Your rear engine seal leaking? Don just send it to the shop, FIX IT!
Changing the rear engine seal. This is the seal in the back of the engine that connects to the rear drive shaft.
Part needed: 93102-30170-00 (Yamaha OEM)
Start by jacking up the rear end, and removing the wheels.
Basically you need to remove the two long bolts that hold the rear diff in place, so that you can slide the diff back. Problem is the lower A arm is in your way to get the one diff bolt out.
#28 is the two diff bolts. Notice how the rear bolt goes through the tabs where the A arm would be...
Remove both #14 bolts (or both #11 bolts depending on which way your diff bolts are in), so you can swing the A arm out of the way.
Now is probably a good time to unbolt the brake caliper.
I believe you have to remove both #12 bolts, then you can take the caliper off the disc and tuck it up to the side.
Now you can slide out both diff bolts.
On the drive shaft(#37) pull both of the long rubber seals towards the center of the shaft.
Now you can slide the diff back. The drive shaft is free floating, meaning with the diff moved back it should fall out, you can pull it out from the couplers. Keep track of the parts here, there is a spring holding pressure on the shaft, the long rubber seals, and a small rubber cap thing that pushes into the rear of the drive shaft.
Now looking at the back of the engine you will see the coupler, with a nut in the center (#16).
You need to remove that #16. This is the fun part, to start with its torque to 110 foot pounds from factory, and will probably feel like more than that to get off. There is no way to hold the shaft, so i decided to just put the transition in park.
Myself i just used a impact to get it off. Impact on engine components is not recommended, but can make this way easier. Your bike, your choice.
Now you can slide the coupler off.
You will be looking at the seal(#13). CAREFUL! There is no "stop" place holder to keep the seal in the proper place. Remember how far in the old seal is, before removing it.
Check that the seal you got looks the same as your old seal. Just because the part is new, does not mean its the right part.
Pry it out. Lube the new seal with a bit of engine oil and punch the new one in with a flat pin punch. Slower, make sure you don't go to far. Use a crisscross pattern.
Put the coupler back on (put some lube on the splines) torque the nut back on to 110 foot pounds.
Put the drive shaft back on, put as much grease in those splines and the rubber sliding seals as you can. Remember to make sure that little rubber cap is on it, and that the spring is in place. You may need a hand holding the shaft and getting the diff lined up.
Put the diff bolts back on. Throw the A arm back on. I used copper coat (any anti seize is good) on all the bolts. This makes them easier to get off in the future, and protects them from corrosion.
Throw the caliper back on.
When you are done, check and make sure the sliding rubber seals on the drive shaft are all in proper place.
You may have lost oil when removing the old seal, check your oil level.
Should be good to go. Good luck!