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Your question is a common one - a new biker seeking advice on their first large capacity motorcyle which is capable of RTW work.
The DRZ 400 is indeed a superb little bike but for your needs it will probably be underpowered and uncomfortable (cheesewire seat OEM)! Forget carrying a pillion with this bike. It is primarily a specialist offroad bike and will struggle on any other ground. If I were looking for a small 400cc RTW bike then this little gem would be top of my list. But you need to look at a better allrounder -
Well unsurprisingly I would urge you to look at the venerable XT series of Yamaha motorcycles - XT500, XT600 Tenere, XT600 Super Tenere, XT600E and finally the latest versions - XT660 and XT660 Tenere.
All the above bikes are capable of REAL hardcore RTW trips. Their simplicity and reliability make them a first rate contender compared against any other Adventure bikes including it must be said BMW's.
You simply won't find a better "Bang for Bucks Bike" anywhere.
You can still buy a good low mileage XT600E for £1,500 ($3,000). I challenge you to find a better deal - It will be very hard to beat in this respect. A similar good BMW will set you back at least TWICE that amount!
Depending on your intentions you may wish to look at the Tenere series of bikes which have adventure/RTW equipment fitted as standard (OEM). If you want to tailor the bike yourself then look at getting a standard XT600 or XT660.
If money is no object then go for a new XT660 Tenere which can be procured in the UK for about £4,000 ($8,000). This represents very good value compared to other models on the market. The only other new bike worth looking at in my view is the Kawasaki KLE500 which is a superb little bike capable of serious RTW work. Last June I noticed new KLE 500's being sold off cheap at UK dealers at £3,000 ($6,000). Now that really is a bargain!
Remember a single cylinder bike will never be able to compete with a twin cylinder bike on the motorway. A single is happy doing no more than about 60MPH all day whereas a multi-cylinder bike will easily do 90MPH all day. This is the only area where an XT might struggle.
So there you have it - The XT600E is in my view worth a good look as is the Kwaka KLE 500. If you really want to carry a pillion RTW then you need to look at larger multi-cylinder bikes like the BMW 1200G and KTM 990 Adventure but don't say I didn't tell you how expensive this will become!
Triumph Bonneville 800 (2004), Yamaha XT600E (1999), Honda XBR500 (1986).