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pouakai
19th November 2012, 21:35
I am renovating a ducati 900 (circa 1990) engine that was exposed to coastal air for much of it's life.
A fair percentage of the factory powder coating is flaking off and lots more is compromised, I wish to completely strip it back and repaint.

What is the best method for striping engine paint ? The engine will be fully built and out of frame at the time. I have heard of some using soda blasting to this end but of course I would be very hesitant to go for abrasives near an engine.

And for the repaint what is recommended ? Powder coat ? baked enamel ?

Cheers,
P

Akzle
20th November 2012, 06:14
i think most people will tell you to soda blast (plug all holes you don't want blasted) and 2k paint afterwards.

jim.cox
20th November 2012, 07:19
Be VERY VERY careful if do use paint stripper - most are strong Alkali and will fuck (thats a technical term) aluminium surfaces faster than you can blink

DEATH_INC.
20th November 2012, 14:25
Be VERY VERY careful if do use paint stripper - most are strong Alkali and will fuck (thats a technical term) aluminium surfaces faster than you can blink
No, paint stripper is fine on ally, we strip wheels with it all the time , and I've stripped bike cases with no problems. If you aren't going to strip the engine tho it will fuck (that technical term again) the gaskets and seals.
Soda is recommended as it desolves in liquids (oil water etc) so if there's any lurking in the corners it should disappear before it does any harm. In theory anyway...

jim.cox
20th November 2012, 15:27
No, paint stripper is fine on ally, we strip wheels with it all the time , and I've stripped bike cases with no problems. If you aren't going to strip the engine tho it will fuck (that technical term again) the gaskets and seals.
Soda is recommended as it desolves in liquids (oil water etc) so if there's any lurking in the corners it should disappear before it does any harm. In theory anyway...

Well I dont what was in that stripper that Pete used, but it sure as hell fucked his engine cases. You sure you dont use something special?

Agree that soda blasting is the best way to go

Laava
20th November 2012, 16:03
I actually sand blasted mine but i was extremely careful to plug all inlet and exhaust with ali plates and silicon and then tape. After painting I removed all side covers incl clutch and cam covers for a different coating and maintenance, and there was no ingress and even the gaskets were almost untouched. (I was replacing them of course) Can be done if you are careful but you would absolutely be best with soda if poss. Good thing about blasting is it is immediately ready for paint. i used a high grade spray can job and it comes up mint if you are patient.
Have had no probs with paint stripper either, it is the shit for getting rid of the varnish inside cases also if you have it apart.

DEATH_INC.
21st November 2012, 08:31
Well I dont what was in that stripper that Pete used, but it sure as hell fucked his engine cases. You sure you dont use something special?

Agree that soda blasting is the best way to go
You sure he didn't have magnesium cases/covers? It eats that stuff no worries (ask the young fella who put a Ferrari wheel in it when I was away doh!). We use both immersion and paint on, but the only thing special about our stuff is we get an extra strong mix made up.

imdying
21st November 2012, 08:36
Vapour blasting is all the rage these days... I know there's a guy in Puke doing it FWIW.

Grumph
21st November 2012, 14:14
Vapour blasting is all the rage these days... I know there's a guy in Puke doing it FWIW.

No one in the SI to my knowledge yet though...

It's a better finish if the bits are not being painted - using water as the abrasive's carrying medium it leaves a closed pore surface versus the open pore of normal bead. Open pore gives a better paint key.

supremacy
23rd November 2012, 07:45
Thinking about doing this to the casings of my Duke. When the previous owner had it the battery overflowed and there are now nasty acid burns down one side.
Was going to leave the casings on and sand them down, mask everything with a sheet and load of tape, then rattle spray with high temp duplicolour matt black. Anyone done it this way? Not keen to remove the engine, and rather not remove casings if I can get away with it ;)

F5 Dave
23rd November 2012, 16:20
This rages through the resto bike mags from time to time like CMM & Practical Sportsbikes. There have been some places that claim they can blast stuff by very carefully masking.

Although the most recent batch was someone taking the place to court as their engine failed as a result. Doesn't take much to get in there & one of his witnesses said that he'd had to repair a few bikes done like this & was not recommended practise. He won his case.

The last paragraph speaks volumes.


I think the answer is either
a) live with it.
b) do a rattle can patch up & live with the tepid results.
c) bite the bullet & take it apart, accept you will have to buy the gaskets & do it properly.

you'd only do c) if you liked the bike & wanted to keep it. Maybe its time for rings & a valve tickle up.