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 Topic: New Member with An MC18...wait.....no...an MC16...yes MC18 







Hudtm60
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Hudtm60 » Tue Mar 24, 2026 2:17 am

At last I finally got round to replacing the mechanical seal. I wanted to get it exactly right and so spoilt myself with getting some OEM Honda tools to make sure it went right.

Per the Service Manual


Got most of it...


Bearing goes in first.....so it got placed in the freezer for a bit to make it smaller and I heated up the casing to make it's prospective home a little larger....we're talking in mini micro amounts here...but I think it helps...


This bit, called the 'pilot' goes on the end of the driver handle...and centers the bearing...


and this outer part takes care of the outer edge...








Next flip the case over to the oil seal....not the greatest pic but you should see that the flat side faces out...


used a tiny tiny smear of Red rubber Grease to ensure it slipped into its permanent home with ease also but a bit on the inner ring of the oil seal where the water pump shaft will soon slide plunge through...


then this tool comes out to tap in the mechanical seal without any distortion....



mechanical seal has it's own strip of lubricant/sealant....


sits on here...


here comes the tool at the end of the driver handle...


..tap...tap...and it's in...


with all the bits assembled into the case, it's time to put it back on the engine...gasket first....it's still in good nick and a thin smear of rr grease is enough to hold it in place...


water pump shaft/gear goes into the motor....


but don't forget the washer....#16...which goes in FIRST...


Doesn't do any harm to put in a new waterpump housing o-ring...i just happened to have an extra...so I did it...



made sure that both the kickstart oil seal and the water pump oil seals were lubricated, slid on the case and torqued it up...


this is how this is inserted into the impeller...that white ceramic side meets with the mechacnical seal...some pundits say to put a bit of coolant on it so it's not completely dry when it starts up...seems a little pointless but did it anyway...make sure you place the washer in (#17 on the above parts list) within the ceramic spacer


this is a pic during disassembly to remind me about the washer...the impeller spins onto the water pump shaft and then it's a lot of boring reassembly of plumbing and bolting up the water pump casing ideally with a new gasket but mine was still good considering it was only on a few months....and then refilling the coolant....


a fresh washer on the sump bolt is always a good practice...


and my oil of choice is Motul Transoil 10w-30 almost certainly due to good advice acquired from this forum.


And long story short.....been running it around for about 200 klicks and it's dry as a bone underneath.....overall running good but at quarter throttle annoyingly very burbly and I've yet to focus on that ....it must be right where it's transitioning carb circuits so I have to study which variable I can..well...vary...

Note I've left off the inner piece of the bottom fairing to give me access to the front plug...always checking it's colour.




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