Britbike forum Forums British motorcycles in general The triple forum Difference between boyer mk4 triple and twin ignti

Trying to trouble shoot why a 74 T150 won't start. It backfires and pops but won't run. With fully charged battery 13 volts, when connected with a voltmeter to the white feed and ground it only measures 11.1 volts. Box was drawing over 3 amps. Boyer said this is to be expected with 3 four volt coils in series and the triple box.
However, doing the same test with a Norton Commando was only drawing 0.2 amps. Boyer said this was normal for the twin box as it only sees full current for a second or two.
I seem to recall that the Boyer Box on twins doesn't turn itself on until the crank rotates to save the battery from running down. Does the triple box not have this feature?

Hi,

https://www.triumphrat.net/threads/...wins-and-triples.995962/#post-2004318213

The T150's primary problem is the 2V drop - to maximum 11V - between battery -ve and the Boyer-Bransden Box White wire connection. It's a 12V electrical component, the three coils connected in series total 12V; 12V is a minimum, not an optional extra.

The Box on the T150 is a Mk.4. Its electronics draw barely anything (@NickL says ~250mA), it's the connected coils that draw the Amps, 3A~4A total is perfectly normal for any coils connected to any 'MicroMark' or MicroDigital or similar e.i.

Otoh, your Norton Commando e.i. is a MicroPower or similar Pazon. Works completely differently from any 'MicroMark', MicroDigital or clone. Comparison is irrelevant.

No. Thankfully.

Hth.

Regards,