What does this bolt do?

[MarkShelley]

I had a slight oil leak which I traced to an awkward to get at bolt. It goes down into the top at the rear of the barrell very close to the crankcase and can only be got at if you remove the throttle body. This was on the left cylinder by the way. You can`t get a socket on it because there is insufficient clearance to the underside of the suspenion wishbone. There is just enough space to get a spanner onto it with just enough movement to be able to nip it up which cured the leak. It looks like it has an ally washer on it.
What does the bolt do?

 

[(RIP) Mark H]

Thats the cam chain tensioner, change it for a later R1200 unit to get rid of the start-up rattle, it is just a tensioner, and no adjustment is possible,
The later 1200 one is the only one available now and does not drain oil so easily so retains tension on the chain, thus no rattle, its a good mod and not difficult to do. I have done it on my R1100, you can tell if it has already been done if the spanner size is 15mm, The old one is 17mm

Here is a very good write up about it;

http://www.ebbo.org/stop_the_rattle.php

 

[DrFarkoff]

cam chain adjuster

Part 10 in diagram

You Need oone of these

 

[MarkShelley]

Thanks chaps. As it doesn`t apparently do any harm having the rattle at start up I think I will save the £50 for parts for something else.

edit...reading this again, I am pretty sure it was a 15mm spanner so it must have been done already. Result!

 

[MarkShelley]

Just a little update/tip re removing the tensioner.
I recently bought an 1100RT cheap which needs a few things sorting, one of which is the rattle for a couple of seconds on start up. I have a new 1200 tensioner on the way and today removed the existing one. Somebody had already had a go and by the looks of it had attempted to loosen is by hitting it with a screwdriver and hammer! It was very tight. I don`t own any weird shaped spanners, but managed to do it by using a 3/8 drive 17mm socket and the small adaptor piece from my socket set that you would normally insert to reduce the drive down to 1/4". If you only insert this piece partly into the 17mm socket there is enough of the box section showing to allow you to get a thinnish 10m open ended spanner on. It worked a treat and a sharp tap with a lump hammer had it loosened. Because this method effectively raised up the leverage point it was possible to do this without completely removing the throttle body. I just unbolted the two bolts into the cylinder, disconnected the two electrical connections, slackened off the jubilee clip nearest the air box then twisted the throttle body and slid it partly into the airbox. The throttle cable slack as the butterfly opened as I twisted it gave me just enough clearance. The paperclip trick worked a treat. I will use the same method in reverse with a 15mm socket to fit the upgraded part.