My left radiator/low temp switch/material falure - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 9 (permalink) Old 06-14-2012, 03:28 PM Thread Starter
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My left radiator/low temp switch/material falure

Well, my Left Rad is a victim of the notorious failure near the brackets. One leak by each bracket. The bike went down on the left side before I bought it. The top row was bent down just enough that you could kinda tell. The very bottom row was still straight.
Last year, at about 20K miles, I installed the low temp switch in Picture 1. This year, at about 24K miles, that rad started to leak. At both the top and bottom rows and right next to the bracket.

I'm suspecting some electrolysis between that brass(?) switch and the alum radiator. Picture 2 shows the OEM switch made of a different material. What, I don't know. Maybe someone here does. Sorry the picture doesn't show, but the OEM plug is very silver. no gold metal anywhere.

I'm suspisious because I ran the bike from 16K miles (right after the lowside) to ~20K miles with the OEM switch, and zero leakage from the rad all summer and hot weather. And my bike regularly saw 220-225F. At ~20K miles, I installed the switch, and Engine Ice. About 4,000 miles later, and hardly any hot weather in that span, the rad fails.

I had my favorite radiator shop try to repair it, he told me it was definatly material failure, and although he tried to epoxy it, it didn't hold.

Does anyone agree that the problem may have been promoted by using that brass switch in an aluminum cooling system?
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John, 2000 RC51 #000100

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post #2 of 9 (permalink) Old 06-14-2012, 03:57 PM
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In the one photo, it looks like a passage split near the damaged area around the mount tab.
May have to send Ben an email at RC51parts.com
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post #3 of 9 (permalink) Old 06-14-2012, 06:59 PM Thread Starter
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Yep. It did. I saw that and pointed it out to the rad repair shop. But he actually made it bigger during prep for the epoxy. It was just a sliver of a crack before. Both of those rad pics are after the repair.

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post #4 of 9 (permalink) Old 06-14-2012, 07:31 PM
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Forget epoxy. It won't work.
The previous owner of my bike punctured the left upper tank area, and then patched it with JB Weld.
It flaked off and that's when I found my leak as it was drooling.
I removed my radiator had it welded at a shop.
That was a much easier job than where yours is leaking.
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post #5 of 9 (permalink) Old 06-14-2012, 07:37 PM Thread Starter
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Originally Posted by SubSailor View Post
Forget epoxy. It won't work.
The previous owner of my bike punctured the left upper tank area, and then patched it with JB Weld.
It flaked off and that's when I found my leak as it was drooling.
I removed my radiator had it welded at a shop.
That was a much easier job than where yours is leaking.


The Rad shop told me it was a difficult position. And not just one leak, but two. This is the same shop that successfully welded my notorious SP1 leaking gas tank and many other unrelated repairs for other vehicles.

I guess I'm going to try to buy a new one, if they're still available and I can afford it...

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post #6 of 9 (permalink) Old 06-15-2012, 02:13 AM
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I had the same problem when I bought my RC.

Blew up the LH rad the same day I was ridding her home.

Bought a new one for $400 which blew up as well, 8 months later on a drag start with two GSXRs 1300 Hayabusha at a traffic light.

Both where cracked open underneath the upper mount.

I tried to find a Honda workshop paper, through dealer's network, that this was a common problem for the 2000 model RC's but no one knew anything about it.

Finally Ben at www.rc51parts.com saved the day.
He hooked me up with a full SP2 radiator kit for less of the LH rad's price.
So I drilled the required holes on my frame and installed them as you can see in my bike's thread.

Really sorry to hear that you have the same problem but the worse is that no one can guarantee you that buying an SP1 brand new one or a used one will be the last time you have to replace it


My ÷hlins Project: https://www.rc51forums.com/forums/showthread.php?t=6033
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Congratulation to MakisRC51 for winning the 2014 Bike Of The Year Contest!
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post #7 of 9 (permalink) Old 06-15-2012, 07:43 PM Thread Starter
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Good post, good points Makis. Thanks. More information to help me make a decision...

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post #8 of 9 (permalink) Old 06-15-2012, 10:05 PM
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Good post, good points Makis. Thanks. More information to help me make a decision...
It wasn't the easiest thing to me, to decide to drill my frame for the extra upper rear SP2 rad mount. I thought about it a lot and talked to a lot of people before I make a decision on that.
But in the bottom line, I was risking of paying for a new LH radiator and blowing it up again in the next 8 months or the next couple of years.
The RC builds up a lot of coolant preassure (1.1bar) and the radiators are quite thin skined so I believe that in high reving the vibrations are transfered to that upper mount causing the radiator pipe beneath it to tear up.
Usually factories correct their production mistakes on the newer models so when I found out that the SP2 radiators had that extra mount, everything was quite clear to me.
And when I drilled the frame, I found out that it has so many frame reinforcements inside it's tubing that there is no problem at all making that hole on each side.


My ÷hlins Project: https://www.rc51forums.com/forums/showthread.php?t=6033
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post #9 of 9 (permalink) Old 06-16-2012, 01:25 PM Thread Starter
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^ More good info. Like you, I would have been concerned about drilling the frame for that third mounting point.
It seems to me the SP2 did actually change some of the SP1 issues. However, some seem to be for racing only, such as the bigger throttlebodies, and the longer and flexier swingarm. But as well, some seem to be practical for street use too, like the extra bracing for the radiators, 2 fans instead of only one, and the judder spring and seat are a couple that I know of...

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