hello, i have this 98 300ex with a new top end. i believe the rockers looked a little flat when i had it off before and it tapped loud then but ran good. today 3 minutes into a ride i was a little hard on it and all of a sudden it started cutting out and i heard a loud tap. i was going pretty fast then.it revs up fine but i tried not to blow it up. it still ran and no smoke either. i limped home. it even made the exhaust a little louder than normal. it is definantly coming from the valve cover. i think i may have broke a rocker or flattened the cam. anybody think they can help me here.

 

I bet that you or some one changed oil and put the oil fitler in backwards. then it won't pump oil up to the cam, very costly to repair, new head ect.

 

no that's not it. i got plenty of oil because there is an oil leak up there and it gets blown out.

 

if that was the case it would have done it a long time ago since it has had the same filter since i got it 9 months ago.

 

Ya; take the valve cover off and see what's fubared with the valve gear.

 

well about a month ago, me and a buddy took apart my 400ex top end to tighten things down and tighten my head bolts,we have done it a thousand times and for this process you have to take the cam out, we have gotten prety good at making sure the cam is in the right place (TDC), so without even thinkin about it we put the whole bike togather without a test fire, when we fired it up there was a loud noise coming from my valve cover, we were sure the cam wasn't off at all on the marks, so we checked all my valves and such and they were fine, but after doing all that it still was making the noise, so we took back of the valve cover reluckdently telling each other there is no way the cam is off, but after looking closer we decided to move it back a tooth and once we did it, it looked the same maybe a lil better, but thought there is no way that would be causing the nois and low and behold its amazing what one tooth does. so we put it all back togather and fired it up and the sound was gone. tis may not be yur problem but its worth looking into! hope this helps

Wreckless

 

ok i got it fixxed. turns out that something made the rocker just let go all of a sudden. i think it flattened more or something. i adjusted it back and now it doesn't make a hint of sound and runs good.they were very loose.