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M20/21 - B31/33 Bottom ends?

Hi...

Can someone just confirm that the bearings, end float etc etc are the same, other than the extra bearing in the WDM20 and flywheel weights.

I have just acquired a 1953 B33 which is in need of new bearings... I've never done this job before and am wondering if I should have a go at it. Is it that easy? Anything I should watch out for?

Cheers!
LJ.

Re: M20/21 - B31/33 Bottom ends?

Hi LJ, Whilst there are dimensional differences between the crankshafts, cases etc. etc . when comparing M and B series engines they both use the same main bearings (but 3 instead of 4 in the B series) and the same main bearing spacer. Rebuild procedures are broadly the same and both engine types also share identical timing gear, oilpump etc.....Ian

email (option): julie@wright52.plus.com

Re: M20/21 - B31/33 Bottom ends?

Thanks Ian... I guess the only way is to dive in and find out for myself. It's been a real learning curve just reading back through all the previous posts. Cheers! LJ.

Re: M20/21 - B31/33 Bottom ends?

Hi LJ...It's not really a difficult job to replace the main bearings. Key points are that the main bearing spacer on the drive side is within tolerance and that the oilpump turns freely by hand both before and after it is fitted to the cases. After replacement of the bearings and any fixed fittings the pump and drive are the first things I refit to the cases as a matter of course, as it is then easy to access the driven end of the shaft to test for free rotation. Also remember to replace the mag straps before bolting the cases back together...an easily forgotten detail!.
Removing the main bearing retaining clip can be a real fiddle and it is worth picking up a modern replacement that has 'eyes' on the end to ease replacement....Ian

email (option): julie@wright52.plus.com

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