Electronic ignition

[Jan Buchwald]

Has anyone ever succeeded in putting elektronic ignition on a Scott (with distributor).
Does the electronic unit “know” that the distributor is running at engine speed, or does give the advance too early, or doesn’t it matter.
Look at Brian Marchalls thoughts in the topic about distributor springs.
I think I will contact some of the manufactorers of electronic ignitions and ask them. It might be a winters project, making the ignition electronic. But it came from another four stroke

[Anonymous]

I’ve done lots of CDI’s for two strokes but never got round to putting one on a Scott yet. Using a hall effect trigger and winding your own primary coil then using a normal motorcycle coil from a CDi bike works very well. Here is a simple circuit I developed to run off 6v with a home wound primary coil

If course you get no electronic or mechanical advance, but actually the trigger delay of microseconds provides a built in advance/retard of a few degrees. As I mentioned in the other thread I find spark advance/retard more of an ornament on a Scott anyway.

If you are playing around with CDI just be aware of the primary voltages you can acheive though. With a 45 turn ratio on 6 volt supply you get 300 volts at the capacitor which can kill you…. you must always short the capacitor out before working on the ign system as it will hold charge for several minutes after running.

The LED is used to prevent back current and also indicate trigger points for timing it up. These work well up to about 12000rpm on a single magnet.

Best regards,
Richard

[Roy Fisher]

I found this post interesting because I’ve been considering converting my B’ham Scott to electronic ignition but with a number of reservations. My machine is 12v and has a non standard Lucas 18D2 distributor, used originally I believe by Triumph. The distributor is new and unused so hopefully with little wear in the shaft. However it’s correct that checking with a strobe reveals that the ignition timing is far from constant. What I don’t know is if the source of this movement because of inherent problems with the distributor & its advance & retard mechanism or if the skew gears that drive it cause the problem. Or of course a combination of both. There is an electronic conversion available for this distributor which does away with the mechanical advance and retard, this function being carried out electronically, but if the skew gears are at fault then the exercise would be pointless. Does anyone have any views / experience etc. on this.

Thanks in anticipation.

Roy Fisher

[Jan Buchwald]

My intension is to get rid of the mechanical advance as well as the points. The question is, how will the electronical advance work, if the electronic unit is set up for a four stroke.
I intend to ask the manufacturers.

[Bob Mather]

Hi Jan,
With regards to electronic ignition on a Scott, although I can’t any answere questions regarding using a distributor.
I fitted a BT-H self generating electronic magneto to my 1932 blind head Flyer. It has fixed ignition timing and I set it to 33 degs. which was the maximum advance I used on the old Lucas maneto. On the road, it ran horribly below 40 mph as if the mixture was much too rich, which did not make sense. I tried both weakening the richening the mixture to extreems with no improvement just to prove it wasn’t the mixture. So I set the carb. back to where it was. I sent an e-mail to BT-H for information, but it was completely ignored.
I then retarded the ignition to 29 degs. which made a big improvement, but not prfect, so I will knock it back a degree or two sometime. All of this seems to indicate you will need much less advance if fitting electronic ignition.

Regards,
Bob Mather.

[Jan Buchwald]

Thanks Bob, I have only tried Boyer Bransden, mounted on my russian Dnepr K-750, it has electronic advance, and works realy well

[Martin Heckscher]

This may or may not be relevant but a few years ago I bought a Scott which had been fitted with a Boyer Bransden system. It ran OK, but starting was terrible. It is now back on a nice little BTH M2 mag. It runs even better than it did before, and it starts when I want it to. I am no electronics engineer, and have no idea what caused the problems, but I shall stick to magnetos!

[Mike Fennell]

My understanding is that there used to be a fault with the Boyer Brandsen electronic ignition – its efficiency deteriorated if the battery voltage dropped below a certain level, and it wasn’t that much of a drop. This made starting difficult and affected reliability. I believe that improvements have been made to eliminate the problem.

[Bob Mather]

More observations on electronic ignition. Peter Scott also fitted an electronic magneto to his Scott which has a long stroke engine,[ mine is short stroke] and although only riden a short distance the standard ignition advance seems to be OK which seems to bare out what Brian Marshall stated that the short stroke engine is more sensitive to ignition advance than the long stroke engine.
I found it also seems that any gas flow improvment work on a short stroke engine makes it even more sensitive.

Regards,
Bob Mather.

[Jan Buchwald]

Here is (part of) my correspondence with Boyer Bransden, I think I will give it a try next winter:

Question: I am having trouble with a distributor mounted Scott (6 volt) and want to change the ignition to electronic.
The distributor is a Lucas DKX2A type AX1 (Centrifugal advance commences at 300 -500 rpm (distributor) and gives maximum advance of 17 – 20 degrees at 2,900 rpm.)
The distibutor is basicly the same as used on BSA C10 -C11, but on the Scott it is running at engine speed ( two stroke engine).
I am not sure how the higher revs will influence on the advance, or doesn’t it matter because there is a spark in the exhaust stroke too.
There are room for a 60 mm pick up plate.
My idea is to use the kit for BSA singles, and maintain the distributor part.
I am aware that there are some adaptions.

Answer: If you convert to 12 volt and you can engineer a stator and rotor into your distributor I would recommend using a Micro Power box for a Z400-1000 Kawasaki along with a Micro Power dual coil, don’t use the distributor, you can have dummy wires from it. (Fire every 180 deg. this works well).. This will give about 20 deg.advance by 3000RPM and supply sparks to way over 10k. If you give us the sizes for your distributor we will supply the nearest stator and rotor and supply the Z500 kit with with coil and your bits at the same cost. I would recommend you convert to 12 volt Negative earth, the dynamo can be repolarised if positive at the moment.. Use a good quality sealed 12 volt battery.

Qestion: Thank you for the answer, but!! As the Scott is a two stroke, if it fires every 180 dg,, it will fire in the “filling” stroke, where one piston is at the buttom, having just filled the eksplotion chamber with fumes. Thats why I want to keep the distributor.

Answer:
We know all modern two strokes work like this with no trouble, also the Silk’s have run this system. On the KH250 we fire every 120 deg. the mixture is to heavy to fire unless compressed. Yamaha thought it improved combustion by ionising the air round the uncompressed plug.

Boyer Bransden Electronics Ltd
Frindsbury House
Cox Street
Detling
Maidstone
Kent
ME14 3HE

Tel: 0044 (0)1622 730939
Fax: 0044 (0)1622 730930
Website: https://www.BoyerBransden.com

[Erik]

Hi Jan,

Frank and I both converted to an electronic ignition on our 1927/28 Flyers a few years back. These were of course not of the distributor type. I used a CDI system developed by Powerdynamo.biz that has a fixed iginition point (do not ask me how many degrees….). In my case I also used a toothed belt to drive it from the flywheel. The unit was fitted in a converted BTH magneto housing and does not require a battery. Franks was the same but in a custom housing and driven by chain.

Both Scotts started and ran very well with it. I had a whole article on this on my old website but have not yet have the time to convert that to m new site. I will try and do so soon if you are interested.

Cheers,
Erik

[Jan Buchwald]

I am interested, but I would like to have the advance too.

[Bob Mather]

Up date on the ignition timing with the electronic magneto. I got down to 21degs BTDC before it ran OK with no loss of perfprmance. Peter Scott with his long stroke which went flat below 33degs BTDC with the old Lucas magneto is down to 26
degs BTDC and the engine is much happier now.

Regards

Bob Mather.

[dave bushell]

Has anyone tried fitting magnets or tab to a flywheel or even holes through the flywheel to trigger a device for electronic ignition purposes? In a simple installation it would give fixed timing only, but it would be possible to make the triggering device movable to vary the timing.
Dave

[Erik]

Interesting idea Dave to use the flywheel! Seems logical and doable. So who will try first 😉
By the way, the system Frank and I have on our Scotts also uses a 180 degree spark which is no problem at all.

Cheers,
Erik

[Author]

Posts