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Dave

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Mk3 bigend

Started by yosemite, 27 Oct 2023 at 16:43

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yosemite

 hi my Mk 3 overheated the other week, finally managed to have a look to see the cause, took right hand barrel off to find the big end is siezed so will be looking to have crank rebuilt soon, can anyone recommend somewhere to send it to for a rebuild.
I have a couple that came with the mark1,but both need rebuilt (play on big ends) looking at the parts list all the mark series cranks are the same, is this correct?
Thanks
Paul

Imperial Spanner

Hi, mine is currently being done by Alpha Bearings in Dudley. They're familiar with the Douglas bottom end.  New pins, standard rollers but oversized outer race as conrods were oval and required machining (apparently that's common).  Mike.

yosemite

 Thanks Mike ,  had thought about alpha wasn't sure if they were still in business as had tried to contact them a couple of years back about  a BSA bottom end but never got an answer, just found Eddies pdf on rebuilding bottom ends, using needle rollers, although not had a good look at it yet, just a quick peruse, looks to be a fairly simple solution for a decent machine shop, unfortunately the one I would have used is no longer taking one off jobs.
Had another look at engine starting to suspect that the roller cage has collapsed allowing the rollers to jam the bearing locking the bottom end, rather than the rollers failing as there was none of the usual big end failure rattle, although to be honest what has happened is rather immaterial as the crank will need to be repaired either way.
Paul