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Thread: 1928 JD Motor

  1. #31
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    Aug 2013
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    Quote Originally Posted by whp View Post
    I'm going through the process of repairing cracks right now. I'm stumped on how to remove all the oil from the casting as it is almost a sponge. Maybe vapor degreasing? I've had it in the oven a dozen times and the welds are turning out like chicken poo, also they spur more cracks during the welding (casting is hot). After a few rounds of welding and sanding its getting there. Most aluminum welders are used to fresh oil free castings so this old stuff throws them for a loop.

    Steve, I've heard it's old piston rings that get chewed up and get sucked into the breather gear as the crank case pressure is expelled. The piece of ring gets stuck and BAM! Shes cracked.

    Bummer about your pinion area being cracked...
    Will, i admire your can do/will do ability. i am not a welder, don't have the equipment, but i had conversations with the man who did the prep work and welding on my cases. he removed enough metal from the cracks until he felt he was into "clean metal'" although he ran into impurities during the actual welding repair, he was able to make very solid repairs to both cracks, in fact could not see where the repairs had been made after machine work was finished. i wonder if a hot tank ultrasonic bath could pull out some of the oil ?

    fwiw, this 2011 thread is very comprehensive by Jerry Weiland getting his 25 together for the 2012 Cannonball. page 2 he mentions laser welding for hairline crack repairs, i don't know if laser welding is the answer for Mitchell's cracks at the rotary breather and the loads placed on the case at the pinon shaft area. Those with more knowledge and experience will know. http://www.antiquemotorcycle.org/bbo...annonball-Bike
    Last edited by Steve Swan; 07-07-2017 at 02:22 AM.

  2. #32
    Join Date
    Nov 2015
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    Thanks Steve! Wise or not, I try to do almost everything myself cause eventually all of these old timers that know everything will be gone and I'll have to do it all myself. Hopefully some kids come up to me with wild old motorcycle projects when I'm an old timer and I'll know what to do. I too also have not spent the time welding, especially aluminum. I'm a better machinist and I'm not even a machinist in the true sense of the term. I'm a "half ass enthusiast", or so my tool maker grandfather says. Machinist make money.

    Funny you mention laser welding, that's my next stage of chasing hairline cracks. In hindsight I should of maybe done that first. But as you see below my crack went pretty far. I wanted it to be structurally sound. The laser welding I don't think meshes the material in a large enough spot to fully stabilize a cracked region. The welder said he uses .015" rod so it takes awhile to fill. I started by cutting out all of the old material, turns out this has happened before and the guy didn't fix it. The old weld was kind of junk, although the finishing work was nice. I cut it all out with a hand held grinder so a copper plate could be used on the back side to fill the slot and fuse the two sides together. I didn't take any pictures of the after welding cause it was rough. I'll take some pictures tonight and add them to this of the second round of welding. Cracks kept forming immediately after welding. Even straight through the new weld! Annoying that's for sure. Few more welds and more money but it'll be fine.








  3. #33
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    Nov 2015
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    Here is what I ended up with. It was welded 3 times and I cleaned it up two. There was still a ton of oil leeching out even after the oven bakes. I just kept heating it up with an O2/Acetylene torch (not too long in once place and not too intense) while brushing away the contaminants with a stainless steel brush. I'm going to leave the welds on the outside of the case for strength.

    The final weld (the only one I really needed... went to a different welder) was done a bit differently. Preheated the case, brushed away anything that leeched around the welding area, used a tig to heat the area all around the crack until you could see the material fall into the crack. Then he just dripped new aluminum in until it started to rise again. Don't roll dimes! He melted all the surrounding material and meshed it all in with large pool welds. Lots of debris came out of the welds but you just have to stop and brush, and keep going.

    I have not seen too many welding threads on old J cases so I figure I'd drop my two cents in for you.

    Get those cases split and start cleaning them! Vapor Degrease them if possible.

  4. #34
    Join Date
    Aug 2009
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    rural eastern South Dakota
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    those welds welds appear to be done with wire feed. A tig unit is imperative these days, has made better work of these jobs for decades now. I've seen it done with gas torch but it's not nearly as clean. .. On the pan head heads, we've seen tigs make multiple efforts before succeeding. When you've found a good welder (who hasn't gone blind yet), make good friends with him.

  5. #35
    Join Date
    Aug 2013
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    Mitchell ! if the belly numbers on your 28 motor are not matching, perhaps this could save alot of time and expense...... http://www.ebay.com/itm/OEM-1925-192...tZY7Lx&vxp=mtr

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