For mountains the choice should be simple, a 2 stroke. They are more suitable because,
- They weigh less. Weight is a major problem on mountains and unpaved tracks. Lighter bikes are easier to handle. GS 150weighs 119 kgs and Deluxe around the same making them unsuitable for offroading.
- Engines are more powerful. In 2 strokes every other stroke is the power stroke allowing them to produce more power.
- They are simple, so easy to maintain.
- They produce much more torque and that also at low rpms.
- They have excellent power to weight ratios.
- For a 4 stroke bike to give comparable service the displacement should be more than 350cc.
Currently 2 brands of 2 stroke bikes are available, Yamaha YB100 and Suzuki Shogun100. Both are excellent machines but Suzuki Shogun produces more torque giving it fantastic pulling power but it is more expensive. Yamaha has advantage of easy availability of spares. Both weigh around 80kgs,
My choice would be Suzuki Shogun,