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?

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.

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.

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

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.

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

Thanks, do you know how wide the standard thrust is?

Standard thrust is 22mm

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