Debunking 1st-Generation V4 Camshaft Myths
A Rebuttal to Internet Misinformation
Relating to 1st-Gen Honda V4 Cam Wear
A fellow instructor at MMI back in the 80s actually drove hundreds of miles each week from his teaching job to a Honda dealership out of town because the shop had no one who wasn't completely mystified by Honda's new V4. That's right. The dealer hired outside help. Seems that difficulty persists even today. There is so much wrong infomation out there regarding the engines in Honda's 1982-1985 VF500s, VF700/750s, VF1000s, and VF1100s that it is hard to know where to begin. A handful of websites in particular are particularly egregious in their posturing as fact a huge collection of myths. Take note that this rebuttal is in no way an attack on an individual or individuals. Here then are ten of the more common errors. By the way, my friend now heads up Yamaha's dealer training.
1. Some websites suggest that the use of tandem feeler gauges is some special technique that few know about. Hard to know where that comes from, when the bulletin on this technique was issued within the first few months of the V4's initial release. Websites and forums should promote the use of two gauges and explain why it is necessary, and just as importantly cover the proper technique, which is not at all intuitive. I call it "downhill" adjustment.
2. Many of the Internet "experts" encourage the over-tightening of the valve adjustment locknuts. They then compound the error by failing to mention the difference between pre- and post- 1985 rocker arms as it relates to locknut tightening torque, and the relationship between this and the factory valve adjustment wrench.
3. Many sites are solidly in the "cam tool" camp, which is unfortunate, because this badly misinforms. The cam tool was 100 percent politics (and that mostly in connection with the Euro market), and nothing else. Even while they mention the tighter clearances the cam tool bulletin recommends, most writers fail to a) recognize, as any beginning mechanic would, the clue that the tool results in tighter clearances, not more accurate ones, and b) mention the fact that Honda formally and publicly distanced themselves from the tool a very short while after its introduction, apparently coming to their corporate senses as it were. This is Honda-documented and is referred to in my history article on my website.
4. Some on the Internet indict the cam chain's tensioner as a contributor to camshaft failure. Wow. Hard to see the connection. Moreover, cam chain tensioner premature wear was limited to the first couple year models. Revised tensioners with the larger shafts were already available by 1984, and mechanics were also already removing the rubber noise damping sleeves by that time, a very good field fix, by the way. Many was the time I removed the sleeves even on new tensioners before installing them. (And I atill have a collection of maybe 20 or so release pins the new tensioners were shipped with.)
5. One writer declares that a camshaft-related extended warranty existed, and it did. But, his page leads the reader to believe it was for all models, and reads as if the warranty extension was unlimited. Neither is the case. The extended warranty was for 700 and 750 Interceptors only, and was for only a very short time, as is usual with warranty extensions.
6. Excessive engine heat is said by many to be part of the camshaft pitting problem, and this is not true. Engine heat had nothing to do with it. Much hotter running engines have been made by Honda without camshaft wear being pronounced in those engines.
7. Presumably in connection with this, manually overriding the fan switch is promoted on some websites. The problem with doing this should be obvious, completely aside from the fact that fan switch failures have no documented relationship to camshaft wear.
8. The whole oiling question seems most sensational of all in connection with 1st-gen V4s. Lurication rears its ugly head as a supposed major factor in 1st generation engine camshaft wear on most sites, and this is unfortunate. It just isn't so. The only connection between the lubrication system and potential cam pitting issues in this engine is the fact that the steel, brazed-together top end oiling pipes tended to crack in racing use of the bikes. Such was the case in early racing efforts (including my own), and this alone lead race teams all over to fit handmade oiling lines, not any presumed deficiency in the oiling circuit as a whole. One rather significant thing these folks also leave out, in this regard, and something I have never seen mentioned online, is that the earliest engines had some oil gallery plugs come loose (behind the alternator rotor) which of course dramatically lowered oil pressure. There's an oiling problem for you! Everyone who owns an 82-83 model should confirm the tightness of this plug, which for some reason Honda failed to epoxy over as is their usual custom. This same defect occured also in GL1200s. In connection with oiling, the use of the Interceptor's oil line banjo bolt is on some sites promoted on Sabres and Magnas, supposedly to enhance oiling, and then this sin is doubled by suggesting that this was a factory-endorsed "fix.". Not only was it not factory recommended, it wasn't a fix either. Far from it. The Interceptor's chain drive engines had different oil banjor bolts than the shaft-driven Sabres and Magnas for one very good reason, no third member (right angle) output transmission and therefore no need for added pressure at the output shaft area. Fitting the Interceptor's oil bolt, an idea that surfaced shortly after the Interceptor's introduction in 1983, only changes the oil pressure at the shaft-driven bikes' third member, and is likely to have no result on top end oiling. Fear-mongering regarding oil continues with declarations that the 1st generation engine's oiling circuit to the camshafts bypasses the oil filter. While this is true, among Japanese-made engines it is not exactly unique. Further, what argues against this is that the kind of failures evident in 1st generation engine camshafts aren't of a kind that can be blamed on impurities in the oil. While anyone who knows about oil would confirm that most modern engines' camshafts are the parts most at risk in the presence of any oil-related deficiencies, there is no reliable body of information that supports blaming oil for 1st gen cam failures, and plenty that shows the situation was much more complex than that, and not incidentally was actually predictable given the emergence of similar problems in other manufacturer's engines. See my What Really Happened article for more on this subject.
9. "Line boring" is a term unfortunately tossed around a lot, to the misinformation and confusion of many. These folks miss the fact that while the machining configuration for the camshaft bearings is indeed different between 1st and 2nd generation engines, they fail to notice something else in these engines that is far more important, and not incidentally, of direct association with the camshaft pitting problem. Again, I will refer you to my What Really Happened article for the details.
10. Finally, for the sake of "cooler running," premium fuel is promoted by some on the Internet. Anyone who has worked around Hondas, or for that matter any of the Big Four brands, for any length of time, knows that their standard road models have always been designed to run on unleaded 87 octane for so long that this fact should be included in the Smithsonian! A Honda bulletin about this exists dated 1971, so we have to look at least that far back. Premium fuel is a bad idea on bikes not specifically designed for it (such as Honda's own Turbo and any number of current hyperbikes, not to mention four-stroke motocrossers). Premium carbons up the valves prematurely and is the cause of some of the top end work that needs to be done on Gold Wings, especially, as well as other Hondas.
There is actually a some good stuff on the net regarding Honda's V4s, and I enjoy reading about their history and current popularity. There are great tips regarding suspension rebuilding, carburetor restoration, and of course painting and overall vehicle restoration. It is a shame that in this one area of 1st-generation engines so much is misunderstood.
More early V4 assets on this site:
The introduction of Honda's V4
V4 cams: what really happened
A review of Julian Ryder's book
Early VF750 cam supercessions
V4s in the shop
More on V4 cams
Honda first-generation V4 bulletins
Ten things every first-gen V4 owner should know
V4 carb rebuilding service
V4 cam chain tensioners
V4 carb rebuilding how-to booklet