Recently opened up the top end of my CB550F (a hasty move, in hindsight) in hopes of repairing a weeping head gasket and found that the gasket material had become pretty well stuck in a few places.
Although its been covered many times, I couldn't find a consensus among the threads as to the best method, nor any well-documented techniques and results. Aside from taking the head to a machine shop for resurfacing, the prescribed methods involve either scraping (usually with the aid of some gasket solvent) or abrasives such as Scotch-Brite pads/bristle discs or even sandpaper. I elected the scraping/chemicals route having heard enough bad things about abrasives on aluminum heads. For caution's sake, I started with some composite (plastic) scrapers.
Almost everyone who favors the scraping method prescribes some kind of chemical solvent to soften the gasket material. I went with CRC Gasket Remover, which sprays on like foam.
With a little elbow grease, scraping worked rather well for the bulk of the gasket material. After soaking both surfaces for about a half hour in the gasket remover, I would work in a rotation between the two decks; scraping at one while the other soaked. The tips of the plastic scrapers dull quickly but changing the scraping angle or flipping the scraper approximates a fresh edge. The whole process took about two hours.
<![CDATA[<a href="https://s3-us-west-2.amazonaws.com/cb550ptrfrncsmrph/HGR/IMG_2708_1.flv" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">https://s3-us-west-2.amazonaws.com/cb550ptrfrncsmrph/HGR/IMG_2708_1.flv</a>]]>What I was left with was the residue of some red gasket sealant in areas, on which the gasket remover and plastic scrapers had no effect.
I also tried spraying with carb cleaner, and then soaking with lacquer thinner overnight, before I realized I would need to switch to a harder scraper. I started using a flat blade scraping tool and then switching to loose replacement blades from a utility knife because the latter were less flimsy and also because I happened to have a lot of them lying around from a broken dispenser. I would hold the blade by hand scraping towards me at somewhere around a 45 degree angle. The precise angle for getting underneath the sealant without nicking into the aluminum is tricky to find at first, so if anyone else has to go this route I would recommend rehearsing on the least critical areas of the head where you're not likely to gouge a passage between cylinders or from a cylinder to the outside, and having sufficient lighting to be confident you're not pulling up any metal as you scrape. I had a few close calls, hopefully nothing that would compromise the seal between the heads, but I'd appreciate an outsider's perspective:
And this is where I'm at now:
I've scraped at an area of this residue for over 15 minutes, and although a little seems to collect at the razor's edge, I don't seem to be having any noticeable effect. I'm all for doing things the hard way if it's the right way, but is there a way to get this residue off short of scrubbing at it with some sort of abrasive?
