Bogging when accelerating in top gear

[will3hawks@xxxxxxxxx]

Just picked up a 94R1100RS. Bike runs smoothly, provides good power  
and gets aproximately 47-50mpg. Slightly cold blooded but this goes  
away quickly. When warmed up it ticks over at aproximately 900-950rpm.  
The only glitch is that sometimes when cruising in 5th gear and  
rolling on the throttle hard is that it bogs. If I pull in the clutch  
and crack  the throttle it revs quickly and cleanly. Any help as to   
where to start would  be appreciated; (the bike has 51K on it and has  
been  well maintained.

Many thanks,

Will