Electronic ignition problems.

bubbles

bubbles

Registered user
Joined
Nov 30, 2006
Messages
443
Reaction score
0
Location
camelford cornwall UK
My 1978 80/7 has had a Boyer Bransden electronic ignition system on it for the past 31 years and 130,000 miles. I have borrowed Pastymans xenon timing light (thanks Tony) to check the timing as Rob Farmer :bow said at the Wee..kend it sounded on tickover like it was a bit out. Anyway whatever I do I can't get it right at tickover and 4500rpm. If I set it correctly for tickover on the S mark in the crank case hole, then at 4500rpm the F mark has not appeared and I can still see the bottom of the S marks if I look from below towards the top of the hole. So at the moment it is set advanced on tickover (800rpm) with the S mark just starting to appear from the top of the crank case hole if the tickover fluctuates below 800rpm, which it tend to do as this makes the tickover a bit lumpy.
So the question is has something happened in the magic box of electronic tricks (transistor box) :confused: that must alter the timing depending on the rpm as the auto advance unit is removed with this system?
Should I get a complete replacement timing system? :nenauhttp://www.motorworks.co.uk/bmw/pro..._15_20_IA_40&header_text=&header_text_image=0 I really don't want to go back to points again.

DSCN4654-1.jpg


DSCN4942.jpg


DSCN4657.jpg
 
I know shag all about airheads, but if this were a car of a similar age I would suggest that either:

  • the ignition advance bob-weights have seized, and/or ...
  • the advance springs have broken

Greg
 
Hi

I had a Boyer Bransden briefly on my R60/6 many years ago and I had exactly the same issue. I contacted Boyer Bransden and the unit was performing exactly as designed. It did not advance the spark as much as the mechanical system.

It is intended that you set the timing to the F point at 4500 revs and accept the greater advance at tickover. Personally I did not like what this did to the feel of the bike (lower torque at low revs). After a month I sold the Boyer Bransden and fitted a points assistance system that used the mechanical advance.

Steve
 
Hi Geoff,

I was going to reply to your PM. Being a bit slack at the minute.

We had exactly the same issues with the analogue unit on RichC's R90/6. Rich bought a Boyer microdigital to replace it and it's made a hell of a difference to the way the bike runs.

I was curious how yours turned out when you posted about setting the ignition. The analogue units clearly do not perform well.
 
Thanks Steve and Rob that explains a lot. So is the Boyer Bransden system now sold by Motoworks (see link in OP) the improved or digital one, cause it looks just the same as the one I have apart from the colour of the transistor box is red and black on the one I have?

I still have the original box mine came in, does this make it collectable :D.

DSCN4647.jpg
 
Thanks also to Greg for trying to answer my question, it's always good to get a response straight back in those dark moments when its all going wrong :(

Even if it is the wrong one :D.
 
The Red one is the Microdigital.

Snowbums site has some info on the early Boyer (Yours) http://bmwmotorcycletech.info/Ignition.htm

Basically says " The early Boyer models also have an ignition curve that does not well match the Airhead engine requirements. In particular, the early Boyer had an ignition curve that was slow rising and kept rising, there was no practical limit....the ignition would continue to advance with increasing RPM. "

Are you going to treat yourself to a Microdigital Geoff? After 30 years of running your old one I think you've had your monies worth :D
 
Rob Farmer said:
Are you going to treat yourself to a Microdigital Geoff? After 30 years of running your old one I think you've had your monies worth :D
Click to expand...

Yes I think I probably will Rob, but it will have to wait till we get back from the Moto Piston Rally as have only just spent a couple of hundred pounds at Motoworks on Tyres and bits. Only 1 full week before we travel now. Taking the old R80 abroad for the first time in its life has certainly focused attention on getting all those little things that needed doing sorted. :thumb2
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.

Similar threads

sj_4x4
R80 points and electronic ignition
Replies
10
Views
963
sj_4x4
sj_4x4
ELIMINATOR
Iridium spark plugs for California 3, 36mm carbs , electronic ignition. Think it;s Di
Replies
8
Views
1,843
Neil W
Neil W
Electronic Ignition
Replies
2
Views
1,184
chasbmw
chasbmw
electronic ignition for r 100rt
Replies
5
Views
1,609
Kenny
Kenny
Electronic Ignition system
2
Replies
34
Views
10,214
chrisshrops


Back
Top Bottom