I sometimes drop down a gear or two when going uphill, and I have got a 1000cc bike!! So why not do it on a 125? Edit. In fact I can't think of one mode of transport where the need to drop down a gear isn't required at times From max revs (limited - see OPs comment) in 4th - drop down two gears and....... Pick yourself up. Pick the bike up and check for damage. Replace rear tyre, chain, sprockets and trousers! It depends on the gradient of the hill. Picture this, you are going up a hill in bottom gear (4th, 5th, 6th. Whatever) and the revs start dropping along with your top speed. Drop down a gear and as if by magic the revs start to rise again and so does your speed, this carries on untill you either reach the summit or run out of gears in which case you come to a stop. Simples!!