Most of the legend of f2/f3's having bad top ends comes from honda services techs back in the day, who saw a lot of these bikes with problems because, quite frankly like all new motorcycles a good deal of them were abused right off the showroom floor. Yes there is an inherent design flaw that will eventually lead to oil consumption
Top ends? Abuse? Eventual oil consumption? Man, this stuff is so far off the mark I can't hardly believe it. Do you have any idea of what was going on in 1978? When Honda revised the engine for the 77 model year, they took a trick from the Chevy builder's handbook and re-angled the exhaust valves to make room for larger valves. A similar thing was done to the 650 SOHC in 1979, and both cylinder heads suffer the same problem. The exhaust valve guides wear prematurely, very prematurely, as in 4,000 to 6,000 miles. I was there, both as a factory warranty analyst and at different times as a dealer tech. I have shared this before but the Honda rep for the L.A. area back then, Fred Germain, revealed to me that Honda responded to the problem by coming out with harder valve guides. You had to check the guides in your parts stock with a certain size drill bit, to tell them apart. The harder ones were so hard they were pre-reamed. The drill bit had nothig to do with drilling, just a sizer. Number 1 -- it isn't the whole top end, just the exhaust valve guides. The valves will rattle like a pencil in a coke bottle within an extremely short time if the exhaust guides are original. Number 2 -- Abuse can be blamed for a lot of things, on any product, and rightly so in many cases, but not in this case, not even a little bit. Number 3 -- oil consumption was the least of the rider's worries when the valve started moving back and forth in the guide 1/16 inch! Check your facts.
Below I have included two factory Honda warranty contact team (SWAT) log pages. One shows the F2, the other shows the CB650.
