So recently on my VN750, the mechanical seal decided to fail, leading to coolant coming out of the weep hole. I have previously done work on cars, but this would be my first bigger motorcycle repair job, as well as first technical writeup, so if anything needs to be clarified do let me know. I did not see any good, detailed guides on the internet about motorcycle mechanical seals, so I thought I'd write one. Special thanks to
& a few others for any guidance on the way. So yes, coolant out of the weep hole under the right side of the bike is an indication of a failed mechanical seal, and apparently if it gets bad enough, the coolant will eat away at the ball bearing behind it. If you can see the ball bearings themselves, the bearing must be replaced. By the book, replacing the bearing would require removing the engine and splitting the case, but, there is a shortcut...
(Side note, if it is oil, and not coolant leaking from the weep hole, that is the oil seal and there is no other way to replace it aside splitting the case)
(This is what my ball bearing looked like, as you can see the orange seal in front of it had been eaten away, and came off when I sprayed brake cleaner in my original plan to replace just the mechanical seal)
So, parts needed:
Mechanical seal: 49063-1057
Impeller: 59256-1058 (for some reason the second half of the mechanical seal, the white "polo mint" only comes with the impeller)
9mm O-ring: 670D1509 (Goes on the impeller shaft)
19mm O rings: 92055-1308 (You will need four of these)
Ball bearing: 92045-1151
Cover Gasket: 11060-1090
Clutch Cover Gasket: 11060-1088 (Optional, if you feel like taking care of that while the entire right side cover is already off)
Lock Nut: 92210-0006 (On the impeller shaft)
Optional, but if you want to replace the radiator hoses now is a good time with all the coolant out.
PATIENCE. Do everything carefully, you don't want to cause additional damage to the motor. Cut/drill/hammer/tap with just enough force, do not rush or hit anything hard.
So, you may do this without putting the bike on the centerstand, I did this all on the side/kickstand.
1. Drain the Oil and Coolant. There is a drain bolt next to the weep hole (and maybe another one somewhere else, someone fill me in) to drain the block. You will want to drain the block and radiator. Tilt the bike with the underside drain bolt open (I failed to do this and had to drain coolant out of the crankcase).
2. Remove the 2 right side radiator bolts
3. Remove the right side exhaust pipe. You will want to spray a lot of PB Blaster/your fluid of choice on the studs, if they snap you will either have to drill new studs in or get a new exhaust manifold. Remove the 2 studs at the top of the pipe, and loosen the clamp near the muffler. This should allow you to move the exhaust pipe out of the way (I dropped the entire exhaust which may have been avoided)
4. Remove the rear brake pedal, unbolt it, then you can unhook it or let it hang somewhere else. Remove the right side subframe. You will have 4 bolts that require Allen/Hex keys to remove. 6 Bolts in total (8 including the 2 brake pedal bolts)
5. Start removing the bolts that hold the engine cover in place, try to remember where they go as they are different lengths. Unhook the lower radiator hose where it goes into the cover.
6. Hope you drained all the coolant, because if you didn't, it will pour downwards into the crankcase once you pull the cover off (happened to me, I drained it out the oil drain plug by pouring cheaper oil in with the drain bolt open to push it out)
7. Ok, so with the cover off, you will see the impeller. Remove the lock nut on it (regular thread, turn to the left to loosen) and pull the impeller straight off. It may have resistance, be careful not to damage the aluminum motor or bend the shaft when pulling it out. Remove the rubber o-ring on the shaft
8. Now the mechanical seal is exposed. You will have to pry it out from its seating in the block.
This video from another user on this forum (@Roach; )shows how the mechanical seal gets removed. Again, careful not to scratch up/damage the motor too much
9. Ok, so the seal is removed. Now, you may look in and see the ball bearing. If it still looks ok (like in the video) you may skip ahead to step 14. If your ball bearing shows the roller balls like mine, you will have to replace it.
10. So, if you look at a crankcase diagram, you can see that this bearing is actually pressed in from the outside, from your side of the motor. The case split is not done to put the new one back in, but rather, to hammer it out from the inside. However, as suggested, I experimentally (although I've seen this method only once on another forum) cut/drilled the ball bearing out to replace it. This took me several days of work with various Dremel bits (I still do not know what the perfect tool for this job is. The bearing shell is hard steel, and took a while before it would come apart and out) I had to cut the outer ring on opposite sides until it would crack. Same with the inner ring on the shaft, which I managed to thin on opposite sides, then tap LIGHTLY (so that the shaft does not get damaged or the c-clip on the other side doesn't crack open, because then you will need to split the case) for it to crack in half. I put rags all around the exposed parts of the motor to prevent as much metal dust as possible from entering the crankcase. You will want to be as careful as possible. Do not let your cutting tool slip.
11. Ok, so, if you drilled/cut the ball bearing, you will want to clean everything up as best as possible. Wipe metal away, etc etc...
12. Clean the impeller shaft. It will likely have corrosion & other deposits on it, so scrape it all off the best you can.
13. Put a slight amount of lubricant on the shaft (I used motor oil) and push the bearing on. I used a PVC pipe and a (10, 11, 12mm?) deep socket to lodge the ball bearing in. You will want something that fits perfectly against the metal rings, do not hit the orange/brown rubber sealing on the bearing. It might resists some on the shaft, it is a snug fit, but it will go in. Hammer slowly and carefully. Remember, there is a c-clip on the impeller shaft and if this breaks off, the case must be split. I alternated between using the pipe to hammer the bigger ring, and the socket to hammer on the inner ring. You will know when it reaches the end and bottoms out.
14. Alright, so if your bearing is ok/was just replaced, now we reassemble the mechanical seal. Use Emory cloth/very fine sandpaper to clean the area up a bit from any scratches during disassembly. Clean the area up well in order to create the best seal possible, get rid of any gunk/crud/corrosion, clean the impeller shaft. Use a 12 point socket (yes, 12 point. 6 Point will damage the seal) (I forget if I used a 1 1/8 or 1 1/16 socket. Use whichever one fits perfectly around the entire seal. The TOC manual recommends a 28mm socket. No matter what, 12 point is essential) and lightly tap the seal in. Every few taps, stop, and make sure it is going in straight. If it is SLIGHTLY crooked, adjust where you tap the socket/seal in order to straighten out. Take your time, if it goes in crooked/the graphite breaks, you will need a new seal. Stop every few taps and look from various angles to make sure it is pressing in straight. Keep going until the outer lip touches the block all around. If your seal comes with the blue stuff on it, you do not need any RTV/sealant.
15. Ok, so you got the seal in. Now, apply some antifreeze on the graphite ring and the polo mint on the impeller for initial lubrication. Put the 9mm o-ring into the groove on the shaft, and put the new impeller on. Tighten the new lock nut to 69 in/lb
16. Clean up the cover and engine block for the new gasket. You might want to use some gasket tack (I used blue rtv) to keep the gasket in place when putting it back on. Replace the 4 o-rings (2 on each side) on the coolant elbow that goes into the cover. Place the cover back on the block. Tighten the cover bolts to 87 in/lb. If you don't remember where they all go, hand threat the longest ones in first, if they do not bottom out, well, they go somewhere else. I'd give a day or so to let any sealants settle.
17. Reassemble the subframe/pipe/pedal.
18. Well, you should be all done now. Refill oil & coolant, fire her up. It might still seep for a quick bit as the mechanical seal settles in. Mine didn't. Assuming you did everything correctly and/or lucked out, you should now be ok.
I do not know why Kawasaki designed it like this but, this is a shortcut if you do not feel like splitting the case to remove the bearing. Had I the right cutting tool I would have probably gotten the bearing out a lot faster. I still don't know what's better to use.
Otherwise, that is how the mechanical seal gets replaced. If I missed any steps let me know. If this post is unnecessary, mods, feel free to delete