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April 26, 2017, 12:31:52 PM
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  Bolt size for bearing cup on 1970 Oly drive axle
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Bolt size for bearing cup on 1970 Oly drive axle
« on: March 25, 2017, 03:26:36 PM »
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I'm  building up a 1970 Oly.  The tunnel came to me without a track so I don't have original bolts for the mag side bearing cup on the drive axle. I've tried a 1/4 x20 coarse thread, 1/4x28 fine thread and even a M6x1.0.  All are resisting.  I'm sure it has to be a 1/4 but not sure if its coarse or fine thread. I'm reluctant to "bully " a bolt in there with force or even clean it out with a tap as I don't want to wreck one of the welded in nuts and create yet another project.  But if I knew for sure what size it is supposed to be I will have at it with appropriate bolt or tap if need be.  Anyone know? Or know where I could look this up?
Thanks in advance
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Re:Bolt size for bearing cup on 1970 Oly drive axle
« Reply #1 on: March 25, 2017, 06:54:41 PM »
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Boy, what were those guys in Quebec thinking all those years ago? I'd have thought the sled would be all imperial except the rotax parts.  Interestingly, the m6.0 was the only one that turned into the hole but it wouldn't snug up. So your thoughts on m6.5 seem spot on. 
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Re:Bolt size for bearing cup on 1970 Oly drive axle
« Reply #2 on: March 26, 2017, 06:44:38 AM »
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I am very certain it is a 1/4 - fine thread bolt for the bearing cup. I will try to confirm this later on today when I get to the shop.
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Re:Bolt size for bearing cup on 1970 Oly drive axle
« Reply #3 on: March 26, 2017, 08:14:17 AM »
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Quote from: Doonut on March 26, 2017, 06:44:38 AM   

I am very certain it is a 1/4 - fine thread bolt for the bearing cup. I will try to confirm this later on today when I get to the shop.


Like Darren says, 7/16" head hex 1/4-28 fine was oem. Someone may have forced a 1/4-20 or metric at one point, and messed up the thread. Ski Doo made a separate "ring" that you could purchase and use if the threads got stripped out, and it was 1/4-20 coarse. Only metric components on pre 1980's were anything that bolted to the engine.
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Re:Bolt size for bearing cup on 1970 Oly drive axle
« Reply #4 on: March 27, 2017, 04:30:10 AM »
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Thanks for the info guys.  On this info I went ahead with the 1/4x28 thread and 2 of 3 cleaned out and worked perfect. The last one was cleaned with a tap but still won't snug up. It tightens to a point then spins loose, then tightens to a point, then loosens....  If no other idea hits me I may thread a longer bolt through and spin a nut into the inside. (Pity the person in the future who finds 2 bolts pull out but the third one doesn't....)
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Re:Bolt size for bearing cup on 1970 Oly drive axle
« Reply #5 on: April 11, 2017, 03:15:54 PM »
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All they are is a nut that is spot welded inside.  You could grind off what ever is inside and spot another one on, or just put a nut on it.  Easy enough to reach.  This way you wont have a bolt sticking out much farther inside the track area.
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