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· Registered
218 Posts
Discussion Starter · #1 ·
Original water pump wheels of the CX / GL series are no longer available.

The situation with the 650 engines and the 500/650 turbos is almost hopeless.
The second-hand market has been swept clean here. The impellers are only offered sporadically around the world.

A well-known problem is wear of the teeth on the 650 WaPu wheels or corrosion damage due to long idle times.

But I've seen worn teeth several times also at 500water pump impellers.

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...Maybe the impeller of the next engine, on which you remove the rear cover and want to change the WaPu seal, looks like this.

It's no fake! This wheel I've got with a 650 engine, I had to repair.

The upper picture shows the wheel before and the lower pictures show it after sandblasting.

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With the 500, there is a possibility that you can still get a usable one somewhere. With all other models, the chance of this is almost hopeless.

Because I have a CX 650 and several 650 engines myself, I decided to re-produce the water pump wheels for the 650 cc engines first.

In order to be able to manufacture the parts cost-effectively, we of course have to use modern technology.

I got support from Kay, an engineer friend from the CX forum, who measured the wheel and created a CAD drawing and a stp file for production on a 5-axis turning and milling center. Without this support, the idea would not have been possible.

The impellers were scanned and measured ...

... and the first drawings and 3D views followed

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The production of the toothing was a particular challenge, as there is no suitable tool and the production of a broach would have been far too expensive.

In addition, a subsequent correction of the tool would not have been possible and the risk of losing a lot of money would have been very high.

So we also solved this detail "our way". That means, we photographed, enlarged and redrawn the teeth of the hub and the shaft and created a file from this,
after which the teeth could been wire eroded.

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The result was so good that the teeth fits better than the original :D

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The wheels are made from a particularly suitable aluminum alloy.
To avoid cavitation damage, it was initially planned to polish the surface and / or anodize it to a hard or glossy finish.

But the quality of the first prototypes was so good that we can do without polishing and only have to anodize the parts.

The enthusiasm in the German CX Forum was so great that people also wanted water pump wheels for the 500 cc engine.

So now we manufacture the 650cc wheels an also 500cc wheels and those for the CX 500 Turbo.

Unfortunately, we didn't have a template for the CX 650, but if we het one, we also can do it for the 650 Turbo engine.

The photo shows a 500 wheel at the top, the 650 wheel at the bottom left and the CX 500 Turbo wheel at the right

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"It's a very nice fit", Paul Brodie would say now. :D

... There is still no seal under the cap nut. Theoretically you wouldn't need it either, but the wheels are delivered complete with an aluminum sealing washer to prevent
that the anodized layer could be damaged.

The original copper seal is not used here. Aluminum and copper are considered to be an impermissible material pairing. Although there is a risk that a galvanic element can form here, due to the anodizing is to be classified as low, I do not want to take this risk either.

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· Registered
1982 cx500tc turbo
206 Posts
Hi f104wart
That is nice work (y)(y)(y)(y)(y)
Now you have the base platform to create a Hi volume impeller for better cooling at low rpm
And more block pressure

keep up the nice work

TLD 🇨🇦 🇩🇰

· Super Moderator
'84 CX650E that is evolving into a GL500
19,753 Posts
This is good news indeed.

For those who don't know, the impeller for the 650 engine is a bit taller than the one for the 500 (the cover is also taller to suit), which increases the amount of coolant that the pump moves.
I'm not sure how different the impeller for the Turbo is but I would expect it to be taller again than the one for the 650 (I think that's what I see in the picture of all 3 versions).

Some years ago I failed to torque the nut on a 650 impeller properly and it came loose, causing exactly the type of damage to the splines shown in the first picture. The only replacement I could get was from a 500. Since I used the bike almost exclusively in cold weather I accepted the compromise that would cause.
It is nice to know that if it ever happens again I can get the right part for the engine.

· Registered
1,757 Posts
Could you use an aluminium crush washer under the acorn nut? These are readily available from automotive suppliers.

Any idea on a price for these items?

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431 Posts

· Registered
218 Posts
Discussion Starter · #8 ·
They are rare, but they do come up for sale occasionally: ...
50 GBP/70 $ for 140 gramms of scrap metal is a nice joke. 😂

I haven't given any thought to the costs and shipping to England or overseas.

I have no experience of how customs are handled.

If there is general interest, I can clarify and calculate that.

· Registered
218 Posts
Discussion Starter · #9 ·
I'm not sure how different the impeller for the Turbo is but I would expect it to be taller again than the one for the 650.
Hi Bob,

the 500 and 650 have the same outer diameter, but the 650 is 5 mm taller than the 500 (27 instead of 22 mm)

The 500 Turbo has the same height as the 650, but a larger diameter. It's 61 instead of 58 mm.

· Registered
218 Posts
Discussion Starter · #12 ·
The choice of material was made in cooperation with the development department of a well-known pump manufacturer.

For an electrical potential for the formation of corrosion, a conductive liquid is required between the metals.

Cooling liquid for aluminum motors is not conductive.

When installed correctly, there is no coolant in the area of the toothing between the ceramic seal and the sealing washer under the cap nut.
If you want, you can protect the toothing with ceramic paste to be on the safe side.

· Registered
467 Posts
This is good news. I did wonder if anyone might do this considering how scarse the impellers are getting, and therefore the price of 2nd hand ones going up..
I've been living off borrowed time with one of my engines. Almost completely stripped splines, but loctite and a good torque has kept it going for now..
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· Registered
3,363 Posts
Is the distilled water comment on the lack of anti corrosive properties when used alone or its inherent ph instability when exposed to air (eg unsealed drum)?.....or suggesting "waterless" coolant.....that might be another thread.....

· Registered
1981 Honda CX500 Custom
15 Posts
These look great. Are these at the stage for you to start taking orders?
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