CB550k1 US Import - UK registration

[Bryanj]

If you are going racing or want a daily commuter look for another, if its going to be used like most of us it will last for decades, seen worse running and left them in.
Dont forget if you get a new or reground you should replace or reface the rockers

[McCabe-Thiele (Ted)]

I would be looking at the appropriate rocker where that mark is  - looks like number 4 cylinder outside lobe? to see if there is any obvious corresponding wear.
I know little about what would have caused such a mark if it was a foreign object or a breakdown in the hardening from oil starvation.

As Bryan has said if the bike will be little used I think it would take decades for it to become a problem.

[juitz]

Thanks guys, this is going to be a weekend / fair weather bike so will stick with the current shaft.

Rockers look decent, but there are marks on 2 and 3 exhaust rockers.

[Laverdaroo]

See, told you I was no expert

[Bryanj]

Check if the rocker shafts have oveled the holes in the cover

[juitz]

Check if the rocker shafts have oveled the holes in the cover

Hi Bryan, could you clarify a bit? Not sure which holes to check 😋

[juitz]

See, told you I was no expert

All good Roo, to be fair I was leaning the same way which is why I posted 😃👍

[Oddjob]

The holes the rocker shafts go into, doesn’t usually happen on the 550 as the shafts are pegged and all one piece but on the 500 which doesn’t have them pegged and are in 2 pieces it’s been known for the shafts to spin and wear the holes in the camcover oval.

[Bryanj]

There is a service bulletin about it in the 500 ones in alladins cave but what it is the rockers pivot on shafts in the cam cover and those shafts can spin wearing th e shaft holes in the cover oval allowing the tappet clearance to wander so slide the shafts out and check the cam cover, the later K3 covers had a mod with cotter pins holding the shafts

[Orcade-Ian]

My 550 F1 USA with engine number starting 112 still has the two piece shafts (one for each rocker arm) and no pegs. According to CMSNL parts list for USA 550 F1, change point was after 113 something. 

Ian

[Oddjob]

Odd Ian as even the later 500 engines were changed to the single, longer type shaft but not pegged.

Clearly the fault didn’t rear it’s head in time for the change to be universal for the 550 engine.

[Orcade-Ian]

Ken,
After reading yours and Bryan's posts, at first I just thought that the immaculate (inside) cam cover i've just tidied up was perhaps a NOS one from a 500 - anything is possible in 47 years and probably multiple owners.  Then I did the check on CMSNL and found the change point and the fact that 8 shafts are needed.

Ian

[Orcade-Ian]

Thinking outside the box - with a bit of careful depth mic measuring, perhaps I could make a couple of copper or aluminium discs to fit on the end of the outermost shafts to have the 'o ringed' pegs on the outer covers push against the shafts to prevent rotation.  Returning to being sensible (rare, I know!) - I won't be riding up and down the M6 on a daily basis, so will probably not wear out the present setup!

Ian

[Oddjob]

There was an alternative method of pegging the shafts Ian and that was to drill down under the circles where the pontefract cakes fitted and use a self tapper drilled into the shaft. Not ideal but better than nothing. Of course this was used on the longer type not the 4 shorter ones, the 500 changed the shafts to 4 long ones before the end of the run but they weren't pegged.

[Orcade-Ian]

I might have a look to see if a Thackray washer is available to fit in the space available - maybe there is no space anyway.

Ian