How old is the bike? The brakes need bleeding but if it still has the original rubber brake hoses these could be expanding. These need to be replaced about every two years. Save yourself some money in the long run though and get a set of BF Goodridge or Earls braided steel lines, these don't expand and last for years.
the bike has got to be older than 5 years as it was replaced by the 749.
4000 miles shows it has not been out for long each year in that time.
Brake fluid is hydroscopic in that it absorbs water from the air.If the bike has ben stored over winter say three in a row then the likelyhood of a lot of water being present in the oil is high.
Thus as soon as you get out on the road each year the first thing that happens is that the water boils out of the oil when you apply the brake.
This causes cavitation and a gas bubble in the brake circuit. then the brakes get lax and it is likely the calipers will stick and then the brake lever will become uneffective..
