Misc: Everything Else Starting Problem - Series 'C' BIG Single

[Simon Dinsdale]

To my mind it is not the best idea to use a magneto atd with ordinary points! Because of the magnetic resistance,the coil tends to "stick" between the magneto and because of that the timing is forced to retard.Especially when you start the engine the timing is retarded to the maximum because of the "sticky" magneto.Not so with points here the retarding is only by the springs of the atd unit. I hope you understand what I mean.not so easy for my to find the right words Erik

The magneto ATD goes to the retard position due to the natural rotation direction of the ATD when driven by its gear and that occurs when driving a mag or driving a basic shaft to operate coil ignition points. I have used a magneto ATD to drive a points based ignition system for over 50,000 miles and never had a problem and the bike performed just the same as when a magneto was fitted. I know other owners who have done a lot more miles (one person has done over 200,000 miles) on the same system and again no problems. In fact the ATD has a lot better life on a coil ignition points based system as it is the magnetic resistance of the magneto that eventually strips the teeth off the ATD gear as they always strip at the peak magnetic point. Also the reason for the original ATD breaking off ears is due to the banging against the ears due to the magnetic pulse resistance of the mag.

The only modification I make to the ATD is I reduce the advance range a bit so at fully retarded its set at 4 degrees BTDC and fully advanced its at 34 degrees so a range on 30 crank degrees where originally the ATD had a range of 34 degrees at the crank or 17 degrees at the ATD.

 

[Bill Thomas]

Stick with what you have Jez,
If it worked before ,It should still work,
You have a new engine and new Carb,
The carb' could be miles out ?,
Sit on the bike in " first gear ", Roll back on compression, And get someone to give you a push start,
Just to get it going,
Flood the carb' and maybe use a spray of easy start,
With the Mk2 the slide can be one size out and it's like you switched the ignition off !!,
Don't know about you big carb'.

If you want a Distributor , There is one on ebay £180 Philip Law, I had an inner c/case off him.
Good Luck. Bill.

 

[stu spalding]

To my mind it is not the best idea to use a magneto atd with ordinary points! Because of the magnetic resistance,the coil tends to "stick" between the magneto and because of that the timing is forced to retard.Especially when you start the engine the timing is retarded to the maximum because of the "sticky" magneto.Not so with points here the retarding is only by the springs of the atd unit. I hope you understand what I mean.not so easy for my to find the right words Erik

It hasn't been a problem in 25 years, Eric. Cheers, Stu.

 

[Jez Nemeth]

Stick with what you have Jez,
If it worked before ,It should still work,
You have a new engine and new Carb,
The carb' could be miles out ?,
Sit on the bike in " first gear ", Roll back on compression, And get someone to give you a push start,
Just to get it going,
Flood the carb' and maybe use a spray of easy start,
With the Mk2 the slide can be one size out and it's like you switched the ignition off !!,
Don't know about you big carb'.

If you want a Distributor , There is one on ebay £180 Philip Law, I had an inner c/case off him.
Good Luck. Bill.

Defo worth a go Bill! Anything other than trying to kick it over again. Was at a wedding at Usk Castle on weekend and never got to the dancefloor -could hardly walk. . . crawling into and out of a tent was a complete joy...

I'm still hazy about the distributor route as to what's required if we go there, options, just to know - 'Clockwise' rotating distributor for a single, or doctored D series distributor + high powered ignition coil so far if I'm getting this -

 

[Bill Thomas]

Clockwise from the Drive side, So says the Vincent book,
The Distributor Doc' talks about it from the points end, So be careful !.
I think The ebay one is for a twin, I think it will need a fibre drive pinion,
I think it will work on a Comet , Giving you a wasted spark ?,
The coil needs to be 4 to 5 ohms,
The 2 ohms is for electric ignition,
feked. com
stocks coils.
I would get it going on your B-TH first,
But that's just me.

 

[Bill Thomas]

I got a triumph Twin cam and ground one lobe off,
But as you know , Never tried it yet,
For a single, You don't need a distributor cap,
The old C11 BSA just has a cover, Feked stock them, Cheap !.

If you used a Twin Dist' and cap, Maybe have to earth one H.T. lead out ?.

 

[timetraveller]

Jez, just to try to make it clearer, without seeming to make it more complicated, this is only a single cylinder engine so you do not even need a distributor; just a method of opening and closing points and advancing and retarding the timing. I mentioned a distributor previously as it just seems to me that might be the easiest way to get what you need. All the motorcycle distributors I know of have the advance and retard built in but the idea of using an original ATD to drive any method of opening and closing the points seems quite a good one. Provided that you could make such a system then you could take the HT lead output from the coil directly to the spark plug. So given some way of housing the points, and fitting a capacitor somewhere you would be good to go.

The point made earlier about the timing is well made. This will be a high compression engine with squish bands and will only need a fully advanced timing of about 20 to 25 degrees BTDC. It will still need to be about 4 deg BTDC fully retarded for starting thus you will need less travel on any ATD.

 

[Bill Thomas]

My point is it should still start and run OK , Slow running ?,
If Jez times it at 4 degrees retarded, On what he has B-TH ?.
So I am thinking something else is wrong at the moment ?.
I had told Jez I used a plastic tube on the shaft to hold the bob weights open a bit to reduce advance ,
"D" Distributor,
When I used 12 to 1 Pistons.

 

[greg brillus]

If you are running a BTH with twin spark and say 30 or less degrees of full advance, you will never be able to kickstart it........the retarded position will be firing well after TDC and there is your problem.........we've seen this several times here on Comets running 600 top end kits and BTH mags........its a no go i'm afraid. I discussed this with the new owner of BTH about advance curves for twin spark engines, he had no idea what i was talking about.......Realising he had no clue about it all, I quickly gave up talking to him.

 

[Jez Nemeth]

Norman/Bill, thanks both -starting to get my head around this now...

Yes -presently no ATD it's all electronically run from inside the BTH electro Unit -so may need to get one of those from feked.co.uk ...it is timed adv 36-4 deg rtd from TDC (range is 32 deg for the BTH FM1C unit), single spark, and was once upon a time a 600cc TP head before major mods were carried out - lot less metal in the head than it left Oz with for sure.