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General => Douglas Motorcycles - General Discussion => Topic started by: Bynorthsea on 19 Feb 2019 at 17:29

Title: Crankshaft Rebuild
Post by: Bynorthsea on 19 Feb 2019 at 17:29
I have managed to get only two estimates for rebuilding my Dragonfly Crankshaft, Applebee Engineering and Alpha Bearings, looks like  a big investment so has anyone an opinion as to the best or any other companies that you would recommend??
Title: Re: Crankshaft Rebuild
Post by: eddie on 19 Feb 2019 at 18:31
Have a look at the attached file - it summarises the method I used to rebuild my Dragonfly crank. That crank has now done about 30,000 miles and is as good as the day I fitted it. Most of the commercially rebuilt cranks with thin wall liners fitted into the conrods that I have seen, have had seriously short working lives due to the liners being too thin and flexing, resulting in the surface of the liners breaking up. If you go down the route I took, I would suggest it would be a good idea to halve the number of oil holes in each big end journal (to ensure the oil gets divided equally between the 2 big ends) - worn Dragonfly cranks throw most of the oil out of the front big end, and starve the rear.
     Hope some of this helps,
                                            Regards,
                                                          Eddie.
Title: Re: Crankshaft Rebuild
Post by: Bynorthsea on 19 Feb 2019 at 18:47
As always thanks Eddie. I had seen your PDF and would have liked to have gone down that route but I don't have the engineering resources, do you know anyone that is familiar with the process and would take the job on?
Title: Re: Crankshaft Rebuild
Post by: Neville Heath on 21 Feb 2019 at 16:29
If you are prepared to take a chance on a standard crank I have one I would sell. I stripped it some time ago, cleaned it all out, and put the pins back in the centre section. I think it is an Alpha rebuild. Both pins measure 1.274" dia. and are round and true, but one has slight wear where the outside of the roller cage has rubbed. I.E. not the roller track.  Front and back ends are good. Good threads and undamaged flywheel taper. There is however a problem that maybe the connected to the wear referred to on the pin. There is only one useable roller cage. Maybe yours might fit. If you are interested send me an EMail. See page 20 Jan/Feb ConRod.   
Title: Re: Crankshaft Rebuild
Post by: isettaman on 26 Feb 2019 at 22:30
Alpha Bearings did a good job on my 80 plus crankshaft recently - not a full rebuild, though, just a realignment. Chris there is very helpful and friendly.
Dave