questions about ignition system

L.A.B. said:
Probably none but the timing holes are normally positioned at the bottom left.
Click to expand...
I've never even considered the position of the holes, I just orient it to make the wiring have the least stress. I've had my share of wire failures at or near the stator.
 
I would replace that 12v coil with a 6v before going too far. Your total coil primary resistance is about 3.2+1.6=4.8 ohms which is getting close to the edge - not sure on Boyer but most EIs expect 3.0 to 5.0 ohms and the coils must be the same to provide the same spark to both sides.
 
marshg246 said:
I would replace that 12v coil with a 6v before going too far. Your total coil primary resistance is about 3.2+1.6=4.8 ohms which is getting close to the edge - not sure on Boyer but most EIs expect 3.0 to 5.0 ohms and the coils must be the same to provide the same spark to both sides.
Click to expand...
thank you
 
marshg246 said:
not sure on Boyer but most EIs expect 3.0 to 5.0 ohms
Click to expand...
3) The maximum ignition coil current through the unit must not exceed 5 amps.
The total ignition coil resistance should not be lower than 3.5 Ohms.
4) For low compression engines two 12 volt coils (4 Ohm) in series are satisfactory,
for racing and high compression engines two 6 volt coils (2 Ohm) in series, or one 12
volt 3.5 ohm or more primary winding resistance dual output coil will give the best
results.
 
A bit of disciplined thinking might be appropriate. How can it possibly be correct with two different voltage coils fitted ? Is it supposed to feel better as you ride around left-hand corners ? The weights of the coils might be different. If it has a Boyer, wasted spark is the usual. I just use a double ended 12 volt coil from a 4 cylinder Honda. When a motorcycle is tuned, the ignition system is the critical component - it must be reliable.
 
If you are getting spark try draining the crankcase sump. Nortons are notorious for wet sumping.

Too much oil in the sump makes the bike very hard to start.

If you don’t already have one, buy a service / workshop manual.
 
mauricedonini said:
Plugs - the motorcycle came with NGK BP7ES. It now has NGK BPR7ES. There are two different spark plug caps/wires. One is Beldin. One - Lucas. Markings are feint.

The carb was cleaned because the two times I was able to start the bike, it would run on choke/enrichener but die with the choke/enrichener off.

I did pull the plugs out and kick the motorcycle over. Spark was their on both plugs but not very strong. Also only seems to spark during the last quarter of the kick.
Click to expand...
BPR7ES are resister type plugs (that's what the R stands for)
I believe you will need non resister plug caps with these type plugs
And the pair of 6v coils will be a good move for the Boyer ignition
 
The comments above have been helpful - thank you.

Here's an update;

It was discovered that the coils and the spark plug wires were different. New 6 volt coils and spark plug wires have been order. Consistency doesn't hurt. Also, reinstalled the old plugs (BP7ES).

Took the advice above and put a teaspoon of gas into the cylinders and the motorcycle did start up. Subsequent starts, without gas in the cylinder, were successful.

Will try again tomorrow when the motorcycle is stone cold.

Thanks for all the help.
 
If you're going back to the non-resistor plugs (BP7ES), then you should use resistor caps. That old Boyer might misbehave without them.
 
acotrel said:
A bit of disciplined thinking might be appropriate. How can it possibly be correct with two different voltage coils fitted ? Is it supposed to feel better as you ride around left-hand corners ? The weights the coils might be different. If it has a Boyer, wasted spark is the usual. I just use a double ended 12 volt coil from a 4 cylinder Honda. When a motorcycle is tuned, the ignition system is the critical component - it must be reliable.
Click to expand...
I like your reasoning , however I also like polished coils.
 
Yakatak said:
If you're going back to the non-resistor plugs (BP7ES), then you should use resistor caps. That old Boyer might misbehave without them.
Click to expand...
Boyer MkIII and MkIV do not require suppressed caps/plugs/leads.
"Why Do I Need To Use Suppressed Plug Caps?
MKIII and MKIV do not require suppressed plug caps for operation although we recommend using supressed 5000 ohm plug caps. Micro Digital and Micro Power units must be fitted with supressed plug caps. Plug caps fitted with suppression resistors are usually fitted to prevent radio interference. Radio interference (noise) can cause more complex electronic circuits like radios and computers to malfunction."
johnm said:
Try contacting Boyer to get an instruction sheet. With the mixing of coils etc I'd recomend going through the whole installation to see what other little mysteries might be found.
Click to expand...
I had already posted the link to what is probably the relevant instruction sheet as the MkIV sheet can be used for the MkIII.
 


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