Advice -- painting cases -- inside where the crank runs

[Gippslander]

Have just had a set of Husky CR450 1972 cases cleaned -- came up nice -- but the faces where the crank webs are have got hundreds of little pinholes -- they don't look deep -- more like some sort of corrosive pitting.

Should I paint to seal 'em up or leave them as they are?

And if painting -- what's the correct paint to survive in there?

Thanks

[flattracker]

as no one has replied I will put my 2cents worth in. Engine builders use electrical motor paint inside the engine under valley covers etc, to help the oil run off the casr iron. This is much cheaper than polishing internal surfaces and a lot quicker!
Hope this helps.

[Gippslander]

Thanks Flattracker -- ok -- that's a good lead and I will follow that up because I want to get the Husky right -- or rather as good as it can be on the build -- want it to be a long lived solid performer.
Have been doing some stickynosing around here and have been speaking to a fellow who has a bit to do at the local airport where there is a worksop that reconditions aero engines and he says that there is a "special dip" that freshly cleaned ally aero engine parts go in that seals up the ally before it is painted -- he says it gives the ally a gold colour (I imagined CZ hubs but I don't think so -- have seen that at Jiri Starec's near the old CZ factory so it will be interesting if it's the same)
So I will try to get there to the workshop tomorrow at beeroclock  and he will show me -- will report back.
And made another enquiry -- with an ex RAAF aero fitter -- he told me how they painted alloy engine parts -- says they preheat in an oven then spray an etch primer then back in the oven then later in the oven again and then spray enamel paint then back in the oven. He also knew about the abovementioned dip to seal the ally but said it was an acid a bit similar to battery acid that had a copper anode in it for 48 hours beforehand and that it turned the ally a grey colour that there was then a careful drying time in a heated room before painting.
And the ex raffy also told me about repairs with epoxy, he said they must not be done straight onto the ally because they will soon loosen because of a reaction between the chemicals in epoxy and ally, he said that epoxy repairs must only be done between coats of paint.
All probably a bit anal when years ago I would have washed all in petrol and put everything back together raw and then rattlecanned the whole lump satin black 
So I'm still none the wiser about the little pinholes -- but I do know not to use epoxy to fill em'.
I will probably just try the "dip" the fellow will show me tomorrow and I may even try a hard hand polish first with stainless "steel wool" to see if they can be closed up a bit by working them.
Will see if I can get some photos.

[Davey Crocket]

The electrical paint they use I'm not sure if it is OK directly with petrol as its going where the crank is, Ive used it on V8 engines and it holds up OK. Some of the paints/coatings these days have very good adhesion so my 2 bobs worth would be paint then use a epoxy type sealer. Make sure everything is cleaned within an inch of its life and I would probably pull the barrel after running in to check for flaking. Good luck.

[Gippslander]

Some photos

Above is inside the case wherethe crank runs

Above is where the clutch rod is activated from -- you can see the same "pit holes" so cannot be from combustion, must be a casting fault/imperfection

Above is where the cylinder sits, so again cannot be a from combustion because this is protected by a gasket

[Stewy138]

Painting cases is one thing Ive had no luck with over the years, have tried a few differnet paints, including VHT, caliper paint, 'engine enamel' and others. Tried thin and thick coats of etch primer. Nothing lasts longer than a few rides without looking like shite. Takes only a bit of petrol exposure to lift the paint.

The original factory paint on the cases is a different story - wont come off with paint stripper, not easily anyway. And takes ages to get off with wet and dry. Big difference.

[mitch75]

Maybe POR-15. Send them a email to check if it would work.
http://www.por15.com/POR-20-ALUMINUM/productinfo/P2H/

[Gippslander]

Thanks Mitch -- have sent the POR people in Sydney an email  -- will see what they say

[mitch75]

How did you go with painting the inside of your cases?.

[Bitten]

This might be a dump question but can cases (aluminium & magnesium) be powder coated and if so is this more durable / fuel resistant?

[Gippslander]

Hello Mitch, have not as yet done anything, too busy in the lead up to Christmas but will get at it over the Christmas break,  I telephoned the POR People and they recommended a particular paint, so I ordered that and have it ready to go, and a fellow who works at the local aerodrome and does engine reconditioning says that he has a special dip that cleaned aluminium and/or magnesium parts need to be put in to treat/seal them, he doesn't know much about what the dip is but he says that it's just routine with aircraft parts and  they only have to go in for about a minute,  so I'm going to do that with all of the engine parts and a KTM magnesium rear hub that I have had soda blasted ready for rebuilding into bright and shiny wheels.
As to the painting on the inside of the cases, I just haven't made up my mind as yet, I'm thinking "what for" and will I be causing some problems later on if the painting comes away, especially because the little holes you can see the pictures are just minor porosity (admittedly a lot of them) and its obviously been there since the cases were brand-new so if they were not a problem for Husqvarna I'm not sure I should be worrying about it, anyway I'll certainly get the dip done at the aircraft place And get some photos of that process and post them up and I'm still thinking about the painting on the inside to seal up the porosity.
Anyway I finally worked something out – thinking and deciding what to do is the most time-consuming part of maintaining old motorcycles