Author Topic: B40F wrong AAU ? electronivc ignition ?  (Read 298 times)

0 Members and 1 Guest are viewing this topic.

hoogerbooger

  • Royal Star
  • ***
  • Posts: 231
    • View Profile
B40F wrong AAU ? electronivc ignition ?
« on: 08 August, 2021, 11:35:19 »
Just read Rupert Ratio who says AAU should be a 15degree one for a B40 star.  Have just re-found the photo I took for my record confirming I have a 10 degree one. So what difference should this make ?

(it's not running currently. I presume the erratic idle I had that I had failed to solve is un-related to the AAU and I have a new Concentric carb to fit, carb issues being my conclusion).

As a replacement decent 15 degree AAU may be hard to get I am now thinking I may have to go electronic. So anyone got a 6V electronic ignition on their B40F ? that they are happy to recommend or comment on ? 


hoogerbooger

  • Royal Star
  • ***
  • Posts: 231
    • View Profile
Re: B40F wrong AAU ? electronivc ignition ?
« Reply #1 on: 08 August, 2021, 17:24:40 »
Oops. Just found an answer on a previous string I was involved in (!!) Julian S provided the attached indicating The AAU was changed to a 10 degree unit. So mine is correct in spec ....but old

(Still interested to hear about any reliable 6v electronic ignition though).

Have searched for info on replacement springs. 1965 parts book doesn't help. Best I've found is advice on the B50 forum:
http://b50.org/phpBB2/viewtopic.php?p=50671&sid=447ff271a3505e55be48fc5b8ed408b7#p50671

However Rupert Ratio just says the specific type changed several times & where there's a choice fit the strongest ( but also says the correct part is No. 99-1011).

I'm left not being sure how important having the "right" springs are ? or to what degree olds springs may affect function. Any views ? 

Also should the welded tabs on the 4CA AAU perpendicular to the plate ?





« Last Edit: 08 August, 2021, 17:27:54 by hoogerbooger »

DAVE BRADY

  • Golden Flash
  • *****
  • Posts: 1982
    • View Profile
Re: B40F wrong AAU ? electronivc ignition ?
« Reply #2 on: 08 August, 2021, 17:51:49 »
Hi,

As with any springs on an AAU, they are there to return the timing to the retarded position to help starting and to allow a gradual increase in advance so that the spark is in the best place until full advance is needed.
Weak springs will allow the timing to advance too quickly or even just under the rotation caused by kickstarting.
I suppose that if the springs are weak they could be allowing the timing to fluctuate a tickover/low revs. but could be crab. related as well.
I have no specific experience of EI on 6v B40 (mine had points) but 12v on A65s and A10 and EI does offer an improvement in performance and reliability over points. 

Dave.

hoogerbooger

  • Royal Star
  • ***
  • Posts: 231
    • View Profile
Re: B40F wrong AAU ? electronivc ignition ?
« Reply #3 on: 10 August, 2021, 15:52:44 »
( thanks Dave)

I have some replacement springs now. My logic is use these as most likely to be correct and compare with existing ones for the record
(....In situ one of the existing springs looks stretched and the post it's attached to seems to have been bent out... presumably to compensate and remove slack at the stationary position).

(the replacement springs are slightly different lengths. One is 17mm and the other 16.6mm. bought as Lucas part no: 54415640 from Greystone Enterprises who do Triumph Tiger Cub spares))

However looks to me you need to remove the cam from it's spindle to unhook the old springs/attach new. reading seems to say it's a press fit. So sounds like I need to lever the cam carefully off ?? but I can't specifically find anything saying this. Should this be possible without damage ?