spark plugs

greasemonkey62 · Post by **greasemonkey62** » Mon May 09, 2011 12:36 pm

I have converted my Model 31 AJS 62/63 Model 31 to 12 volts and also fitted an inductive discharge unit (this replaces the condenser and prevents points pitting), using all Boyers parts, I am still using the original advised spart plug gaps of .20 to .22 and wondered if the later 12 volt models had a different spark plug gap, if someone has the 12 volt version manual does it state a different spark plug gap for 12 volt systems??
The bike runs well but I wondered if it would need a different gap now.

Cheers Ray.

Rob Harknett · Post by **Rob Harknett** » Mon May 09, 2011 1:54 pm

Would not had thought the spark plug gap would be any different.
Blubs would need changing, usualy thing people forget when changing from 6v to 12v
is the 6volt horn to 12 volt horn

Rob Harknett · Post by **Rob Harknett** » Mon May 09, 2011 1:57 pm

PS Additional thing I also fitted was a rectiferer with a big finned heat sink fron JSL plus the 12 V horn

petert120r · Post by **petert120r** » Mon May 09, 2011 4:41 pm

A 6v horn will work fine on 12v provided you don't lean on it constantly like a Cairo taxi driver

greasemonkey62 · Post by **greasemonkey62** » Mon May 09, 2011 4:45 pm

I have already changed the bulbs including fitting an LED rear light cluster inside the original light unit from Goffs which is excellent, I left the horn as it was, it works at a higher pitch but thats no problem, I just wondered about the spark plug gap.

greasemonkey62 · Post by **greasemonkey62** » Mon May 09, 2011 4:52 pm

quote:
PS Additional thing I also fitted was a rectiferer with a big finned heat sink fron JSL plus the 12 V horn
The rectifier is no longer needed with the Boyers system, cheers Ray.

Groily · Post by **Groily** » Mon May 09, 2011 6:51 pm

Not to confuse the BB ignition unit with the typical BB Power Box combined rectifier/regulator . . . same brand name, different bits of kit.
A JSL rectifier will do fine in a standard system, as would one or other of the nice Mr Goff's combined regulator+rectifier boxes, which are very fairly priced I think. But somewhere somehow from somewhere you do need a rectifier if you've got an alternator!
For my money, the combined reg/rect boxes beat hands down a stand-alone rectifier + either zener diode or the older switchgear that sort-of controlled the charging side, any night!

greasemonkey62 · Post by **greasemonkey62** » Tue May 10, 2011 12:29 am

no it is just a single phase Boyers control box and an inductive discharge unit that replaces the condenser no rectifier at all needed with the Boyers system.

Groily · Post by **Groily** » Tue May 10, 2011 1:00 am

Think you'll find there's a full wave bridge rectifier inside the Boyer control box you mention Ray, which is one of several available types of combined rectifier and regulator for single phase alternator systems. But yes indeed, no need for a traditional Lucas-style rectifier, 'tis happily very true.

greasemonkey62 · Post by **greasemonkey62** » Mon May 16, 2011 9:00 pm

also Boyers had said as the electrics are now more powerful after the 12 volt conversion that the spark plug gap can now be 28 to 30 thou instead of the six volt setting of 20 to 22 thou,
I opened the plug gaps up to 28 thou and it has a much much better spark now.