Boyer Install advice

Hi All, I do not have the bike in my possession for another couple weeks. Just want to premise it with that so people know I am working only from pictures and instruction manuals. I like to understand what I am getting into before i take possession so I have as little downtime as possible. I have a very short riding season, and waiting for parts, etc. takes up a huge portion.

Having said that, i bought a 72 that has a boyer installed. As soon as I get the bike I like to check ignition, compression and carb before even attempting to start. The bike was not a hack job and seems to have been put together properly, but alas, I am not buying it running. I have installed a few electronic ignitions on a few different bikes over the years.

I am looking at the boyer install instructions for the commando, as I will be using them to make sure everything is correct when I go to check it over. The one item in the instructions seems very confusing to me:

"5) Set engine at 31 B.T.D.C. on the alternator mark (ensure correct mark is used - there are two marks on the alternator on 1972/3 models, use the mark indicating T.D.C. with the pistons in top position)."

This point from the instructions is saying "set it to 31 BTDC by putting the piston at TDC." It makes no sense and is must not have been written properly. I was wondering if someone can tell me what it is supposed to mean? Am i setting it 31 or not?

It's telling you to set the crank to 31 degrees before TDC by using the correct one of the two marks the rotor has. But to determine which of those two marks to use, set the engine at TDC (us a straw or chopstick down the plug hole and feel the piston) and notice which mark is at Zero (put a paint pen mark on it if you like). Then rotate the engine back to 31 BTDC and static set the Boyer as per the instructions. The other mark is 180 crank degrees out, which is 90 cam degrees, and if you mistakenly use this mark you'll be 90 degrees out on your Boyer timing.

Holmeslice said:

and notice which mark is at Zero (put a paint pen mark on it if you like).

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There is no zero mark so you just have to turn the crank backwards from TDC (measured down the plug hole) to 31 degrees BTDC on the timing scale.

L.A.B. said:

There is no zero mark so you just have to turn the crank backwards from TDC (measured down the plug hole) to 31 degrees BTDC on the timing scale.

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Good one, Les. I suppose I work with degree wheels more often than the marks in the primary cover.

Holmeslice said:

I suppose I work with degree wheels more often than the marks in the primary cover.

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Yes it is a good idea to check the accuracy of the degree scale with a degree wheel.

Holmeslice said:

It's telling you to set the crank to 31 degrees before TDC by using the correct one of the two marks the rotor has. But to determine which of those two marks to use, set the engine at TDC (us a straw or chopstick down the plug hole and feel the piston) and notice which mark is at Zero (put a paint pen mark on it if you like). Then rotate the engine back to 31 BTDC and static set the Boyer as per the instructions. The other mark is 180 crank degrees out, which is 90 cam degrees, and if you mistakenly use this mark you'll be 90 degrees out on your Boyer timing.

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Okay, i understand. It's a bit tough working purely through visualization. But if I understand you correctly, I'll find actual TDC by using a chopstick (or whatever in the barrel, through the sparkplug hole), then I will look through the timing window and, theoretically, one of the marks on the rotor should be within this red circle (see pic)? And after i find the correct mark, and then rotate it back to 31 degree mark. I have read that these marking are not 100% accurate, but will use them at least initially.
Apologies for link, don't think i have ability to upload images.

sonnyjim said:

theoretically, one of the marks on the rotor should be within this red circle (see pic)?

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There's no picture (as I'm in the UK I can't see imgur), so I don't know what you mean by a red circle.

L.A.B. said:

There's no picture (as I'm in the UK I can't see imgur), so I don't know what you mean by a red circle.

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Essentially, it is a picture of the timing plate within the inspection hole (left side stator cover). The timing plate has marks from 18 degrees to 42 degrees, left to right right. I went about a cm from the 18 degree mark to and put a circle around where 0 degrees would be. So i am saying, should the rotor mark to work with be where the 0 degree mark WOULD be. I don't see an actual 8 on the timing plate.

this is the picture i am using, post 6: https://www.accessnorton.com/NortonCommando/tdc-markings.16553/

Correct there's no actual TDC mark so you set the correct rotor mark to 31 BTDC on the scale then check the Boyer rotor position. There's no need to worry about TDC.

Of course the easiest way is to start the engine and check it with a strobe as you should do anyway.

sonnyjim said:

Essentially, it is a picture of the timing plate within the inspection hole (left side stator cover). The timing plate has marks from 18 degrees to 42 degrees, left to right right. I went about a cm from the 18 degree mark to and put a circle around where 0 degrees would be. So i am saying, should the rotor mark to work with be where the 0 degree mark WOULD be. I don't see an actual 8 on the timing plate.

this is the picture i am using, post 6: https://www.accessnorton.com/NortonCommando/tdc-markings.16553/

Click to expand...

L.A.B. said:

Correct there's no actual TDC mark so you set the correct rotor mark to 31 BTDC on the scale then check the Boyer rotor position. There's no need to worry about TDC.

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Correct. Boyer's instructions to use "tdc" is merely a general to verify you're using the proper timing mark.

If you put your finger over the spark plug hole and rotate the rear wheel while the bike is in gear you'll feel it come up compression as the piston rises. And when you do, look at the primary degree scale as you turn the engine and the mark on the rotor will appear. Then you will know you're using the correct mark. Set it to 31, then set your Boyer for its static position, and you should be close enough to strobe.

We're all saying the same thing. Just trying to make the process easier to understand. And after a few more posts it'll be clear as mud!!