I'd rather opt for later 1100s than early 1150s.
Look around UKGSer.com - where I've noticed most of the 1100 owners prefer 5 gear box rather than 6 on 1150s after ridden each. Saying 5 geared box just "feels right" and makes it easier to ride. In fact the long 6th is a bit of an overkill - owners say you'll reach top speed in 5th on 1150 rather than 6th which is just long "underpowered" (overdrive) gear marked as "E" ("economy"), but ironically it's fuel savings are very minor compared to 5 geared 1100. Fuel consumption is nearly identical between 1150 and 1100 looking at the specs where BMW is very precise compared to jap makers for example. Also the top speed of 1100 is faster than 1150 while having 5 horsepower less - this says a bit about the gearing on 1150.
Some say 6th is nice for highway low-rpm engine cruising ("smooth-stressless" ride). I've done all day comfortible 150-160kph (100mph) on my 1100 where it silky-smoothly sings at low (for that speed!) 5000rpm range and with two up full of luggage it has enough additional power for taking over cars.
1st gear is longer on 1150 which makes shorter geared 1100 a bit more confident on offroad riding, but as a payoff 1150 tend to have a bit better in city riding (takes longer to kick into 2nd). 1100 is 6 kilograms lighter than 1150.
I'm guessing 1997-1999 R1100GSes are one of the most ironed out GSes out there juding how long it has been in production and how hard way they've learned in that period from airheads->oilheads transition (gearboxes on airheads and early 1100s, corroding wheels, etc). Also it's strange to see later 1150 rust (bolts and fork bridge seems to be the main concern on 1150 users) so much in the wet condition countries like the UK while much older 1100s basically stay mint in the same conditions.
Anyways, I'm maybe too biased too as a 1100 owner. I reckon they're both superb bikes, but judging from the history of BMW models, where early models tend to have some teething issues, then me as a bit paranoid person on taking 'unnecessary' risks I'd rather opt for later model from previous version - a later low miler 1100 (1997-1999, while 1998 and 1999 being the best of the bunch) and save the spare dosh for some tweaks on it (i.e. aftermarket suspension, alloy panniers etc mods).
OR, put some more dosh and 2002 and on 1150, so they've had at least 2 seasons of running to "fix" their teething probs. It's all about how much "risk" can you allow and how deep your pockets are, as always...
Wondering if I was helpful at all or I just got it all more confused...? Margus
Last edited by Margus; 15 Feb 2008 at 21:44.