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1978 CX500, 1980 CX500 Custom
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Discussion Starter · #1 ·
I thought I was at the end of the engine rebuild. I installed the rear case with new seals and mechanical seal. When I put the water pump impeller on the shaft there was not enough thread to install the cap nut. I have the thrust washer between the impeller and mechanical seal and a new sealing washer. If I remove the thrust washer there is sufficient thread to be able to torque to the correct amount. There is about .005" clearance between the rear of the impeller and the face of the rear case. Without the thrust washer I can feel the spring loading of the mechanical seal when I push on the impeller. With the thrust washer installed there is very little front to back movement of the impeller. Is there a down side to not using the thrust washer? Any other thoughts?
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Are you installing the same washer you removed? It's not hard to miss the existing washer and add a new one to replace the "missing" part.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Did you remove and replace the same 10mm thrust washer, or was it missing when you took of the impeller?
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Is the thrust washer fitting within the ID of the white ceramic disc? Not hanging up on the disc's rubber seat?
 
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1978 CX500, 1980 CX500 Custom
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Discussion Starter · #7 ·
Is the thrust washer fitting within the ID of the white ceramic disc? Not hanging up on the disc's rubber seat?
washer fits inside of disc. No inference. How much should the impeller be able to move from front to back when pushing on the mechanical seal?
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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1-2mm, maybe, at most.
Can you post a photo of the camshaft end, with the impeller and thrust washer removed?
 

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Looks normal. Some seals have a thicker ceramic insert. Can we see that?

I'll take some measurements when I lock the shed but there doesn't seem to be a problem there.

Though the cup has two protrusions. If the inner seal isn't aligned with it it may not want to push back.

EDIT - I don't want to contradict Randal here but my answer to your question about how far you should be able to push the impeller back is more than 2 mm.

When fitted the impellers face for the copper washer generally sits roughly flush with the end of the cams threaded section. Pushed back that face comes close to aligning with the end of the spline which is where it will sit when assembled. My answer aided by the ruler in your photo is about 6 mm total.

This may vary between brands of seal though.
 

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Discussion Starter · #11 ·
Looks normal. Some seals have a thicker ceramic insert. Can we see that?

I'll take some measurements when I lock the shed but there doesn't seem to be a problem there.

Though the cup has two protrusions. If the inner seal isn't aligned with it it may not want to push back.
Everything tightens up normally without the thrust washer. With the thrust washer installed there are not enough threads available to get the nut started and tightened.
 

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I'll make some measurements of a cam shortly.

I think the spline is 'square" - 10 mm long x 10 diameter.

Minus 2 for the thrust washer should be 8 mm exposed. If I remember correct.

Give me a little while.
 

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Spline length is actually 8.3 mm, so you should be showing 6.3 mm of spline.

Given the disparity is roughly 2 mm I would check for a second thrust washer as they are 2 mm thick.
 

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The image in post #9 seems to agree with that.
 

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Discussion Starter · #17 ·
The image in post #9 seems to agree with that.
This is interesting. There is only 6mm of spline. The thrust washer is 2mm. I really don't see another washer on the shaft. I don't know any history for this motor so I don't know if it has been messed with before. My question would be, what is the purpose for the thrust washer? Set preload for the mechanical seal? If so, if your spline is 6mm with the thrust washer and mine is 6mm without what would be wrong if I didn't use it and assemble. I know the impeller tightens up and does not interfere with the rear case. Motor rotates fine.
 

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Have a close look at the cam. Have a scratch around. Thrust washers hide.

Purpose of the thrust washer would be to offer a harder faced abutment to the impeller than the material the cam is made of. The washer seems to be hardened steel.

That's guess. The whole back of the cam is a separate piece to the rest of the cam and is an interference fitment.
 

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1982 cx500tc turbo
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looking at the picture
some times the washer rusted on to the shaft so tight that it stays in place and looking at the picture
It looks like the washer is still there

Take a pair of pliers and see if it comes off

just grab the washer ever so gentle
 

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Discussion Starter · #20 ·
looking at the picture
some times the washer rusted on to the shaft so tight that it stays in place and looking at the picture
It looks like the washer is still there

Take a pair of pliers and see if it comes off

just grab the washer ever so gentle
I agree. Looking at the picture and the cam it does look like there is a washer, and it is 2mm thick. It will not move and I don't want to damage the camshaft. Based on the dimensions I have seen I think I am going to proceed to assemble the water pump as it is, not adding another washer.
 
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