550K1 - intake valve rocker arm issue on cyl#1?

[Erny]

Engine - CB550K1 / 1975

Today during break in ride I discovered cause of oil leak - tapper cap on intake (cyl#1) was not tightened fully (strange as I'm sure I tightened it after tapper adj.)
But why - because valve arm is "hitting" cap and making knocking noise

I did not have tappet feeler gauge with me, but just checking free play with hand it looked OK, maybe bit too much.
Comparing with intake on cyl#4 it is obvious that tappet adj.screw is "too deep", consequently arm too high and hitting cap (and also nearly hitting cyl head cover...)

See attached pics for comparison, incl. "hammered" points in cap

===>>>  Can someone provide idea what's wrong, why this tappet arm is so high? Worn arm? Worn cam? Or some other issue I should look for?
I'll check other tappets too, but seems only this one tappet/arm has this issue (I did not realised it before when adjusting tappets). Motor has not been opened yet from stock.

Note: Temporary I filed part of tappet cap (wide groove) to allow free arm movement, I still need to arrive home tomorrow (>150 miles), hope it will be fine like that. I'll check tappet adjustments tomorrow on cold engine before I go.

[Johnwebley]

Both my Hondas can do this.

It's to big a gap and high revs.

It's safe to ride.

But check the gap

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[Erny]

This is what I'm afraid off - that there will be more damage, oil linked...

[Trigger]

This can happen for few reasons. I have found this many times due to :

Aftermarket tappet cover. Swap with another cover on the bike and see if it still does it.
Tappet cover over tightened with old 0 ring. New 0 ring and don't over tighten.
Worn rocker
Worn cam shaft
Tappet chipped 

[Bryanj]

Could also be hardening gone on tip of valve so it indents and you have to screw adjuster father in, short valve stem on pattern valve.
Those would not cause hitting of cap but that is problably pattern cap not quite right, seen a few of those.
If all parts original most likely cause is cam lobe/rocker pad wear

[Erny]

Won't know until you investigate but aside from time it doesn't really cost much to whip the camcover off.

I suppose removal of camcover can be done with engine in frame, right?

[Erny]

This can happen for few reasons. I have found this many times due to :

Aftermarket tappet cover. Swap with another cover on the bike and see if it still does it.
Tappet cover over tightened with old 0 ring. New 0 ring and don't over tighten.
Worn rocker
Worn cam shaft
Tappet chipped

I don't think it is aftermarket cap. Just checked now all other tappets and confirmed that only screw on intake cyl#1 is deeply screwed in like that.

New O ring would help just little in this case (yes, O rings are old, most probably stock)

As engine "eats" oil too (but no visible smoke from pipes), I'm afraid that engine rebuild is in front of me anyway (winter project)

[Bryanj]

Yes you can take rocker cover off in frame, and all way down to base gasket as well.
READ CAREFULLY all the warnings on this site and in manual about refitting cam cover