Removal of Boyer rotor

Could someone please advise on how to remove the Boyer rotor from the end of the camshaft without damaging it?

Also, my alternator rotor has three marks on it. I thought some rotors had two marks but not three. I have a 1973 850 Mark 1. Which mark is used for ignition timing? Can one find TDC without removing the primary cover?

Dave

With the bolt removed you can use a pair of opposite levers to break the joint (even one will do it) It won't take much effort. put some packing under the levers to protect the aluminum if you're concerned. As for the rotor...three marks? would that be for a triple maybe?
If the engine is running why don't you highlight the marks with different colours? Then you can strobe and determine which is in use. Or find the cylinder with both valves closed and bring the pistons to TDC. That is the correct way!!

Dave,

There are threads in the rotor for it's removal. As far as a rotor with three marks at 120deg, I don't know if one is going to be TDC or not. You could use a thin wooden dowel in the sparkplug hole to let you know if you're coming up to tdc. It would be a fair guess if there's a mark coming by the index in the cover that you do have a workable mark, you may need to use a degree wheel to make your own mark.

Keith and Bob — thanks very much for the tips. I managed to extract the rotor without damage. At first, I didn't notice that there were threads in the rotor centre for its removal.

Thanks, Seeley 920, for that private message about the rocker pin extractor slide hammer.

The reason I asked about the alternator marks is that I wanted to line things up reasonably close so that it will start without a vicious kickback so that I can time it accurately with a strobe. I can line it up now because I marked the stator plate against the timing case and the approximate position of the rotor relative to the stator plate, being careful not to move the crank until the stator and rotor are replaced. I guess when the engine is running, it should then be evident which alternator mark is the right one to use.

Dave

daveh said:

Also, my alternator rotor has three marks on it. I thought some rotors had two marks but not three. I have a 1973 850 Mark 1. Which mark is used for ignition timing? Can one find TDC without removing the primary cover?

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The fact that the alternator rotor has three marks (presumably 120 degrees apart?) could mean it is a rotor from a BSA or Triumph triple, in which case I'm not sure if any of the marks are correct?

Any chance of a photo of that rotor?

Les, the rotor has three marks 10 degrees apart! The middle mark appears to have been scribed alongside the raised part of the mark, and all three have been sprayed with black paint. I am guessing the middle mark is what the previous owner used to time the engine. I've tried taking photos but the primary is still on and it's difficult to get good shots. I have heard of rotors with two marks, in which case, how far apart are they in degrees?

daveh said:

the rotor has three marks 10 degrees apart! The middle mark appears to have been scribed alongside the raised part of the mark, and all three have been sprayed with black paint. I am guessing the middle mark is what the previous owner used to time the engine. I've tried taking photos but the primary is still on and it's difficult to get good shots.

Click to expand...

Ah...yes, that's OK then, the scribed mark in (roughly) the centre of the raised pad will be the one. So don't worry about the photo!


Many rotors have two raised pads, positioned 180 degrees apart, with a scribed line on each, if so, then the second pad and mark can be ignored. http://www.oldbritts.com/image/11_068100b.jpg

Les — thanks, as always, for your excellent technical advice! All I need to do now is line it up approximately and then strobe it to 31 degrees at 5000 rpm.