THINGS YOU NEED TO KNOW…
The design eliminates any sideways swiping motion experienced on the top of the valve, which occurs on engines with a conventional bucket and shim design. These buckets also have to be strong and, therefore, heavy. Rocker arms reduce this weight by between 40% and 50%, depending on the engine.
If you can imagine a load of buckets, which are 25mm across and 25mm wide, it’s quite a weighty item. Weight loss on the top of an engine is important because it helps the bike in its chassis development. By how much though so is hard to say.
Buckets of cash
This system also allows for a flatter combustion chamber, meaning manufacturers can run a wider bore. It also means that the inlet camshaft and inlet ducts are straighter and more vertical, which improves intake efficiency. Both the new Suzuki GSX-R1000 and BMW S1000RR use a finger follower (also known as a rocker arm) design in the top-end of their engines. Most engines still run a bucket system instead of rocker arms though. These arms also help reduce the drag within the top-end of the engine. Some factories look towards buckets over them because this system is less costly to produce. world
Another big difference between buckets and shims and rocker arms is that the arms help to keep the cylinder head quite a lot smaller. This is better performance-wise, as it makes the bike easier to work on. Personally, I find them easier when doing valve clearances, as it’s a nicer feeling when you put a feeler gauge in between a rocker arm and the shim, rather than trying to feel where you’re going with a big bucket.
This system is also better for power because when you’ve got buckets made of steel and then an aluminium cylinder head, you have two parts that display different traits when heated. Most rocker arms are made solely of nitrided steel, instead.