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1981 Honda CX500
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Discussion Starter · #1 ·
Hey all,

Hoping for some help, again.

First of all, I finally have the bike running good! It did not run and sat for about 7 years at a farm (outside) and exposed to all the elements. This being my first motorcycle that I’ve tried to bring back to life, I’m ecstatic.

Thanks to this forum and the help, and parts (thank you Murray).

My only issue now is the leak. Even though I did the quadruple bypass, I thought it was the mechanical seal even after completing the bypass. So I went through and pulled engine enough to get the rear cover off and replaced the seal again, used a new copper washer and new acorn nut, new thrust washer. The leak is not as bad as before when it sits but there is a nice steady stream from the weep hole when the bike runs.

The only thing I can think of is I might have not torqued the acorn nut enough. from memory. it’s 6 - 9 pound feet but I might have been on the lower side of the torque value of fear of overtorquing it.

any other things I can double check or silly mistakes anyone has seen or heard of?
 

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A leak where the water pipe enters the water pump housing can look like it is from the weep hole.
 

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Instead of using O-rings get the seal from a CX or GL 650.
 
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1983 cx650c
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The 650 ring is squared not round. It may not be recommended but when I put that pipe together I put a small amount of silicone rtv on rings and carefully assembled, making sure rings didn't get displaced. I waited a couple days before filling with coolant and starting,, no leaks.
 

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1983 cx650c
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Correction,, only one ring on that pipe, other end is hose and clamp. The other tubes on thermostat housing have orings on both ends and I used round rings and rtv on them and they're sealing well also.
 

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1981 Honda CX500
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Discussion Starter · #10 ·
Thanks all for tips.

I’ll try that seal instead of the rings. i had no clue there was a seal that could be used. looks like it may be part no 91315-MCA-A00.

Might look at using some rtv as well.i’ve got the black stuff and waterpump rtv somewhere. i think it’s blue or grey.

i’ve been using some plumbers putty to help it slide on but i guess it’s not clear what happens inside after the rings go out of sight.
 

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1983 cx650c
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I think the problem with using something other than grease is the possibility of pieces getting loose and messing with mechanical seal or something else. I didn't use much, just coated the seal with fingers and assembled. The hole the pipe goes in must be very clean and free of corrosion etc for a good seal. The 650 seal looks like an oring only square. It goes on the end, not between the two ridges on the pipe. Silicone grease probably works fine if everything is clean in the hole.
 

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Thanks all for tips.

I’ll try that seal instead of the rings. i had no clue there was a seal that could be used. looks like it may be part no 91315-MCA-A00.

Might look at using some rtv as well.i’ve got the black stuff and waterpump rtv somewhere. i think it’s blue or grey.

i’ve been using some plumbers putty to help it slide on but i guess it’s not clear what happens inside after the rings go out of sight.
I wouldn’t recommend using rtv. Which ever you use, the o ring or the 650 seal, they are adequate in sealing. Use silicone grease to help with installation and it won’t hurt the rubber. Clean parts are important.
 

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1983 cx650c
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As I recall when shining a light in the hole there is a reduced diameter with a lip the ring/seal gets compressed against when the clamps are installed. The end of the pipe goes in the smaller diameter and the ridge on the pipe pushes against the seal and expands it slightly to form the seal. The lip area must be very clean, the entire hole actually. I used very fine sand paper and steel wool but I had the water pump housing off so could inspect as I worked and clean thoroughly.
 

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'84 CX650E that is evolving into a GL500
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Note that the o-ring is supposed to go on the end of the water pipe, not between the ribs. Some people prefer to put the o-ring into the hole and then push the end of the pipe into it.
Note that you should use the silicone grease sparingly and only on the side that has to slide so that the rubber on the other side can resist twisting.
 

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Lost of varying methods described a point to note....Interestingly when I looked at using the 650 seal there did seemed to be some difference of opinion on how that seal was orientated... the "tapered end" facing out (towards the bulge in the water pipe), works....
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Note that the o-ring is supposed to go on the end of the water pipe, not between the ribs. Some people prefer to put the o-ring into the hole and then push the end of the pipe into it.
Note that you should use the silicone grease sparingly and only on the side that has to slide so that the rubber on the other side can resist twisting.
I find it works well to grease the receiver in the pump cover, not the o-ring. Then, the o-ring won't be lubricated vs the pipe and less likely to slip out of place.
 
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1981 Honda CX500
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Discussion Starter · #18 ·
I guess it’s some comfort knowing I’m not the only one who has had to fiddle around with these o rings on the water pipe.

Ty Sidecarbob for the tips. I tried an o ring on the end and between the nubs at the same time but seems they both moved. I’ll be trying again until I get it right.
 

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'84 CX650E that is evolving into a GL500
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I have usually used 2 o-rings in the past (since they fit all the water pipes on both of my bikes I bought something like 100 on eBay and it worked out to a few cents each) but I didn't realize that the seal for the 650 was different (even though the dimensions of the piper and the port are identical) so I think I'll try using the seal for the 650 next time.
 

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Not to be a broken record but the parts need to be very clean. I also agree with no silicone grease on the water pipe and just a little around the outside of the o ring. You are right that many people have had problems with this before but it isn’t very difficult. When I did mine I was expecting to have problems because of what I’ve read on this forum but mine slid right in the first try and never a leak.
 
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