what causes a worn rocker arm?

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when i did my valve clearances not so long ago (~2-3 months ago) i noticed that my camchain was pretty close to replacing - about 3-5mm until the tensioner was fully extended. so i knew it needed changing soon, but its wasnt making a slapping sound so i left it.

when i was going home the other day i noticed that i had a "tap-tap-tap" sound coming from the top end. i couldnt see the source of the problem initially, but i noticed that the tensioner was down to ~1-2mm so i ordered a new cam chain.

went to go fit it, and one of my inlet rocker arms looks like this...




what would cause it to wear in that place?

the camshaft seems fine and there is plenty of oil in the cylinder head, on the camshafts, and on the bearing surfaces so i dont think its an oil problem.

im going to replace the rocker arm, and ive read that a slack valve spring can cause this to happen by allowing the valve to "bounce" the rocker arm, if that makes any sense, so ill change the valve spring if anyone thinks thats a valid thing to do?

[RedexRobB]

Is this on the rhs of the engine? I seem to recall that some worn rockers have been on that side and the theory is its starved of oil while on the side stand.

That looks really worn to me so i would consider replacing. Im sure anything more than surface marking will require changing.

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left hand side, 2nd intake rocker from the left.

i have a new rocker on order, will probably order a new head gasket as well, and ill give all the valves a bit of a clean. i have a valve spring compressor that will make short work of them, ill also look for any damage to the valves/pistons, but if a rocker is worn it wont open as much, so all i will have been doing is slightly starving cylinder #1 of fuel so thats ok. the cam looks fine, ill put the new rocker arm on and new cam chain and see how it sounds, ill do the valve clearances as well, then in 6000 miles time when i do the clearances again ill lift off the intake cam and see if its wearing again, if it is, it will be new head time...

i should really check the clutch as well (the cable is almost at full stretch and ive no idea what condition the plates are in, but it doesnt feel good, so probably new plates, steels and springs to be on the safe side), ill also do an oil change and new filter while im at it,

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all sorted now, didnt even have to take the engine out of the frame

replaced the rocker arm for a used one in good condition (light surface marks like the other 15), and replaced the camchain and checked about 3 times that the timing was correct, fresh petrol and it sounds good!

so whats gonna go wrong next? ill need new chain and sprockets in about a year (will have done 2 years/10k by then) and the clutch is coming out soon for a full overhaul - gonna replace all the friction plates, steels, springs and clutch cable with OE items next weekend along with oil change and an oil filter change, then sort out my suspension issues if possible, and roll on summer!

[Rasta-ninja]

I had similar issues with my rockers with a toad load of wear on the 2 closest to the LHS, i had them replaced only for them to wear down again along with one of the exhaust cam lobes being rounded slightly as well, im thinking like Rob said its to do with oil starvation because the pump is knackered...? Since the left side is the furthest the oil has to travel....either that or a blocked oil way.... how has your engine been since replacing the rocker?

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cant be an oil starvation issue as i tested the oil flow of the oil-passageways and it was fine, and the ones at the very far left were in perfect condition. i think its minute bits of dirt acting as an abrasive coupled with possible flaws in the hard coating, i change my oil every 2-3k miles...but as the bike has dont 35,000 miles previously with no documentation i had no idea how it was looked after.

it runs as sweet as a nut now, no tapping sounds, just a happy engine.

my L3 track bike needed 4 replacing (more out of caution than any real damage) but they were spread across the length of the camshafts, not located to one end in particular. if i can get 2 weeks booked off work ill drop the engine, replace the head gasket and lap the valves in and clean out any carbon deposits...get it back up to near-factory condition.

[RedexRobB]

Another cause could be the running temp of the engine. If it runs too hot that can soften tge hardening which is what happend to my first zxr when the headgasket blew.

But more than likely it could be a maintenance issue. If it got that far without being noticed then chances are its wasnt that well looked after.

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Another cause could be the running temp of the engine. If it runs too hot that can soften tge hardening which is what happend to my first zxr when the headgasket blew.

But more than likely it could be a maintenance issue. If it got that far without being noticed then chances are its wasnt that well looked after.

thats a good first point, one i had not thought of. im the 12th owner of my bike, so im pretty sure it was ragged about before i got it, i also bought it as a CAT C as it had been binned.