Ah, you're an Aussie mate! Sorry 'bout that, there's not that many of us on this site, (which most of the regular posters are probably happy about, ha ha!) anyway, I "bum-drummed" you, in Australia, both the 1977 and 1978 models were sold here as F2's. Just like we never got K3/4/5's, we went K0, K1, K2, K2, K2, K6! (only the US had K3/4/5, and F0, we just went F1, in fact so did everyone except the US) Confused yet?
Anyway, the problems with the head are many. You see, by 1977 the CB750 no longer dominated the "superbike" market, it was heavier and slower than it's main competition, the Suzuki GS750 and Kawasaki KZ650, and the F1's, (at that stage the K series bikes had been temporarily discontinued) while technically a very good bike and argueably had the best engine of the lot, were not particularly attractive. (A bit like that chick that your sister wanted you to go out with, you know, the "homely" one with the "nice personality", ha ha!) Honda wasn't quite ready to release the DOHC 750/900 at that stage, so they did the best they could and extracted another 4 or 5 BHP from the ageing SOHC engine, by increasing the port sizes, fitting bigger valves, and replacing the cam with a wilder grind.
Trouble was, to make the bigger valves fit they had to reshape the combustion chambers thus reducing the compression ratio slightly, the valve tips were too soft and would "mushroom" and require constant adjustment, the valve giudes would get loose in the head and the additional strain on the valve train caused by the new cam and heavier springs would rapidly wear out cam chains, and in a lot of cases, the engines would expire quite early in life from either a broken cam chain, or a dropped valve, particularly if the owner wasn't big on regular maintenance.
Certainly my (beautiful) F2 was suffering from most of the afore-mentioned maladies when I saved it from certain death a couple of years ago, and I've got the remains of another F2 engine with some serious head damage caused by a dropped valve. Although I've seen similar damage on K heads, it's certainly more prevalent on the F2.
It's not all doom and gloom, the F2 was as quick as the DOHC Suzuki's and Kawasaki's, and was quite a sweet handler, with excellent brakes, and with those excellent Comstar wheels, can even be fitted with tubeless tyres! My first F2 had been very well looked after by a caring owner, so apart from fading paint and a cracked seat, was in excellent condition with no head problems, although these may have been remedied before I bought it. I only sold it because I got a bargain on a Suzuki GS1000S, which pretty much eclipsed the F2 in every aspect. If the bike you're looking at appears well maintained, and is not rattling (well, no more than usual) or blowing smoke, it's probably OK. If the head is on the way out you can fix it, but as I mentioned before, an F1 head and barrels (painted black, of course) will keep it nice and reliable without a dramatic drop in power. Cheers, Terry.
