Author Topic: Main Bearings  (Read 795 times)

Online Russ

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Main Bearings
« on: 05.09. 2013 03:03 »
I am in the process of finding parts for my future engine rebuild and have queries RE the main bearing / bush.  Firstly, what new / modern bearing do I use to replace the original Drive side bearing?
Secondly, my Timing side Bush is 22 thou undersize.  I see on Ebay that 20 thou undersize is available. This will give me 2 thou play but I am guessing this to be too much. Do I need to get a standard bush and have it machined to suit?  Draganfly refer to this bush as a Bearing. Is this simply a difference in description or is it actually replaced with a new / modern bearing?

1951 A10 Plunger.

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
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Re: Main Bearings
« Reply #1 on: 05.09. 2013 07:22 »
Re the plain bush, best thing to do is get the minimum ground off the crank to make it round then get a one off bush made to suit the crank, line reamed in situ to final size, preferably. Lots of info on this forum on that job.

You might be able to make the one off bush from a std bush but the chances are the case housing will be oversize, so you need a one off bush for that reason anyway.

Re the roller bearing, the usual suspects supply those eg draganfly I dont think you will find much lower prices buying from bearing suppliers like skf , toyo etc but you never know, its important to get the version of the bearing that allows for the slight shrink caused by pressing the outer into the case referred to as something like "c class fit" or similar, eg you dot want the tightest clearance version of the bearing.
New Zealand

1956 A10 Golden Flash  (1st finished project)
1949 B31 rigid “400cc”  (2nd finished project)
1968 B44 Victor Special (3rd finished project)
2001 GL1800 Goldwing, well, the wife likes it
2007 KTM 950 Adventure, cos it’s 100% nuts

Online orabanda

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Re: Main Bearings
« Reply #2 on: 05.09. 2013 08:58 »
I like the drive side roller bearing to have a plastic retaining cage (for the rollers), rather than a steel cage. I have been able to buy this version from SRM and Lyford Classic Services, but others may be able to supply this type as well.

The reason is that it is easy (straight-forward) to remove the rollers from the cage (they just push out), so that a split puller can be located against the upper lip of the inner race, and the race removed without damage, if the shimming (for crankshaft end float) has to be adjusted.

The bearing is then easily re-assembled (rollers just push back into the retainer).