Oversize valves (33.5mm i/o 32mm) specially made for the CB 750 SOHC/4 are available from APE and Kibblewhite. Kibblewhite also has a conversion kit for 5mm stem valves (stock is 6.5mm), which are lighter than the stock valves. Manley and Yoshimura made special valves. Intake valves of the '78 F2 and F3 models are 2mm larger, but they are no longer available from Honda. Altough I have good experience with using '78 F heads, it is an issue among performance builders. Nonetheless, the combustion chamber of these heads is about 5cc larger which reduces the compression if it is not made up for with higher domed pistons.
F2/F3 valves are available from third party suppliers in improved design. For those who want even larger valves, Gold Wing valves may serve as billets.
Bronze or steel valve guides are available from APE, Kibblewhite and others.
As outlined in the cams section, there are two ways to prepare the valve train for higher revs, more valve lift and more radical cams. Stronger valve springs and a lighter valve train. The first puts more stress on the whole valve mechanism which means more wear and eats valuable ponys that will not make it to the rear wheel, the latter may lead to failure if e.g. rocker arms are lightened too much, and at the wrong place.
Stronger valve springs are available from APE and Megacycle. Web Cam lists two different valve spring kits along with aluminum and titanium retainers. Action Fours, Yoshimura and many others used to make them, too. A cost effective solution are the springs from '78 SuperSport (F2/F3) models, which are approx. 10% stronger than the earlier models.
Titanium retainers are available from APE, Kibblewhite and Web Cam. Action Fours had titanium retainers. Beware, the F2/F3 models not only have different valves, but the retainers and cotters are also different and not interchangeable with the other models. Action Fours had titanium retainers especially for the F2/F3 (and they listed the same retainers for the Kawa Z1/Z900, but I am not sure whether Kawa Z1/Z900 retainers are interchangeable with the F2/F3 in general). Titanium retainers save 4 grams (10gr. vs. 14gr.) over stock.
Stronger cam chains are available from DID (DID #219 gold on gold, used in kart racing) and Tsubaki (BF05M). Length is 94 links.
Cam Chain Tensioner
M3 Racing has a heavy duty cam chain tensioner. If you don't want to spend the money, try to find a cam chain sprocket from a CB 450 twin to replace the stock rubber wheel.
Adjustable Cam Sprocket
An adjustable cam sprocket is necessary to correctly degree your cam. Besides, am adjustable cam sprocket lets you adjust the engine characteristic by advancing or retarding the cam. They are available from Web Cam, but if you want to save the money, take a round file and file the mounting holes in a stock sprocket into curved slots.
Rocker arms can be lightened. As they are rotating around the rocker arm pivot, mass reduction is more effective the farther from the center it is done. In addition, the adjuster nuts can be turned down to half height.