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Thread: '92 K75S radiator leak

  1. #16
    As an alternate to "welding" the aluminum radiator with metal rods to make the repair I am considering using an epoxy material. Stik-Tite is a low melting temperature epoxy intended for the repair of aluminum radiators. I obtained some of this stuff and did another experiment on an aluminum can. This time I used a small butane pencil torch. I created holes smaller and larger than in my K75S radiator. The area about the holes was cleaned using the Dremel and stainless brush. The area was heated with the butane torch and I let the Stic-Tite melt around the holes. This was very easy. Afterwards the aluminum can held water (not at pressure).

    https://www.northernfactory.com/Product/Z12156
    https://www.amazon.com/Northern-Radi...1TNPPMG24STCQR

    stik-tite on small hole-1.jpg

    stik-tite on larger hole-1.jpg
    Last edited by robsryder; 01-22-2020 at 01:53 AM.

  2. #17
    Since the root cause of the leaking radiator on my K75S was the plastic fan walking forward on the motor shaft I decided to fix the issue so that it wouldn't happen again. I used a 3/32-inch drill bit to make a "wallered out" hole ithrough the nipple of the plastic fan. This allowed a stainless steel cotter pin to be placed through the hole in the plastic fan and motor shaft. The small red dots on the top of the shaft were to help me with alignment.

    k75s rad fan secured to motor shaft-1.jpg

  3. #18
    Quote Originally Posted by robsryder View Post
    Since the root cause of the leaking radiator on my K75S was the plastic fan walking forward on the motor shaft I decided to fix the issue so that it wouldn't happen again. I used a 3/32-inch drill bit to make a "wallered out" hole ithrough the nipple of the plastic fan. This allowed a stainless steel cotter pin to be placed through the hole in the plastic fan and motor shaft. The small red dots on the top of the shaft were to help me with alignment.

    k75s rad fan secured to motor shaft-1.jpg
    That'll fix it for sure. Excellent!
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  4. #19
    I was able to successfully repair the radiator on my 92 K75S. I will describe the things that I did (some worked, some did not). I did not start this repair until I received the used radiator from ebay; the used radiator was to be my back up in the event of catastrophic failure.

    The repair needed to have two main attributes. One seal the leak and two be strong enough to last as a permanent fix. I thought that the aluminum brazing method might work best, but as described above, I initially melted the aluminum can and made a leaky patch. More practice was needed.

    I went back to the aluminum can as my test platform. I punched a small hole in the can approximately the size of the hole in the radiator. Then, using a dremel with wire brush, cleaned the area about the hole.

    can-test1.jpg

    Rather than use the hotter MAAP gas torch, I decided to use a propane torch with a less hot flame. Again, I melted the aluminum can -

    can-test2.jpg

    I continued practicing on the aluminum can and tried to be more careful in heating the can. Eventually I was able to glop some of the lo-melt-temp alloy onto the can -

    can-test3.jpg

    More practice and I was able to get a better appearing patch over a hole without melting the can. These latest patches were securely attached to the can, I couldn't pry them off. -

    can-test4.jpg

    These patches were tested by filling the aluminum can with water and checking for leaks. No leaks with my better looking patches.

    So I cleaned the area on the backside of the radiator using the dremel with wire brush and used the aluminum brazing rods with the propane torch. The patch still looked a bit "gooped" onto the holes in the radiator. And when cool, the aluminum patch could easily be flicked off with a screwdriver. I expect that I didn't heat the aluminum radiator sufficiently with the torch. I was too concerned about melting the aluminum radiator.

    rad-fix1.jpg

    I went back to the Stik-Tite epoxy. I called the manufacturer and asked about success in repairing aluminum radiators. The customer rep. indicated that Stik-Tite was widely used by radiator repair shops and was used to make quick repairs to race car radiators. I used a butane pencil torch to heat the area around the radiator holes and applied some Stik-Tite. This stuff is very easy to work with. -

    rad-fix2.jpg

    I believed that I created a patch that would seal the leak, but I was concerned about the long-term strength of the patch. I decided to make a hybrid patch.

    I took a hot air gun and heated the Stik-Tite until it started to melt. I used a bit of wire to push the Stik-Tite material into the holes in the radiator. Some needle nose pliers were used to remove some of the fins from the core about the holes. I wanted to create a larger surface area for the patch material. The dremel and wire brush was used to clean the exterior area around the holes. I mixed up some JB Weld and dabbed some about the holes. A small strip of aluminum was cut from the can and formed into a "V-shape" and placed (like a tent) over the holes into the soft JB Weld material. I then placed more JB Weld over the aluminum tent and about the cleaned area.

    In making repairs on other bikes I have found the JB Weld epoxy and aluminum "sandwich" to make a pretty strong patch.

    rad-fix3.jpg

    The patch was allowed to cure for 24 hours. I inverted the patched radiator and used the hot air gun to blow hot air upwards into the patch. The idea is to re-melt the Stik-Tite in the hole to more fully seal the hole. When cool the radiator and fan were installed on the bike and all hoses re-connected. Distilled water was placed in the radiator and the system was pressure tested. At 20 psi there were no leaks and the system held the pressure for my hour long test. The water was drained and replaced with a 50/50 mixture of anti-freeze and distilled water. I used the same silicate-free anti-freeze as before.

    The bike was started and allowed to run for a while. I let the bike run until the radiator fan cycled on and off a few times. I took a little ride and observed no leaks. Thus, I am declaring the leak to be fixed.

    I was able to re-use all of the radiator hoses except for the over-flow hose. Fortunately, a replacement was available for about $3 at the local auto parts place -

    rad-ovfl-hose.jpg

    I will make a further suggestion to anyone removing their radiator, either for repair or to make a prophylatic fix to the fan blade (see above).

    Take some time to examine the many wire connections that live in the area below the fuel tank behind the radiator. I pulled each connection apart and used some WD-40 to clean the connectors and then placed di-electric grease about the pins before securely re-connecting things.

  5. #20
    Registered User
    Join Date
    May 2008
    Location
    Western Massachusetts
    Posts
    358
    Thanks for the great documentation on your repair project.

    Your brazing jobs mimic most of my soldering attempts.

    I too have had luck using J B Weld.

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