The R80RT speedo was over reading. The RT in the real world would not be that much faster, especially lugging that fairing about. Perhaps an indicated 105mph with that fairing on.....probably 95mph really.
It does have more torque, granted. You would be able to keep up with your R65, but you would have to work it harder, by using your gears and staying in gear through much more of the rev range.
As mentioned above, pick an R100 engine from a bike that is the same age, and you will want the carbs, exhaust(you will still have to modify it) and final drive. Cheapest way to do this is to buy a suitable R100 and strip it. Flog what you do not need on fleabay.
If you are running a single disk up front - then you might be advised to add another. But if you have dual Brembos or ATE's even, then they are the same performance as the R100 Brembo setup.
If you like leaning over and scraping your cylinders on the tarmac, or your roads have alot of camber, then the increased width of the R100 engine might be an issue. height difference of an R100 to and R65 is half an inch. This is achieved by the rear shock length and the front wheel size. The frames, are very similar geometry. I think the swing arm is shorter on the R65 which accounts for the wheel base difference.
I have both, an R100 and an R65. I have just MOT'd the R65 cafe racer, so its back on the road. The R100 is standard naked setup with Euro Bars. Yes it does accelerate faster, but I would still prefer to be on my 65. And my speedo on the R100 is a lying b*st*rd (+10%). Whereas my R65 has gone digital.
However, in the UK you are advised to keep the speed limit in sight. 30mph above the limit is a custodial sentence and loss of licence - no argument.
So being able to do 100mph+ has just become irrelevent.
Have fun
