Valve cover corrosion on D17s
 

As you may've read elsewhere, I've recently swapped my VC gasket, which was so easy it was almost like working on a motorcycle engine... aside from actually getting to one that's wrapped in an aluminum twin-spar frame. :hgrin:

There was the usual hardness, and the tech who'd swapped the last gasket had gone super-nuts with the super glue (which is a thing -- helps retain the gasket in its groove, preventing foldovers and dropouts without compromising sealing... as long as you don't glue the ENTIRE gasket in. Tack here & there and Bob's your uncle.). I sure hope the factory doesn't deliver gaskets like that...

However, one spot where the gasket was particularly hard and beginning to get rocky, was right above the exhaust, in a 1/2" length. It was also loose there, hence the greasiness on the front of my motor. Pulling away the gasket, I found something weird...

Under that spot, was a little mound of black, crumbly powder -- scraping it away with a flat-blade, I found a little crater of aluminum surrounding it. I was able to push down the sides of this little crater (all within the groove), so it'd seal. The cover was filthy, so shot it down with 3M brake cleaner (miraculous stuff) to de-grunge-ify it, and found more crumbly-black-filled blisters, like rust on a car body. Tapping them, it felt between charcoal and plastic dust in consistency. I'd also noticed when swapping out the seals, that the cover'd been painted.

So do OEM covers corrode like this? On the moto side, an aluminum cover is an aluminum cover, and my old Paseo cover was also cast aluminum. Not sure if Honda followed Ford's lead in sintering parts to make more complex shapes... but wow. This cover is definitely strong enough to do the job though (I'd tapped in new plug tube seals no problem)... except for the spots where it wasn't. First time I'd ever seen anything like it. Maybe a Chinese knockoff part installed by a shady shop? The previous owners weren't at all conscientious about OEM anything, so it's a possibility.

Anyone else seen something like that? I sure hope it's not an OEM part... that would be disappointing. :confused:

Re: Valve cover corrosion on D17s
 

It's aluminum. Once corrosion gets under the layer of paint, it's hard to stop it.
Maybe it had already started corroding when the last person put the gasket in, that's why it got yuckumpuckeyed?
Previous hardened gasket wasn't completely removed? I know they can set in like concrete sometimes.

I don't like to glue the gaskets into the groove, but then maybe aftermarket gaskets don't fit as nice as OE. I just dab the gray into the corners on the cam humps.

Maybe aftermarket uses a different rubber compound too, that's why it hardened? I know heat makes the rubber harden over the exhaust side, that's natural.
The OE gasket seems to stay pliable for a long freekin time.



Make sure you got the round tube seals fit all the way around the tubes, sometimes an edge of a lip wants to hang over the end of the tube and fill it with oil.

Re: Valve cover corrosion on D17s
 

Yep -- all of my gasket swap parts (gasket, tube seals, bolt hole seals) were from Majestic and OEM parts. When it comes to seals, I don't trust anything but Honda on Hondas...

I don't like that grey Hondabond, though. I find as it ages it gets harder and harder, until it resembles resin, then begins to leak (Yamabond, Yamaha's formulation, is far superior -- but as Yamaha and Toyota are joined at the hip, I'm sure your overlords would take exception to seeing it in your box. Or not. ;) ).

Mind you this is with huge temp differentials on 600 and Open-class sportbikes and ATVs... but I much prefer Permatex Ultra Black, and it's been quite successful at doing its job over the long haul in many applications (three of which were my own vehicles). The stock cover has little kinks in the groove specially made to retain the gasket anyway... I ended up using a dab of UB in the sharp corners to retain further, which may or may not have been necessary... but it is nice to know it's redundant protection (and we know my stance on that, when it takes mere seconds to do). ;)

Yeah I did notice the tube seal on one tube had ridden up over the lip of the tube after seating the gasket... but easily tucked in with a gentle roll with a blade screwdriver, painless.

I'd never seen a cast and machined valve cover develop corrosion like this... but then again, most of the ones I've seen are bare aluminum, painted, from the factory. I wonder if the old-school wrinkle-finish ones from the '80s developed this corrosion business -- first time I'd ever seen it. Apparently a previous tech or owner shot the cover with another layer of paint... which I guess means I'm looking at another valve cover down the road.

Re: Valve cover corrosion on D17s
 

My cover is holding up very well.

Could yours be caused by the salt air from the ocean? Island life is catching up to it.

Re: Valve cover corrosion on D17s
 

^Could be. But where I lived near Seattle (Bainbridge Island) was just as salty (if not more) than here, and I'd *never* seen fully-exposed aluminum valve covers on motorcycles corrode like that, even commuting through full winters. Then again, I've not come across a whole lot of painted aluminum covers either. The salt spray moisture here doesn't tend to affect aluminum as badly as of course steel IMHE, but I have no idea what happens when it's caught where it can't escape.

At first I thought maybe acid was dropped on it, then cleaned off sloppily before the second coat of paint went on, as it's happening only in three or four spots on the cover. Al2O3 is usually white, but in alloys it can appear graphite grey when oxidizing. This stuff was dull matte black, though.

Ah well -- mystery for the ages. No (visible) effect on function other than that blister in the gasket groove, so no biggie for now.