Benneli the water pump aint **** to take out in fat it is just a impeller pum with a sealed bearing on it. If I was at home I would see if I could read the bearing numbers off for you. Easy to pull and change the pump.

Drian water and save if you want. Drain oil and save if you want. Pull the front pump cover off the pump. Pull the other hose coming from the engine block to the body of the water pump The one on the cover I just leave on and leave it attached to the radiator. Tie it out of the way. Since you pulled the tree bolts to ge tthe cover off the pump is unbolted already. Pull pum out and change or look at bearings in the back toget bearing part numbers. I would just buy another pum but I am lazy. The pump pull straight out it has a O-ring on it as a seal in the cover hole it fits into you might have to twist it a little to break her loose but is is easier then zipping up your zipper after taking a piss. Lube the new oring with engine oil and slide new pump in. while rotating it so the drive slot lines up the the tang on the oil scavenger pump. It wll not go all the way in till it is in the slot. If you pump locks up it could break the scavenger pump shaft. Not hard to change but you will feel stupid if you don't check the pump out and it seizes up. Mine did at 50,000 miles. And I had to put in a new scavenger pump do to not checking it out sooner.
Let me see if I can locate some pictures to help you.

In the picture below the engine is upside down but at 12 Oclock you can see the drive shaft for the water pump coming from the oil scavenge pump it has a tang on it like a large screw driver . it it what drives your water pump.


Here is one of the drive chain and sprocket that drives the oil pump and thus the water pump drive shaft
 
I know this is an old post but . . . how much slack should be in that auxiliary chain? I got my clutch off and still checking for what could cause my mystery noise. The chain has about an inch of slop to it and the bearing that is on the drive sprocket behind the clutch basket is sloppy. I can twist it within the sprocket. I need some input from one of you mechanical experts. :eek:
 
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