Boyer crankshaft mounted

Disregarding the fact the setup wont fit inside the outer primary cover, what are the reasons why a Boyer MK3 ignition with one coil and magnet removed couldnt be utilized as crankshaft mounted ignition?

Isn’t this what Steve Maney already offers? Towards the bottom of this page:

http://www.stevemaney.com/products.html

yes, I can see he has done some modifying of the Boyer parts which is not an issue for me.
Modifying the Boyer parts, enlarging the stator plate hole and reconnecting the connections on the back
Making mounting hardware for the rotor and stator
No doubt modifying the primary cover

Hi I had this set up on my racebike. Steve claimed the timing was better off the crank rather than the camshaft.
The bike was not as rough as it is with the Interspan off the cam that I now use. I dont run a full fairing & I worried that if the bike was dropped the whole system would be wiped out & maybe damage the crankcases. The Boyer pick up is neat & was mounted inside the belt pulley. The plate holding the boyer with single pick up is mounted on 3 scews with spacers directly into the crankcases.

Chris

My idea is to use it with existing Lucas alternator, hence modifying (extending) the primary cover hump. no issues there.
Its only for a one off project,

i run a similar crank mounted ignition system (batteryless) on my race bike and although I have a very modified inner and outer primary covers, it still fits inside the outer cover and there fore protected.
I had a low side crash on the LHS last December and no damage as the bike took most of the fall on the clip on nad footrest.
Yes the timing is more accurate directly off the crank.
Regards Mike

Can't see any problems with your idea,I used to have a t500 Suzuki with a Boyer fitted,
This was a permanent magnet alternator similar to Lucas it worked really well

To get more space without raising the primary you can do three mods, each is independent of the other so one alone or combination of 2 may do it.

1. Use the thinnest alternator/rotor combination, this is a 10.5A three phase alternator stator from LAP and a Tiger Cub rotor (will post number later as there are full sized ones used to), shorten the spacers to move the stator closer to the engine sprocket.

2. Fit a duplex primary chain from Andy the Chainman and grind the unused 3rd row of teeth off, has to be ground as even carbide will not touch it. Then shorten the various bits and pieces to allow the alternator to be moved closer to the engine sprocket.

3. Take the degree scale off the outer cover, mill the 2 mounting stubs lower, flatten the scale and drill holes in the cover to match the new scale hole positions (they will be wider apart), tap for 3mm screws and then screw on the scale.

I have done for 3 for a different project so can post pics if needed.

Your ignition advance curve will be significantly diminished due to the relatively greater velocity of the trigger magnet for a given rpm. The magnet is rotating at twice the rpm of the cam shaft and depending upon how it is configured, likely traveling at a greater circumference.

Certainly not a reason not to go with a crank mounted trigger but worth noting.

Dances with Shrapnel said:

Your ignition advance curve will be significantly diminished due to the relatively greater velocity of the trigger magnet for a given rpm. The magnet is rotating at twice the rpm of the cam shaft and depending upon how it is configured, likely traveling at a greater circumference.

Certainly not a reason not to go with a crank mounted trigger but worth noting.

Click to expand...

Interesting Dances, certainly something to think about.

kommando said:

To get more space without raising the primary you can do three mods, each is independent of the other so one alone or combination of 2 may do it.

1. Use the thinnest alternator/rotor combination, this is a 10.5A three phase alternator stator from LAP and a Tiger Cub rotor (will post number later as there are full sized ones used to), shorten the spacers to move the stator closer to the engine sprocket.

2. Fit a duplex primary chain from Andy the Chainman and grind the unused 3rd row of teeth off, has to be ground as even carbide will not touch it. Then shorten the various bits and pieces to allow the alternator to be moved closer to the engine sprocket.

3. Take the degree scale off the outer cover, mill the 2 mounting stubs lower, flatten the scale and drill holes in the cover to match the new scale hole positions (they will be wider apart), tap for 3mm screws and then screw on the scale.

I have done for 3 for a different project so can post pics if needed.

Click to expand...

I'm not at all concerned about fitment or making room so it fits inside the primary cover. My concerns are more about setting the electrical side up.

madass140 said:

Interesting Dances, certainly something to think about.

Click to expand...

If mounted on the crankshaft (at crankshaft speed) it will fire TWICE as often thus wear the spark plugs out twice as quick!

hmm, thanks Bernhard.....

Bernhard said:

If mounted on the crankshaft (at crankshaft speed) it will fire TWICE as often thus wear the spark plugs out twice as quick!

Click to expand...

No, the Maney one has only one magnet and one pickup so it fires every 360 degrees of the crank. The camshaft mounted one has two pickups and two magnets so it fires every 180 degrees of the camshaft ( equivalent to 360 at the crank.

I have used a Steve Maney crankshaft pickup, with his modified Boyer ignition box. The timing curve is different because it is set for full engine speed, not half engine speed. When the belt pully failed and wiped the pickup magnet off the crank spacer I used a twin coil plate in the timing cover, with the same modified box.

Well it worked, except of course it had reduced advance/retard.

I could not use the standard alignment process described by Boyer, as it seems to me I could only get 14 degrees or so of advance from the standard setting.

Not too bad for me since I was using roller starters because it is a race bike. And I know from previous experience you can run fixed ignition at fully advanced when you don't have to kickstart it. My ex work Lucas Rita had no advance, it was jumpered out.

Eventually I changed the Maney Boyer to a Pazon timing cover/cam driven system.....

You can readily see that the crank pick up gives a more stable spark, even with a strobe light, simply because you don't have timing chain lash to contend with. With Maney's set up the circumference Dances mentions is the same! And the magnet does wiz past twice as fast, but I don't see that as detrimental.

The main reason I didn't go back to the crank mount system is that I would have to re engineer several parts, particularly to get them inside a tighter fitting fairing.

With the resources you have I would probably go for it again. but in that case I would look at a pick up mounted to the crankcase itself with a rotating piece mounted behind the belt pulley, which is what Minnovation do with a programmable Racetech Developments ignition system.

kommando said:

To get more space without raising the primary you can do three mods, each is independent of the other so one alone or combination of 2 may do it.

1. Use the thinnest alternator/rotor combination, this is a 10.5A three phase alternator stator from LAP and a Tiger Cub rotor (will post number later as there are full sized ones used to), shorten the spacers to move the stator closer to the engine sprocket.

2. Fit a duplex primary chain from Andy the Chainman and grind the unused 3rd row of teeth off, has to be ground as even carbide will not touch it. Then shorten the various bits and pieces to allow the alternator to be moved closer to the engine sprocket.

3. Take the degree scale off the outer cover, mill the 2 mounting stubs lower, flatten the scale and drill holes in the cover to match the new scale hole positions (they will be wider apart), tap for 3mm screws and then screw on the scale.

I have done for 3 for a different project so can post pics if needed.

Click to expand...

Hi.
What trigger type are you useing?
Pics are allways welcome.

It was not to put a crank operated ignition trigger but to get room for a sprag unit for a starter. Later on I plan to go crank triggered but using a car flywheel tooth sensor pointing at the engine sprocket feeding into a Secu-3 ECU which has programmable firmware and the Norton engine sprocket teeth number is within its range. I have to find a sensor that will mount on the inner primary and not interfere with the chain, not found one yet. Even if I do as there is no missing tooth and as I also want sequential sparks I need a sensor mounted on the cam to identify which cylinder is at TDC, I have this sorted by using a VW sensor and a steel dish mounted on the cam with 2 slots at 180 degrees apart.

appears my biggest concern would be the advance curve.

Looking at it from first principles two magnets on a cam rotor give wasted spark firing every 360 degrees, stick that on a crank and it will fire every 180 degrees and advance twice as fast as the crank spins at twice the speed of the cam. So dropping one magnet on the crank gets you back to 360 wasted spark and etc advance.

how about this stator plate, its height is 1/4" less than the Boyer and the crankshaft centerline to air gap is 1/4" less also,
which would probably help with the advancing issue ?