Strange cam chain guide shape

[Seabeowner]

Just stripping the top end off my 550K. The front cam chain guide does not look good at all. It appears bent to do the most damage to the chain. At the lower end it points forward and is worn through to the metal for the first 4mm. Along the middle section where the chain would normally contact the surface is mostly rough but not worn down. Any ides what caused this?
The actual tensioner blade at the rear shows very little wear at all. So at least it is cheaper than replacing this. (unless anyone has a spare?)
The bike shows just over 20k miles and am pretty sure never been apart.
Pictures show an old worn guide from a CB500 at top and the guide from the 550K at the bottom.

[Trigger]

This is due to someone not locating it correctly or putting in upside down.

[Seabeowner]

I presume that the spacing between the pins is slightly greater than than the spacing in the engine block and that it should bow out at the centre against the chain when all bolted down. This one must have somehow bowed in the reverse direction. As I say I believe it is as it left the factory, but it's nearing end of production in 78 and maybe assembly was not by their best workers.
The very worn one of the 500 shows no contact at all at the bottom 5mm and thought of bending the one off the 550 the same way, but the overall surface also has deep cracks.

[Trigger]

No, there should be NO bow on that guide. That guide faces to the outside/front of the engine.

[paulbaker1954]

Agreed,
It's a bit illogical how it fits IMO.

Firstly it  should be marked "TOP" so that way is easy but then the timing chain runs along the FRONT of the guide. I fitted mine the other way around so the guide was pushing the chain towards the crank. Then I couldn't understand how I couldn't get the timing chain around the cam sprocket as fitting this way effectively shortens the chain.

Easy mistake to make 

[Trigger]

Had a 500 four in last week for a rebuild, fitted the cam blade correctly, fitted the tensioner correctly but, could not get the chain on the sprocket. Decided to count the links and it was 84 links  , instead 88, that was a head scratcher. Never believed the packaging.

[Seabeowner]

Hadn't realised how flat they are meant to be, but I did fit a new one some years ago. Both those shown above have UP on the back. And both came out very bent, but in different directions.

[matthewmosse]

They can be tricky to get seated at the bottom end and if not seated right they bend when you tighten the head on, sheer luck which way they bend. Either way, its buy a new one time.