I need to know if you can replace the rear cam guide with out removing the head. A freind of mine had a new chain,guides,and a tensioner in stalled last year and has gone about 1100 miles. since I have an 06 s40 an being a retired auto. tech. he thoght I could help. Any way I took the cover off an sure enough tensioner is out and spring is bent. He showed me the old parts and said both guides were changed how ever he only has the forward one and I don't feel the rear was changed. Looking the engine over I does not look as though the head was off. Also the metal is more discolored than the forward one. He did call the dealer and was told him they would do it over for the same price$$$$$$ as last time. They only cover repair failure for 6 mo. or 6000 miles. he won't go back.  Any thoughts?
        Viper
Ride on Ride safe
This is a 2000 650 12342 miles  stock no mods. 1st time chain replaced

Yes the rear guide aka tensioner can be changed w/o removing the head or cover.  I tried it with the cover off couple years ago.  And just walked someone else thru it last week.  You'll need to remove the primary gear for better access.  (yeah, that's the guy, dam speed typer)

Upon re-reading, they changed the chain?  can't be done w/o removing the cover.  I can understand not replacing the forward guide, it doesn't get as much wear and you have to remove the head.  Seems to me he got fleeced.  1100 miles on a new chain is BS.  check the bill, make sure he was charged for a chain.

Yes Verslagen 1 the bill has chain,2 guides.and tensioner. I do feel the chain was replaced I have the old one (well I have a chain may not be from this bike but I do have an old one) I have not checked it for strech yet but I will. I did see a thread on putting a slight curve in the rear tensoner. Is this wise? I also pushed the tension guide forward with slight pressure and I would say from insid to inside of chain ther may be 1/4" from each other thats getting real close to hitting its self.
Since it's in my garage I guess I'll go ahead and take it apart and see whats going on.
Thanks VIPER
Ride on Ride Safe

1st, I seriously doubt they put a new chain in.
2, 1/4" (6mm) apart? Are you sure? you can't get that close w/o an extention on the plunger.  Check the chain in hand, I bet they gave you the new one.  Sleasy basterds, I wouldn't let them check the air in my tires.

Now as far as the curve in the guide goes, only on a new guide would I do this.  The old ones crack with age.  Only one fellow has ever reported this plastic coming off, but that's enough for me.