R1200RS Cam chain tensioner tool.

[sanemancured]

If you're talking about the device that supposedly puts the correct operating tension on the cam chain so you can verify that the cam timing is correct (possibly using the BMW camshaft locating device 11 0 827), I wouldn't bother. I have the BMW locating device and was thinking about buying or making the tensioner device you are considering. I decided to try an experiment. 
First, I left the regular cam chain tensioner in place, and tried the locating device on the camshafts. It fit in place (indicating "correct" timing with limited tension). I then removed the cam chain tensioner and carefully used an appropriately sized metal rod to manually tension the cam chain to varying degrees. I found that no amount of increased tension, beyond enough to take the slack out of the cam chain, made any difference to whether the locating device would easily fit in place. 
In other words, if you check the timing with the regular cam chain tensioner in place, it will be correct. I guess the fact that BMW specifying the expensive cam chain tensioning tool for checking the timing is just normal German perfectionism.

That's interesting. I've read 2 details, including one from Boxflyer himself where using the tool to pre tension the chain fully has made a difference.

From memory in one case the locating device didn't fit until the pre tension was applied and in the other it did until the tension was added.

I was thinking of trying what you did and manually adding various amounts of force to the tensioner. I can't really see BMW designing and manufacturing a tool that seems relatively complex if there is no need?

I've managed to reserve one with the BMW Club UK. I'll report back

Peter