Yamaha would like you to believe these are sealed units but for less than 6 quid yours can be as good as a new one.
Firstly you need to buy the two new seals & a gasket
You DONT need the top right one 06108
Here's a diagram of the pump
First undo the nut, remove the washers & shim stack, then undo the small guide bolt the adjuster wheel bears against. Lift these off with the spring.
Undo the 4 screws & jently prise the pump apart. Inside you will find the two seals, note which way round they are fitted then hook them out & replace with the new ones. Clean off any old gasket & re-assemble in reverse order.
It is also a good idea to take off the outlet pipe nipples as these house the non-return valves. To remove grip with a pair of pliers & pull gently with a twisting motion. Inside you will find a spring which is usually full of fiberous crud & a ball bearing, clean off the crap & re-assemble, once nipple has been pushed home in correct position give it a tap with a pin hammer to lock it into place.
When re-assembling into the bike make sure the the washer on the end of the worm drive shaft is in place.
If the drive shaft is removed from the bike, now is a good time to check the shim stack clearance. This is done by turning the drive shaft with your fingers until the pump is at the top of it's stroke then using feeler guages check the measurement between the washer & pump cable wheel. If it is not within tollerance you will have to either add or remove shim washers. Some of the sizes are no longer available so you may have to remove all the shims & create the clearance you need with the shims that are still available . I think it's the 0.3mm ones which are NLA