57 thuderbird aternator burn out problem

[thunderbird]

hi can anyone help.I rebuilt a 57 thunderbird last year after doing 350 miles the alternator burnt out it was secondhand when fitted, so i replaced it with new rotor and stator, i got about a mile up the road and this one burnt out as well.I stripped it down and the only thing i could see was the rotor was offset within the stator i fitted another new rotor and stator making adjustments to the stator plate to ensure the rotor was runninig central,this alternator has burnt out the same way.The bike is converted to 12v with new wiring loom battery regulator/rectifyer can anyone help Regards Steve

[L.A.B.]

Can you say what type of regulator/rectifier you have?

And could you give a brief description of how the charging circuit is wired?

Can you explain exactly what you mean by "burnt out"? Did they all physically overheat? Or did they all just stop working?

There should be a gap of about 6-8 thou between the stator and rotor all the way round. What were the gaps on yours?

Was there any evidence of the rotor coming into contact with the stator on any of them?

Which alternator (stator) types were fitted, single phase RM21/RM23, three phase RM24 etc.?

Please, try to answer all the above questions, if you can.  

[thunderbird]

hi  thanks for your reply,the power module is single phase 12 v 160 watt rectifyer for lucas 120 watt and alton 150 watt alternators it is wired as per instructions with the two yellow wires conected to the green/black white /green aternator wires,the alternator is a sparks make bought as a replacement for the original lucas unit it is 12v single phase resin encapsulated.When i fitted the last alternator i was very carefull to ensure the rotor and stator were central to each other with correct gap between the two, when they have burnt out the resin on the stator has melted from the inside all the way round the rotor has picked up and started to meltdown loosing its magnetism. I have spoken to triumph twin spares who i bought the alternator off of and they have suggested the main bearings may be worn or the crank may be bent but the engine does sound ok when running is there any way round this other stripping the engine and replacing the mains/checking the crank thanks Steve :-/

[L.A.B.]

I have spoken to triumph twin spares who i bought the alternator off of and they have suggested the main bearings may be worn or the crank may be bent

I think the diagnosis you have been given by TTS could well be correct?
If you remove the stator and pull the end of the crank up and down fairly hard can you feel any play in the D/S bearing?

[thunderbird]

hi L.A.B.  after speaking TTS again i checked the end of the crank with dial gauge and its as straight as a die, i then fitted the rotor and checked with the engine running only very small movement shown ,i then fitted the stator and it was offset slightly  to overcome this i drilled the holes out in the stator to allow for more adjustment i used plastic strips of 8 thou to ensure it was central. thankfully this seems to have done the trick i have done about 20 miles on  the bike and all seems ok  and aternators charging. Thanks for your interest Regards Steve