some of the excellent trade paints

 

[Packer]

Great info there thankyou.

The evil looking black gunge under the engine paint obviously need to go. If I use acid etch primer do I still need to get down to pristine shiny metal before application or will removal of all wet and loose material down to sound but discoloured metal be OK?

 

[MikeP]

Just key the surface. Don't bother with wed & dry, emery cloth/paper will do (it's not as if you are after the type of finish that you'd want on the tank).

Feather the edges of any areas where the coating has lifted, taking it back to clean metal.

I use a clean paint-brush to dust off the results of the keying and then thoroughly clean with enamel thinners.

If you intend doing the powder-coated items like the wishbone, it's best to remove the powder-coat. It's such a thicker coating and is more elastic than paint and corrosion can travel a long way beneath the coating without being visible.

On items like the shaft housing, as the powder-coat is on aluminium, removing it isn't as important because the corrosion doesn't travel in "worms" the way it does on steel. As long as you really key the surfaces well, you can paint over powder-coat.

I can understand why this may seem the best time of year to address these things but unless you have somewhere warm and dry you may not get the best results.

You can help things along by warming the prepared surfaces with a hot-air gun and standing the paint-can in warm water will help the paint flow (but don't use boiling water, a mate of mine has a scar on his forehead from an exploding can when he used boiling water).

Playing a gentle heat over the paint between (thin) coats helps it cure or when touch-dry stand them on a radiator. The black satin is the most difficult to get a good finish, the silver is almost impossible to bog-up.

 

[uncle dick]

FWIW I painted the heads on my 1100GS with aerosol smooth Hammerite and it's been fine. If you look closely it has yellowed slightly around the exhaust ports but that's being very picky. As to the thickness, it seems very close to the original.

In conclusion, I'll be happy to use it on the front cover when I find the time/inclination.

HTH
Dick

 

[roddy]

iv used normal spray on smoothright on jap engine casings, its never come off,,and i recon a 4cyl runs hotter than my old bm,
wouldnt use it on cylinders though

I would have though a an air cooled engine would run a higher surface temp since it does have the water jacket of a in-line 4 ?

sorry for the digression

 

[dmc]

used smoothrite all over engine two years ago still good as new no lifting or flaking

 

[MattW]

I've used smooth silver Hammerite on my front cover and rocker covers with decent (within the limits of the time I wanted to put into the job and my lack of skill!), durable results.

<a href="http://picasaweb.google.com/lh/photo/hbrgsqboHln1wP5PgfCaOBJAieIP4IByCYmMpeOVcwI?feat=embedwebsite"><img src="http://lh6.ggpht.com/_SSn2CtCOKnU/TG_4IdIdJJI/AAAAAAAADps/OyojCM2BOI8/s800/IMG_5641.JPG" height="600" width="800" /></a>

<a href="http://picasaweb.google.com/lh/photo/kJWskktLeeXMronrCLy8psdIjVbFe8lpPsa0N09Tvn4?feat=embedwebsite"><img src="http://lh6.ggpht.com/_SSn2CtCOKnU/TFHsjxKJfWI/AAAAAAAADgY/wFWI37t3OzU/s800/IMG_5584.JPG" height="800" width="600" /></a>

As Mike says, preparation is the key - I used a home made dremel tool to remove the existing flaked coating and feather the edges of sound paint. Plenty of thin coats onto pre-warmed metal, cured between coats using a hot air gun on low heat

<a href="http://picasaweb.google.com/lh/photo/ATpB4VsUwzLIdLBwoblURhJAieIP4IByCYmMpeOVcwI?feat=embedwebsite"><img src="http://lh4.ggpht.com/_SSn2CtCOKnU/TG_4jA_I3YI/AAAAAAAADqA/xZHBNWoFhcQ/s800/IMG_5635.JPG" height="600" width="800" /></a>

 

[Packer]

<a href="http://picasaweb.google.com/lh/photo/ATpB4VsUwzLIdLBwoblURhJAieIP4IByCYmMpeOVcwI?feat=embedwebsite"><img src="http://lh4.ggpht.com/_SSn2CtCOKnU/TG_4jA_I3YI/AAAAAAAADqA/xZHBNWoFhcQ/s800/IMG_5635.JPG" height="600" width="800" /></a>

I've got a garage I can work in and although it has an uninsulated Ali door I can ge a bit of heat into it with an electric fan heater or two.

Hammerite Smooth it is then for entire engine casing, rocker covers, gearbox, swing arm and final drive.

Satin black = difficult
Silver = idiot proof(ish)

That will be Silver then

to MattW for that brilliant looking home made Dremel tool. It looks perfect for around the fins etc. on the sump and rocker covers.

 

[mpgscott]

Has anyone used the hammerite smoot on the gunmetal engine cases?