Sam Jacoby

CB500 Top-end Rebuild

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The CB500 has long had a weeping head, the evocative term for the scrim of oil that filters down from the head-gasket. After a long ride, a film of dusty oil coats the fins. It’s been that way since I bought it. It’s a common enough problem on these bikes, and the typical solution is to ignore it until it gets so bad that your pants are soaked after a lng ride. That’s not exactly my style—and more to the point, the #1 cylinder was continuously fouling, coated with an oily black concoction that stifled the spark. That’s a sign of an oil leak somewhere in the mix.

So — winter-project — for beauty and glory, rebuild the top-end—new gaskets and rings. I bought the Versah-155 gasket kit and a new (old) Craftsman V-Series ratchet, and got cracking.

Theoretically, replacing the head gaskets is a standard-enough job. On the 500s, can even be done without pulling the motor. Needless to say, the easy way isn’t always the most appealing, and I wanted to paint the cases while I was at it.

Out the motor came—a one-man job, believe it or not. The entire hunk of aluminum weighs something less than 150lbs, making it just within the range of the possible in a few solo heaves. The fine gentleman of the forums described putting a 2x12 under the motor (after removing the oil pan) and jacking it up and out with a bottle jack. Worked like a charm.

Trials & Tribulations

On removing the jugs (this is, believe it or not, what the section of the motor that contains the cylinders is called), the steel cylinder studs, that bind the entire mechanism together) were exposed. In a fit of completionist fervor, I decided to pull them. This was a mistake. The crankcases are alumninum; the studs are steel. Where the two meet, a delightful chemical reaction takes place: galling. Effectively, this means that the studs very much did not want to be removed. So commenced a month-long battle; an interminable series of hammering, tapping, freezing, heating, dipping, torquing, and so forth. I’d walk out into the bitterly cold garage, heat up the studs as much as I could, drop in some Kroil (some sort’ve fancy oil), give it a couple whacks, and go back inside. Repeat. It was idiotic, bu oh-so-satisfying, when at long last, the stud would spin out.

Needless to say, in true amateur fashion, I botched one, snapping the stud off flush with the gasket surface. I had to haul the case into a local machine shop, who managed to extract it for some insane sum. Such is how progress is made. Such is life.

In which diligence goes unrewarded

After arduously peeling off the age-old gaskets, I brought the cylinders into a machine shop, and had the surface decked and cylinders honed. Pro-tip: if you’re going to bring anything, don’t bother cleaning it yourself. Decking obviously cleans up the surface better than anything you can do; and most shops have an insanely toxic heated bath or some kind, that’ll strip any caked on gunk and oil off. These are the things one learns, though I don’t regret the 200 hours I spent with a razor blades and beer.

Lapping the laps

I also lapped the valves, a pleasantly-antiquated procedure, in which a bit of gritty compound is rotated between the hardened-steel valve lip and its mounting face. As satisfying as it was, I never quite got it right. You shouldn’t be able to see any light between the matings faces; and it should hold gasoline when the valve springs are back in place. I mean, the head had 35 thousand miles on it, with who-knows-what history, so it was always possible they needed to be recut. It was disappointing that my magic-marker and elbow-grease techniques were not enough to make a gas-proof seal. But what is life, if not but a series of small disappointments and humiliations?

I probably should’ve shipped it off to the vaunted head specialists, but I took it to my local guy, who seems to know what he’s doing. The folks on the forums would blanche that he didn’t have a Serdi machine. That is, for the uninitiated, a very special machine used to grind precise matching angles on the valve seats.

A Coat of Many Colors

With everything taken apart, I wanted to paint the cases. It was a surprise to me that motors are generally painted. They look like bare metal, but in fact, are painted a metal-color. I masked off the openings, which is a very satisfying activtiy.

So, a few cans of high-temperature rattle-can VHT later (and a questionable stint in the oven to bake the paint on, and I had a pretty credible looking motor.

Cases prepped for painting.

Back together, now

With the head back together, the cylinders honed, the pistons scoured, etc., etc.,


Versah-155 Gasket Kit, Stainless steel engine bolt gasket kit APE HD Studs Aftermarket CB500 ringset,145643.msg1660939.html#msg1660939