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  1. #29
    Join Date
    Aug 2013
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    1 mile east of the Rocky Mountains.
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    872

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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.

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