Vintage Dirt Bike Q & A

Everybody knows that the early Honda water pumpers corrode.

The 2$ question is how do we stop/prevent additional corrosion?

With Honda not producing anymore cases & the corrosion marching on, it is a matter of time when we will run out of serviceable cases.

I had Mylars clean my rads and I have cleaned out the rest of the system.[b][/b]

So whats the cure?

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

Well I JB welded the well under the pump and it works/doesn't leak also been looking for a replacement (case) with no luck... when you had your radiator work done did they cut them apart or just pressure clean inside in some way??. Will 81 and 82 cases worK??.

I also JB welded one case after grinding out with a Dremel. So far so good.

Not sure about the interchangeability between 81-82-83 cases. They are different part numbers but that doesn't mean they will not interchange.

Mylar's did not cut the rads apart. I can only assume they were dipped & then rinsed in some way. I had them clean & repair 3 sets. One set was clogged pretty bad & it came out squeeky clean.

There has to be some way to stop the corrosion. I just haven't found the answer yet.

Regards

Stan
WV
304-265-0670

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

Only use distilled water. That doesn't take care of the dissimilar metal problem (the real culprit) but helps some. If you could have one specially cast in aluminum, it would fix the problem, but I'm a dreamer.

Use of distilled H2O is a must. I have been doing that for years.

I wonder if..

A: frequent changing of distilled H20 & antifreeze is a partial answer?

B: The addition of Maxima Cool-Aid helps? (I use this at 10% by volume)

Oh, Mitchie, you can bet Da Vinci was a dreamer....

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

I'm just speculating here, but would there be some way to make a sacrificial zinc anode that could be inserted in the system somewhere and replaced annually. Since the real culprit seems to be galvanic corrosion, curing it the same way the marine industry does would make some sense. This way the zinc would sacrifice itself to the corrosion, leaving the expensive parts intact. I'm not a metalurgist (sic?), but I'd think that zinc would be a less nobel metal than aluminum and a zinc anode should work.

Wikipedia gives the following definition of galvanic corrosion, as well as a few ways of retarding it.

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Steve Amling

1976 CR 250M
1980 Yamaha DT100G
1980 XR 200
1981 CSR650

http://www.evanscooling.com/. These folks do coolants specifically for magnesium block racing engines. The other complementary route is to epoxy-coat the inside of the water pump so the case never comes into contact with the coolant. This approach is from the aircraft industry. I read about a coating in MXA and have emailed them for more information.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

I have heard of some stuff called Devcon that will work

http://www.devcon.com/ Devcon is both a company with products of the same name, and they make the Permatex brand. They have brush-on ceramic materials that will repair and seal corroded pumps.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Some great information here gents. Right now Devcon seems to be a way to repair and coat the impeller area.

Michael, have you tried the Devcon method, either the putty or coating? How did it work out if you did?

Inquiring minds want to know......

Keep the experiences and comments coming, we all need to find the
answer and put this corrosion to rest.

Regards

Stan

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

I had a '86 CR250R at one point where I saw this corrosion, but the bike was sold before I had to tackle it.

_________________
Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

I talked to Tech Support at Devcon today. From what he is saying, since their coolant contains no water, this takes corrosion out of the equation. Just what the doctor ordered.

I ordered a gallon today. Hope it works. Surely it can't hurt.

Regards,

Stan
WV
304-265-0670

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

UPDATE

I have been running Evans NPG for several months now.

Its the berries!!! No corrosion AT ALL.

One word of caution. It seems that if you have a poor fitting head or pump cover gasket you will find out with this product. This includes your water pump seal.

I will not run any other liquid in my vintage Honda's but Evans NPG. Great stuff!

You might be able to find it locally at your local dealer. Seems that some late model 4 wheelers are having the same problem as we are. The mfg. is telling all dealerships to use the Evans product in lieu of water/antifreeze.

Blue Skies

Stan
304-265-0670

_________________
83 CR250
83 CR480
87 YZ250
88 CR250
74 TY250
07 YZ250
83 RM250 on the resto table
91 YZ250 with an Ohlins 360 kit in resto que
83 CR125 in resto que

the 1981 1982 1983 water case are all the same the only differemce i know of is the outer impellor housing

This seems to be a pretty hot topic looking at all the responses to this thread, and many good ideas.
I would like to add one more suggestion.

If I understand the problem correctly, the corrosion problem is caused by a metal water pump housing
and impeller mounted on an aluminum engine case (electrolytic corrosion or galvanization from disimilar
metals). Am I right to assume no other component of the cooling system is problematic? That the
cooling system contamination originates and ends with the water pump?

The military has used a product for some time that is pretty effective at controlling this kind of problem.
Corrosion is a huge problem for aircraft at sea. Constantly spraying various alloys with salt water
wreaks havoc on them and corrosion control is a full time job.

There is a product available to the public that is very similar to what is used by the military.
It is a simple spray on wipe off coating that stops the corrosion at the site. Combine that with
a flush and clean of the rest of the cooling system as well as some of the excellent suggestions
to use wetting agents and DW, etc and you should be able to control , if not eliminate, the problem.

The corrosion inhibitor is available from this link if anyone is interested:
http://www.nocorrosion.com/cart/commercial.php

I don't have a horse in this race (my water cooled bikes came after this problem was rectified), but
I hope this info helps those that do.

Finally, if there is SIGNIFICANT interest in a cast aluminum version of the OE piece, I can reverse
engineer and produce an OE quality part. Cost would depend on volume required but should be in
line with the price of a Boyesen or Pro Circuit impeller housing.

I am starting a business (spare time at first) that will produce and market hard-to-find or obsolete
parts for vintage cars and bikes. I am trying to wean myself from my real job and eventually do this
full time. I have the capability of reproducing cast and machined parts in original or "enhanced" material.
No stampings yet, so no tanks or pipes. Let me know what parts you would like to see available again.
And by-the-way, everything will be produced right here in the good 'ol USA.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R