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Author: Subject:  Main bearing sizes - help
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question.gif posted on September 1st, 2012 at 10:53 AM
Main bearing sizes - help


I found a type 1 engine in pieces in a mates farm shed. Theres a few bits missing but putting it back together will fill some hours. Number 2 main bearing is missing. The crankshaft sizes of 1 and 3 are 54.68 and 54.60, and number 4 is 39.65. The case bore is 65.52 and 65.48 for 1 and 3 and 50.46 for 4. When buying new bearings what combination of undersize and oversize do I require?
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posted on September 1st, 2012 at 11:30 AM



Looks like your measuring with a vernier so are around about numbers (otherwise you will have problems) You also have to consider the thrust surface of the case where #1 main bearing sits. Sometimes this has been cut to freshen the surface so an oversize thrust might be required. So far you need +0.5 back, -0.5shaft.



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posted on September 1st, 2012 at 11:53 AM



Thanks very much for the advice, yep, a vernier is as good as I've got. Is there a tell-tale that would indicate that the trust has been machined, or a size I should be comparing to.
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posted on September 1st, 2012 at 01:19 PM



Measure the width'thickness of the web of the case that locates the bearing. Often the bearings are custom machined in this area to suit the case. Take a close up pic of the case and/or measure between the shoulders of the thrust(# one) bearing. There are two sizes of thrust available in the .50/.50 main brg kit



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posted on September 1st, 2012 at 10:30 PM



Thanks again, you guys are very helpful, will try and figure it all out and come upwith a solution. I guess at the end of the day i'll enjoy putting it all together again. Cheers.
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posted on September 2nd, 2012 at 11:20 PM



Depending on who reconned the case then there are those that just take 0.5mm off the case and those that take only what is necessary to give a true surface.

Either way, unless your case has been machined by 1 or 2mm then you'll have to get the bearing machined to fit the case. Cost me $50 to have that done and was a nice snug fit :)




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posted on September 4th, 2012 at 08:51 PM



Thanks, do you know how wide the standard thrust is?
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posted on September 4th, 2012 at 09:33 PM



Standard thrust is 22mm



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posted on September 4th, 2012 at 10:44 PM



I'm all over it this weekend, any probs and I'm back here Monday. Thanks for all your help.


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