Motorcycle News (UK) - - GARAGE -

Weight sav­ing

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

Big bucket

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.

Fin­ger fol­low­ers and shaft valve­fromabove,you­canseethe­valvespringsandfin­ger­fol­low­er­scom­bus­tion­cham­berands

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