Boyer ignition question

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Hey there -

I fully admit to not knowing what I'm doing entirely, and will therefore ask some decidedly stupid questions. But those questions need answers anyway, and perhaps I'll get educated in the process...

In another post, I was discussing a starting issue on a friend's '74 850. It was suggested that I check the ignition timing. Doesn't seem like something that is all that hard to do, but I'm having a heck of a time. FYI -this has a Boyer ignition and the magnets are lined up with the logo.

1) Manual says to get it to TDC by rotating the engine with the kickstarter (slowly) until the piston is at TDC and both inlet and exhaust valves are closed. I do this and it appears to me that the timing mark is way way off. Past the 40 degree mark by 1/4". Shouldn't it be 28 degrees? (I have to do a static timing check, I have no scope).

2) Assuming that I do need to advance the timing, or change the timing - uh (dumb question part) how the heck do I do that? My basic understanding is that I should be at 28 degrees at TDC. If I move the rear tire forward so that the mark lines up, I'm affecting the TDC issue, right - so the timing would still be off.

Sorry - Timing has never been my strong suit and this one is confusing me....
 
rpthoth said:
1) Manual says to get it to TDC by rotating the engine with the kickstarter (slowly) until the piston is at TDC and both inlet and exhaust valves are closed. I do this and it appears to me that the timing mark is way way off. Past the 40 degree mark by 1/4". Shouldn't it be 28 degrees? (I have to do a static timing check, I have no scope).

As you are attempting to set up a Boyer then you need to be using the Boyer instructions. Note that you set a Boyer to 31 degrees BTDC and not 28 degrees. So you should be setting the crankshaft to 31 deg. BTDC not TDC.

Boyer instructions (Micro MkIII & IV) http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf


rpthoth said:
2) Assuming that I do need to advance the timing, or change the timing - uh (dumb question part) how the heck do I do that? My basic understanding is that I should be at 28 degrees at TDC. If I move the rear tire forward so that the mark lines up, I'm affecting the TDC issue, right - so the timing would still be off.

There should be a timing scale behind the alternator inspection plug and a scribed mark on the rotor which you use to set the timing to 31 degrees (Boyer)?
The timing scale should really be checked for absolute accuracy with a degree wheel and a piston stop as it can often be a few degrees out?
 
rpthoth said:
1) Manual says to get it to TDC by rotating the engine with the kickstarter (slowly) until the piston is at TDC and both inlet and exhaust valves are closed. I do this and it appears to me that the timing mark is way way off. Past the 40 degree mark by 1/4".

As you turn the crank towards TDC the timing mark (presumably you mean the alternator rotor mark?) should be moving down the scale to zero (TDC = 0 degrees), not up past 40 degrees?



rpthoth said:
(I have to do a static timing check, I have no scope).

You cannot accurately time a Boyer without a strobe. Static timing is only to get it close enough to be able to start the engine so that it can be accurately set with a strobe so the static timing could be 10 or more degrees out.
 
I appreciate the information. My real question is, once I get the engine to BTDC, if the alternator timing mark is not on 31 degrees, how do I get it there?
 
Get the bike on the center stand and shim it if need be to get the rear wheel off the ground. Now put the bike in fourth gear and use the tire as a lever bar to turn over the motor. Start on the job on the timing side use a plastic bar straw in the spark plug hole to rough out TDC (on compression stroke) than back up the engine till you’re about a 1/2 lower than that. Now switch over to the drive side and look in the window turn the tire as the bike runs to get the line on the pointer. If you go past the mark you must go too far back and come back to the mark while moving the motor in the correct direction. Now put the Boyer plate in the middle of the slot and using a 5/16 fine thread bolt in place of the keeper bolt gently knock it out of the taper. N, S, E, W hammer taps work. Now place the rotor so as to see the screw head though the CCW hole in the Boyer plate. Set the taper with the keeper screw. Than and don't skip this step strobe time the bike just as soon as you can. Under the strobe light when it is revved till it advances no further it should appear to land on 31 degrees.
 
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