The Latest from Terrible
where I document the existential struggle of rebuilding and maintaining a vintage motorcycle or two- what I've learned, mistakes I've made, what lessons I may glean for my day-to-day, and counter the persistence of time's corrosive and terrifying hand. Also some recipes and stuff. Enjoy.
Project: 1971 cl100
Project: 1980 cx500
Project: 1979 CB750F
Last year, I purchased my friend's 1979 cb750F Super Sport. I wasn't familiar with the late 70's, early 80's DOHC engines, but I had rebuilt a Golem of a '73 500K from dirt and stupidity and dreams; so I was pretty familiar with the air-cooled, across-the-frame 4-cylinder layout Honda was working with. I only saw a picture of the bike he called "Boomer" when he was riding it and it was all polished persuasion. Not the sad and ugly bike I traveled 2 hours in a U-haul to pick up. Two years since running, in and out of weather, raking heavily on it's kickstand; a bad rectifier was what grounded it, but it had clearly been through 50,000 miles of shit.
It had been wrecked, and more that once. There was a gaping hole in the stator housing from a car striking its right side. The aluminum had broken in several places like a bad taco. Duct tape covered the holes. This was the second time my friend had been struck on this bike. The first time, a truck ran a red light. He attempted to accelerate out of its path but the truck hit the left rear of the bike, spinning it around. He found himself facing 90 degrees from his intended, and still riding, only now toward sidewalk pedestrians and a downtown Milwaukee shopfront. He regained control and avoided a grim end.
As run-down as the bike was I was willing to take on another project. After all, I'd already rented the Uhaul. I paid $500 for the bike which, in its condition, was on the high side. But my long-suffering friend had put a lot of money into it over the years and had all the service paperwork and a clean title. Besides, he had paid the same price when he took its ownership ten years earlier and he seemed pleased with the symmetry of the transaction. Wouldn't want to jinx all that good luck he had with it by upsetting the universal symmetry, I guess.
Honda introduced their first OHC, air-cooled, in-line 4-cylinder bike in 1969 with the cb750K. It had a single overhead camshaft that drove a total of 8 valves. There is cool anecdote about Honda's program here:
Okay, so we all know this. But in the 10 years since that seminal moment, they developed a number of sizes of the same basic bike, including the cb500, which I talk about below; and came immediately on the heals of the 750; in production, if not on the track. In 1979, they revealed a new take on that engine that was born out of a market for faster, higher-revving large cc bikes (the 750 was considered pretty large in those days). With the new design came a double overhead cam configuration and a whopping 16 valves, 4 per cylinder. It red-lined at around 10k rpm and above 6-7k, came to life like a bee-stung feline. The race-tuned versions of the later 900cc and 1100cc sizes killed it on the track, especially in the endurance competitions. They were tough, simple, and versatile. Here is an account of the 1980 750 version being tested against the Ducati 900 Desmo- with particular attention to the Honda's surprising handling abilities.
Unfortunately, around the same time, emission standards for motorcycles became more strict in the United States and the stock bike they offered consumers was tuned and jetted to a tamer attitude. To glean the full potential of this bike, you have to do some modifications.
Fist I replaced the rectifier. Then the battery. Then the oil. The carbs had to be cleaned and the old gas evicted from the tank. I wanted to get it running right away so I could give it a listen and get a sense of what all the problems may have been. Pulling the four carburetors from these bikes is like pulling teeth from a crocodile; something to avoid if possible. I put in new gas, along with a can of Chemtool to begin dissolving any lacquer the old gas may have left.
The carb boots were in bad shape, cracked and hard. A problem compounded by there expense and rarity. The more cylinder there are, the more expenses you'll incur. Naturally, servicing the carbs on a two-cylinder bike will cost half of that of a four-cylinder. A consideration oft over-looked when dreaming of all the extra horsies. And if the bike is 30+ years old, you can expect to be replacing most, if not all of the rubber bits. Even with the quality of Honda's rubber, over time it will out-gas the elastomers that make it pliable and become as stiff as Lincoln's corpse.
When the stubborn old horse finally coughed and churned back into being, its slumber shaken off; the valves shot fire from the Kerker exhaust and I smiled the smile of a proud father.
Project '73 cb500K2
About year ago, I bought a 1973 cb500k from a guy on craigslist for $50. I'd been looking around for a vintage four cylinder sport bike since sucking the fumes from my friend's '74 550k, while I rode behind on my 78 cb400A twin. They aren't even in the same class so, as I fell behind, I vowed to be the Petty Man and get my own. I went to see the bike, and though it was dark out, and the bike was in pieces (the toothless man who greeted me was named "Tinker"), I knew it was pretty complete and had the original paint and side covers. In short, I knew I wouldn't lose money. The emblems alone were worth what I paid. After getting it home; through deep snow, in a borrowed 4x4; I looked it over and cursed myself for making another man's trash my own trash- and paying him for the privilege.
My first idea was to just clean the thing up and ride it as soon as I could. That was a foolish thought. I started by cleaning all the parts with Mean Grean™, PB Blaster™, and a lot of Scotch Bright™ and steal wool. I found a number of problems that weren't as apparent under the dim housing project streetlights where I first encountered it. The upper triple tree was broken and the lower one was bent where the fork tube ran through it (the upper is cast aluminum; the lower, steel). The rear wheel was in a lot worse shape than the front, completely rusted with the sprocket and chain basically trash. The hub itself had mismatched bolts holding the sprocket, and over time these smaller bolts had worn the holes out as the sprocket was wrenched back and forth. I briefly toyed with the idea of repairing the hub with helicoils for the bolt holes and re-lacing a newer rim with newer spokes. But such is the folly of the stubborn and enthusiastic amateur, to waste his own fucking time to gain knowledge of his own fucking ignorance. I later abandonded that notion and found a nicely preserved and complete front end and rear wheel for $300.
The big challenge was the seized motor. After mostly reassembling the bike I tried to move it and discovered the engine was stuck but good. After some excellent advise on the SOHC4 forum, I took the spark plugs out and poured a batch of 50/50 ATF and acetone down into the cylinders. After about 2 weeks of soaking, I was able to free up the engine. A twist with a breaker bar on the stator bolt and the 50/50 mixture of liquid death shot 10 feet in the air. I was lucky to have had my head turned or I would surely have been blinded. Goggles, people; use them. It turned freely after that. The motor had a visible previous head gasket leak and was caked in oil, dirt, grease, and a variety of effluvium. I knew I'd have to take off the top end and see what I could see.
I pulled the motor, for which getting the protruding oil filter housing off was the biggest pain in the ass. I ended up having to grind off the head of the bolt which I later replaced. After doing some research, I'd thought of getting a vapor blast kit and using it on the motor. The vapor slurry gives aluminum a luscious matte silver finish. But, after I used about a gallon of degreaser on her, I thought the high heat finish Honda used looked to be in pretty good shape. I figure she only looked new once.
More to come...
70's era Japanese motorcycles, including twins, singles and 4 cylinder 4 stroke engines. Photos by Terrible Rider.