® Early Honda V4 Cams: What Really Happened

The first-generation Honda V4s were and still are magnificent testimonies of Honda's engineering prowess. From a sociological standpoint, the bikes attracted some interesting people fervent about their riding. This group has contributed significantly and meaningfully to the web community, and it is blessed because of this. One aspect of these bikes that is thoroughly represented is the issue of camshaft failures in the earliest models. Unfortunately, like so much that is "common wisdom", most of what is said about the subject of first-generation Honda V4 cam failures is wrong. Dead wrong.

The Internet is at the same time a blessing and a curse. A blessing because it quickly codifies major thought streams on a subject. But a curse also because often the user forum organism breeds a decay that necessarily colors and constrains the collective information. The result is a one-dimensional thinking that regards problems in very superficial ways that are often ill-informed. The fact is, despite much that can be read on the net, the controversial first-generation Honda V4 cam failures are not explained by anything as simplistic or as singular as lubrication. In fact lubrication doesn't enter into the picture at all.

The truth is, similar to what goes into making a cake, there are actually four critical ingredients in the extreme camshaft wear issue. Not one, not two. But, four ingredients came together in an unhappy combination that results in a sum greater than the parts, so to speak, to create our huge cake, er, cam, problem. :-)

Ingredient 1: Historical Asian cam and follower construction. Aftermarket cams are made in a number of ways, but production Japanese camshafts are pretty consistently metal castings. Cheap, in other words. This means most production Japanese cams until about 2005 are actually cast iron. Yup, cast iron. Better ones are cast steel and the very best production cams are cast moly (in the Kawasaki ZX-10R and other sportbikes, for example). But far and away, street bikes have cast camshafts.

It may surprise you to learn that production camshafts are not hardened very hard. Don't believe it? You can actually drill a camshaft from a 70s or 80s Japanese street bike, and you don't even need a fancy cobalt drill bit to do it! A sharp HSS (high speed steel, the standard drill bit material) will drill a cam lobe easy as, uh, pie. This is probably why the cams in most 70s-80s Japanese multis wear pretty steadily, about 0.001" for every 3,000 miles. Most mechanics are aware of this. And experienced machinists will recognize those distinctive cast-iron chips.

The cam's followers (rocker arms) on the other hand are extremely hard. It is common machine engineering practice to have two close-working parts be one soft and the other hard. Thus the cams are somewhat soft, and the followers extremely hard. The cam does most of the wearing in other words. The follower wears only if the camshaft wears severely, or the engine is run low on oil. Otherwise, not.

However the follower is not hard because of superior material, but because it is plated. Many of Honda's rocker arm type engines have their rocker arms or followers hard chrome plated, chromium being an extremely hard material, thus long-wearing. But don't confuse hard chrome with decorative chrome. Same metal, different process. When a part such as a handlebar is decorative chrome plated, it is plated first with a softer metal such as copper (and often tin below that), then the chrome is put on top of the copper. The copper plating gives the chrome depth, and adds gloss as it fills in tiny imperfections in the base material.

Hard chroming on the other hand is simply putting chrome on top of the base metal, with no undercoat, which is why it is much rougher looking and was early on called "flash chroming". Your bike's transmission shift forks are done this way, as well as the fork tubes. And, the cam followers.

So the first ingredient in the great V4 cam debacle is the soft/hard cam/rocker interface. Ingredient 2: How the mass-produced camshaft is ground. Cast camshafts are ground to produce the planned profile and desired surface finish. Japanese engine manufacturers cast the cams extremely close to final dimension, then very lightly grind them to size, because a manufacturer producing 15,000 vehicles doesn't want to waste much. And, even more importantly, he doesn't want to grind through the surface hardening (cams are not hardened as the last step but as an intermediate step, so warpage can be corrected after by grinding.) In other words, the grinding aspect of cam manufacturing just barely cleans them up.

Unfortunately, cams made this way tend to have defects in the metal just below the surface, because most of the metal's impurities migrate toward the surface in a casting, even with modern technology. The very slight grinding doesn't go very far below the surface and therefore doesn't get past and remove these defects. Engineers call these pockets of impurities "inclusions". It's an inevitable part of castings. This cam is from a Kawasaki GPz900, another machine with the same cam problems as the Honda V4. And for the same reasons.

So, ingredient number one is the soft cam/rocker intface, and number two is the presence of air pockets in the cam casting. Ingredient 3: The emergence of high valve lift. Honda for decades was very conservative with valve timing and lift specs. Honda's 1970s era bikes have only 5mm (less than a quarter inch) of valve lift, and timing numbers in the 5-40 range (giving just 225 degrees open duration). Very mild cams. Until the mid 1980s.

You can't appreciate how extremely moderate this was until you look at Kawasaki and Suzuki specs from the same era, typically 7mm lift and 15-55 timings. In fact, you can rev an old Honda SOHC four to the moon, way past the engine's redline in other words, and the valves will not float (that is, overpower their springs and flail around and tangle). They're just not working hard enough to. (I am not recommending this practice, for the record.) Modern higher lift cams require stronger springs to avoid valve float. Later, Honda started creeping toward higher lifts and the first major production U.S. model street Hondas to reach into the 10mm mark were, you guessed it, the 1982 Magna and Sabre.

Okay, number one is the cam/rocker interface, number two the cam's air pockets, and number three unprecedently high spring pressure on the cams through increased valve lift. Ingredient 4: Tandem cam followers. Coinciding with this high performance cam spec was Honda's move to dual followers, that is, one cam lobe operating two valves in a four-valve cylinder head. Honda had used dual followers before, in fact, in its debut four-valve head on the 1972 XL250. But remember, the XL250 engine, like those that would follow for several years, lifted its valves only 5mm and didn't rev all that much either. What dual followers did, back then but more importantly later in the V4, was greatly increase the specific loading of the cam lobe. bNow instead of two valve springs, four springs bore against the cam lobe. And in the case of the early V4, these springs were unprecedentedly strong ones (because of the high lift, remember).

Okay, so number one is the cam/rocker interface, number two the air pockets, number three the uigh spring pressure, and number four the multiplicity of springs bearing on one cam lobe. Now let's mix this stuff together. Let's see how these four things worked together to create the problem of cams that seem to crumble like aged cheese.

In normal use the cam wears, and the hard chrome plating on the followers scuffs just perceptibly, as the engine accumulates miles. Normal. This example is typical. Nothing to be concerned about. I have seen engines with 50,000 miles whose followers looked like this one.

If the cams' pits are small and/or very stable (not increasing in size or number), the cam is not in trouble, and will likely live a long and happy life. Like this example.

But if the pits keep popping out like acne, or cover a significant portion of the cam lobe, the lobe becomes abrasive to the point that...

...it begins to affect the hard chromed follower (rocker). The follower's chrome overheats and abrades, actually buckles. This rough treatment of the follower by the camshaft has severe results. The follower's plating splits and then begins to come off the follower in strips. The follower is now a cheese grater. This is the point where things start happening, the point of no return. And it happens fast from this point onward.

With the follower's surface now a rasp-like texture forced against the soft cam lobe, the cam quickly tears up. If unchecked, the lobe can even be worn completely away! This example is almost to that point. Unbelievable! And extreme. Few cams get to this point.

So the chain of events is: Pits develop on the cams and if bad enough they excessively abrade the followers. The followers then in turn strip off pieces of their chrome. The resultingly raspy followers then chew up the cams. And it all begins with the pits.

The problem isn't poor oiling. I have nothing against the many oiling line kits out there. But the idea for these kits came from a different problem altogether, one experienced by racers (including myself) having to do with cracked overhead oil lines. Team Honda and others did not install special oil lines in their Interceptor racebikes for inadequate oiling reasons, but because the stock rigid oil lines didn't stand up to racing conditions. Nor was the problem petroleum based engine oil. It's not oil related at all. This is precisely why some first gen V4s had cam problems and some did not. It was all up to the happy coexistence of cam and follower, which in turn, again, goes all the way back to a minimum of cam inclusions appearing during the normal wear process.

And it wasn't improperly adjusted valve clearances, despite Honda's effort at blaming their dealers and diverting attention with their goofy cam tool. Typical corporate nonsense, that. Total subterfuge. Honda even eventually admitted as much.

Nor was it badly made camshafts. They were made no differently than Honda made cams for any of their other models. Though some attempts were made to have new cams solve the problem. For the 750 alone Honda issued several revisions to camshaft finish, a few of them shown in this picture. Note the darker colors indicating various surface finishes. They were countermeasures, but they were all bandaids. Hopeless.

The way to fix the problem is to go after the cause. What is it again? Yup, pits in the cams. If your cams have significant pits, they need to be reconditioned. If no pits or very tiny ones, then at least have your followers hard-welded. Megacycle offers this service, and it is the best solution to the problem. This eliminates the hard chrome that can strip off, and provides a hard, durable surface that is very much more difficult to hurt. This cam follower is a part going into a V65 I restored some years ago.

If there is any question as to the cams' condition, get them hardwelded also, just like the followers. Megacycle will offer you the choice of a stock or slightly modded profile, but pick the stock one. Focus on repair, not hot-rodding. My choice would be to do both cams and followers. This way they both get the hardened surface they should have had from the beginning, and you can expect them to last a very long time. This cam went into the aforementioned V65.

 

In an interesting, ironic and even serendipitous twist of reality, user forum members have responded to this article have by accusing me of being some kind of shill for the Megacycle company. Wow! Just goes to show how one-dimensional some folks' thinking can be. Incredible! I am not advocating Megacycle as a company or its products. I am showing what any thinking person should recognize is the problem and identifying the only real solution. Follower hard welding has become a pretty significant practice these days due to the chroming ethic Japanese manufacturers default to and its inadequacy. Take advantage of the fix that is available.



  Suggested further reading on this site:
More on V4 cams
First generation V4 fallacies
Julian Ryder's book
The introduction of Honda's V4
Early VF750 cam supercessions
V4s in the dealership
Honda first-generation V4 bulletins

Email me
© 1996-2017 Mike Nixon