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Discussion Starter #1
Hi all,

I'll try not to waste too much of your time. I bought a $300 CX500 Standard at an auction this past Saturday and have been cleaning it up to prepare for a new project, as I'd like to have it mechanically sound before modifying it. So far I've taken care of a number of obvious things (ordered carb rebuild kit, will do ultrasonic cleaning on carbs, rehabing forks, cleaned air system, checked electronics, cleaned gas tank, bought camera to check cam chain tensioner, etc.), but I've heard from a number of individuals that the innovative (for the time) cooling system can cause problems on these bikes.

To be clear, I am not having any issues with leakage from the cooling system at all at this point in time. However, I have read that these issues can manifest themselves in a catastrophic manner that causes the impeller to wear a groove into the camshaft. Most of what I've seen online as far as threads go is people fixing cooling systems that had issues, but I am aware of the triple bypass/quadruple bypass that includes an exhaustive list of wear items such as the cooling system, cam chain related mechanisms, stator, exhaust gaskets, etc.

The jist of what I'm asking is: will any harm come from disassembling the bike and checking the condition of the mechanical water pump seal, impeller, and obstructions in the weep hole (if any)? I just want to make sure I'm doing everything I can to make sure this bike is in good running condition, but I know that these parts are sometimes best left alone unless they're being replaced, which I'd rather not do if I don't have to - and the bike isn't giving me any issues as it sits.

Here are the threads and documentation that I have referenced so far (I'm new so I can't link):

  • CX500Forum - Mechanical Seal - Diagnosing the cause of the leak
  • Motofaction - How to install the impeller - Honda CX500
  • Motofaction - How to install the water pump mechanical seal - Honda CX500
  • Motofaction - Where is the weep hole and how to clean it? - Honda CX500
  • Motofaction - Triple or Quadruple Bypass Parts List - Honda CX500
TL;DR: I don't want to neglect the bike I just bought, would it hurt to check all the parts in the cooling system or should I leave it be?

Any help or input you can provide is greatly appreciated!
 

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Let it be. If it is not leaking there is no need to open the system.
In general a failure in the cooling system is not catastrophic unless the warning signs are neglected. Warning signs such as over heating, coolant reservoir empty or overflowing, leaking from weep hole or from one of the water pipe o-rings.
Most important for these engines is regular oil changes, cam chain tension adjustment and valve lash adjustment.
You wrote "impeller to wear a groove into the camshaft ". The impeller is fastened to the end of the camshaft and even if it were to come loose it would not wear a groove in the camshaft. The bike would get noisy and probably start leaking coolant from the weep hole.
My dad always told us "If it ain't broke, don't fix it."
 

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Discussion Starter #3
Let it be. If it is not leaking there is no need to open the system.
In general a failure in the cooling system is not catastrophic unless the warning signs are neglected. Warning signs such as over heating, coolant reservoir empty or overflowing, leaking from weep hole or from one of the water pipe o-rings.
Most important for these engines is regular oil changes, cam chain tension adjustment and valve lash adjustment.
You wrote "impeller to wear a groove into the camshaft ". The impeller is fastened to the end of the camshaft and even if it were to come loose it would not wear a groove in the camshaft. The bike would get noisy and probably start leaking coolant from the weep hole.
My dad always told us "If it ain't broke, don't fix it."
Hey, thanks for the reply! The comment I read on the internet about the impeller damaging the camshaft read as follows:

"When the water pump seals start leaking, you’re going to find that it’s impeller is on the end of the camshaft which makes it a very expensive part in the case of the impeller seals wearing a groove in the shaft. NOS cam/impellers are nearly non-existent and expensive when you can find them, having a machine shop repair the issue on one is expensive as well."

This comment is mostly what caused my concern. I will say that I usually agree with the mentality of "if it ain't broke, don't fix it", but I wanted to make sure that ignoring this potential issue wasn't going to cause me any bigger problems in the future.
 

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I'm of the IIABDFI persuasion too
The closest thing I can think of to that somewhat alarming warning is that the
oil seal inboard of the mech seal can wear small ridges on the shaft but its generally
not a fatal fault and most bikes just carry on regardless
 

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Discussion Starter #5
I'm of the IIABDFI persuasion too
The closest thing I can think of to that somewhat alarming warning is that the
oil seal inboard of the mech seal can wear small ridges on the shaft but its generally
not a fatal fault and most bikes just carry on regardless
Even if it is harmless, is there any way I would be able to tell that this is happening besides just replacing the seal entirely?
 

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If the camshaft oil seal were to fail you would probably get some oil out of the weep hole.
If the camshaft gets grooved it can be repaired using a redi-sleeve Redi-Sleeves | The Timken Company or
Speedi-sleeve SKF Speedi-Sleeve type of product.
 

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If you take the rear cover off you'll see if there's any ridging
and a new oil seal is advisable anyway while you're in there.
I'd at least be fitting a new cam chain and mech seal as well
unless I knew for certain they were almost new.
Good time to do the other stuff too.
 

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I'd like to know who said that and what they were referring to. I've never heard of anything like that in 20 years on CX related forums.

This will give you an overview of the service I recommend for anyone with one of these bikes who doesn't know how well it was maintained CX/GL500/650 Cooling System Servicing:
 

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Discussion Starter #9
Thank you all for your input! Here's a link to the guy who commented the advice on my post.

Chances are, unless I begin to have issues, I'll probably leave it be.

Also, thanks for that article Bob! Huge help, and I haven't seen it in my searches. Another thing to add to the list before I start my project.
 

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Quote:
"in the case of the impeller seals wearing a groove in the shaft. "

For a start, it's not the impellor seal, the mech seal does not bear on
any metallic surface let alone the cam shaft.
How can it wear something it isn't touching?

The way I read it, he is referring to the small grooves worn by the oil seal
I've probably seen these to a greater or lesser degree on every CX I had.
It has nothing to do with coolant sealing and it doesn't have to hold back
engine oil pressure.
It only has to hold back crankcase pressure to stop it 'breathing' out of the weep hole.
As long as the oil seal is in good condition it's not a cause for concern IMO.
 

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Discussion Starter #11
Quote:
"in the case of the impeller seals wearing a groove in the shaft. "

For a start, it's not the impellor seal, the mech seal does not bear on
any metallic surface let alone the cam shaft.
How can it wear something it isn't touching?

The way I read it, he is referring to the small grooves worn by the oil seal
I've probably seen these to a greater or lesser degree on every CX I had.
It has nothing to do with coolant sealing and it doesn't have to hold back
engine oil pressure.
It only has to hold back crankcase pressure to stop it 'breathing' out of the weep hole.
As long as the oil seal is in good condition it's not a cause for concern IMO.
Ok, that makes a little more sense. I obviously haven't dug deep into the bike yet, and my experience with the CXs is as limited as limited can be. I've worked on cars mostly, but I was having a hard time picturing what the poster meant when he said that. I'm still not exactly sure about the physical relationships between some of these parts, but I'm sure it'll make a lot more sense once I'm in there to service stuff.

Seems like my initial alarm was somewhat unwarranted.
 

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This drawing should help you understand what's going on where the camshaft passes through the engine's rear cover. There is a space between the oil seal and the mechanical seal so that if either seal leaks the fluid that gets past it will exit via the weep hole instead of being pushed past the other seal. The drawing doesn't show the impeller, which is held onto the splined end of the camshaft by an acorn nut, sealed with a copper crush washer.
The white part of the mech seal is a ceramic ring (commonly referred to as the "polo mint" because it resembles the UK confection) sits in a rubber cup in the back of the impeller and is pressed against a carbon ring to form a seal that can rotate.

 

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With that non issue out of the way.
One potentially serious issue I would want certainty over
on a new to me CX is cam chain wear.
Worn chains can 'thrash' and chew lumps out of the case and
subject the tensioners to a battering that leads to failure.
I don't mean worn out chains either
Unless I see a new, or bloody damn good chain, I change it.
 

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Discussion Starter #14 (Edited)
This drawing should help you understand what's going on
Yes! The diagram is a huge help for me - things are making a lot more sense now. Thanks so much for your patience, I probably could've self-served a bit better and found this documentation on my own; my apologies if these questions are overly basic and redundant to this forum.

From what other posters have stated, it seems that the only things that would be cause for alarm are:

  1. Oil coming from weep hole
  2. Oil in coolant, and vice versa
  3. Visual damage/wear to the oil seal upon inspection (which should yield the previous two symptoms, but may not if the weep hole is clogged)
Additionally, the flow of either coolant or oil from the weep hole would be a sure indication that one or both of those seals should be replaced?
 

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Discussion Starter #15
With that non issue out of the way.
One potentially serious issue I would want certainty over
on a new to me CX is cam chain wear.
Worn chains can 'thrash' and chew lumps out of the case and
subject the tensioners to a battering that leads to failure.
I don't mean worn out chains either
Unless I see a new, or bloody damn good chain, I change it.
My plan for the chain is to check its condition using practices described in this CX500Forum thread:

CX500Forum - cam chain dental mirror inspection

and also this Motofaction page:

How to use a dental mirror to inspect the cam chain - Honda CX500

Except I will be using a small camera in place of a dental mirror. If the chain has room left to tighten, I wasn't planning on replacing it. Should I reconsider?
 

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I'd suggest that you do the cam chain inspection as suggested, then adjust the cam chain tension then inspect again. That should give you a better idea as to whether you should drop the engine and open for inspection and possible replacement or leave it in the bike and get it running. If you plan to keep and ride the bike a lot, the conservative course of action would be to renew these parts at this time ( triple bypass ). That way you will have a known good system ready for tens of thousands of kilometers of riding.
 

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Discussion Starter #17
I'd suggest that you do the cam chain inspection as suggested, then adjust the cam chain tension then inspect again.
Good to know. I'll do just that as soon as I get the camera in the mail. I don't anticipate that this bike will go more than 1,000 miles per year as long as I own it, but I do want to make sure it's well taken care of. I'll check back on this post when I take a look. Thanks so much again for your help.
 
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