Can anyone solve this puzzle? I am trying to start my 72 750 for the first time since a total rebuild,I set the engine to TDC on the compression stroke,both valves closed,then backed it off till the line on the rotor is at 31deg (Boyer ignition), kicking back every time like it was too far advanced so removed primary outer case and fitted a timing degree disc and set that to 31deg,removed disc and refitted the case to check if the mark on the rotor lined up with 31deg on the scale in the inspection hole, miles out,the line on the rotor was off the scale to the left so although I might be able to start it I could not strobe it with the marks this far out. I am not going to attempt to start it now incase I am doing something wrong, I can't work this one out,can anyone see something I am doing wrong? I am beginning to think that dementia is setting in and I am doing something stupid.
The rotor is keyed to the…
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Previously richard_payne w…
Previously richard_payne wrote:
The rotor is keyed to the crank so unless the key is missing or sheared then at 31? BTDC, the rotor mark has to be more or less in the area of the 'window'. The plates can move and be a few degrees out, but not so far that they won't start.
The initial symptoms that you describe could well be due either to a partially discharged battery or having the wires from the pick-up reversed. Both of these are typical Boyer traits and will cause the thing to sit on full advance.
If crank and rotor have not been changed and keyway is intact, the explanation cannot lie with the components. Maybe a miscalculation or something moved ?
If it's a new rotor and the keyway is off, then anything is possible.
Hi, Thanks for replying, I have just checked the rotor again and everything is OK, sitting in the key way as it should, I have also looked at photos of rotors and it is identical with key way and timing marks in the right place so I just don't get why it's not lining up with the scale in the window. I will try both things you mentioned (battery and wires) and see what happens. Thanks.
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One other item to check is…
One other item to check is the hole you are using for the boyer on the stator, there are 2 holes, a clockwise and an anti clockwise one so check you are using the right one to align to the magnet on the boyer rotor.
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Previously john_holmes wro…
Previously john_holmes wrote:
One other item to check is the hole you are using for the boyer on the stator, there are 2 holes, a clockwise and an anti clockwise one so check you are using the right one to align to the magnet on the boyer rotor.
Hi John, I have just gone out and checked that and it's the correct anti clockwise hole I was using, thanks. Billy.
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The rotor is keyed to the crank so unless the key is missing or sheared then at 31? BTDC, the rotor mark has to be more or less in the area of the 'window'. The plates can move and be a few degrees out, but not so far that they won't start.
The initial symptoms that you describe could well be due either to a partially discharged battery or having the wires from the pick-up reversed. Both of these are typical Boyer traits and will cause the thing to sit on full advance.
If crank and rotor have not been changed and keyway is intact, the explanation cannot lie with the components. Maybe a miscalculation or something moved ?
If it's a new rotor and the keyway is off, then anything is possible.