1958 99 with alternator and magneto

The 18d2 distributor can snap its advance and retard springs and then explode.  Mine did when only a few years old. Amazingly it did it when I was working in Upper Regent St W1. All I had to do was walk into the Lucas office accross the road and order a new Dissy!.and fit it in the kerb on Regent St!. The  washer behind the sprocket can wear and allow the rotor arm to dissembowel  the cap.New pattern" Lucas" caps are very prone to this. Another trip accross the road. A cheap old mag from an earlier 99 was soon in place. My current 99 has a Dissy ,I'm still living dangerously ,but there is a mag in the shed. If the bike was built with a mag then it won't have the PSR8 switch. or C on the case.

My 99 originally had a distributor and coil which were alarmingly unreliable. I rapidly replaced them with a K2F and have no regrets. I particularly like the fact that if I have an electrical problem the engine keeps going - as in the time the rectifier failed near Shrewsbury on my way to Norwich one evening. Just a pilot light to see by but the engine being unaffected kept going and got me there.    

Can't help with original issue unless to suggest maybe the odd magneto was lying around at the back of a cupboard and was just used being 'recycled' in advance of current trends. I am like the comment above my 99 has a distributor and while no problems to date my 57 Enfield Bullet with a Lucas SR1 has soldered on for the 15 years I have had the bike with no issues. Now at 60 years old will get it serviced, It saves me worrying about batteries as not needed given only used in day time and starts easily even when it was left in a damp garage for about 4 years with long spells between starts. May keep my eye out for a K2F if I can find one. Regards, Hugh   

Has your magneto got a s/n plate on it as K2F's have a date of manufacture on the plate normally 3 digits giving month & year.

1958 and 59 were very interesting times at Bracebridge. Especially with the variety of models being churned out with the 99 engine onboard.

The engine was modernised with Alternator powered electrics and most owners of new  99 engined bikes (plus the odd 88) got coil ignition and a distributor to play with. But not if your new bike was a Model 77 or a Nomad. The former kept a dynamo and magneto while the latter got an alternator and magneto. Both kept the ancient hefty brazed lug frames but the Nomad did have twin carbs. Though it was not available in the UK. Also well into 1959, if your 99 was an export machine heading for the French Police Force it too would have kept a dynamo and magneto.

For those people with a few bucks to spare, a new 99 Dominator could also be obtained with a very tuned engine plus twin carbs, plus an alternator and magneto ignition. All at extra cost. These bikes were called Specials and were produced right up to the start of 650 production. Then they were renamed Sports Specials but kept the old cylinder head and were given coil ignition or the option of a magneto with a manual advance retard. In those days although coil ignition had become the new norm of car engines it was not too reliable on motorcycles. Bike batteries kept losing their charge and the emergency start position on the ignition switch just never seemed to do anything.  So as many posters above have stated, it was not unusual for the 99 distributor to quickly get the boot and be substituted with a battery free magneto. I did it.

Alans post about an  ID plate  will help the detective work as it could tell if the mag has come from an earlier bike  or even another make of bike.

With no ignition load on the battery its possible (depending how the alternator is connected) that your battery would get more charge than is healthy for it. A modern reg/rectifier would  be a good upgrade.

[That was the one with two Cadbury's Flakes!]  Mine was registered with Tayler Matterson's in July 1959 and was a "99 Special" - twin carbs, HC pistons, large inlet valves, chrome mudguards and fully enclosed rear chainguard.  Probably a polished head too as the first owner seemed to have gone for most of the extras shown in the red text at the back of the 99 Spares list for 1959, much as Phil says above. There was no Magneto option listed though. John Hudson identified the bike for me when I corresponded with him asking numerous questions in 1965. 

It came with a standard distributor, which gave me a few problems at the beginning so I swapped it for a K2F mag from my 1955 88, which I had dismantled and sold parts from after a prang.  I sold the frame to an I.o.M. racer (No idea who!) as he was fed up with the Manx frame cracking at the top rear loop as I recall - but it was 55 years ago!   I sold the QR camshaft to Barry Lawton (Syd's son) who intended to put it in his Domiracer. 

I still have the distributor and the mag and was thinking of putting the dissy back in the 99 as I will be going for Concours.  I changed the PRS8 switch for an 88SA - which I still have, plus three PSR8's!  It gives me good choices.  I do like the PRS8 switches - strange aren't I?

I do remember, when I was cleaning up the mag to put in the 99, that I rotated the sprocket by hand as I pressed a meths-soaked rag into the works and got a belt off it!  Don't do it!

If I want to use a distributor for authenticity I will overhaul it or get it done by an expert!

As usual, the main reason for the factory to change from magneto to simple coils with contact breakers was cost.  The mag is infinitely superior - count yourself lucky to have one.  No battery to go flat, no charging circuits to go wrong, no coils to vibrate themselves to pieces or cook themselves to death should you accidentally leave the ignition switched on in  the shed.  Even today, piston engined aircraft use them.

It all depends what you want from your bike. Is it something to polish, show off and take to shows or is it something to be ridden?

No prizes whatsoever for my opinion on the subject.

With the addition of  an electronic box  the 18d2 becomes just  that bit more usable. Points condition and gap become less relevant and the spark for kickstarting  will now outperform the magneto .Very usefull for those with health issues. Timing is still afected by the points gap as it changes and I immediately can feel a loss of snap in the acceleration if it retards a few degrees and a slight tendency to kick back if it is advanced.I must be lucky with my dissy as there does not seem to be any timing variance between cylinders.As it ages wear may make the timing less precise ,so long term I will be looking to using an electronic pretend magneto.

Good point Gordon and one which I don't know the answer to!  The truth is I'm 74 and haven't ridden a bike of any sort for about 40 years!  At my age balance isn't so good.  Put it this way - on telly I've seen American Cops ask a driver to stand on one leg to prove he or she isn't "D.U.I".  I don't think I would pass!  I did ride a pushbike very briefly about 2 years ago and have one I'm storing for a friend so I will try it someone to test my balancing ability.

So it's more likely that I will do very low mileage and still go for Concours - a challenge eh, but not mutually exclusive?  Long hard riding might prove problematic with a distributor system but that is unlikely to happen.  I'm thinking of trying a simple electronic ignition add-on, as I've mentioned before.  They worked on my Mark 10 Jaguar and my Bedford CA Dormobile back in the 70s.  They did away with points - which was a good thing.

..or not as you prefer. I can put Boyer ignition into an 18D2 and 18D1 and I have rebuilt caps for the 18D1 From this the ignition point can't change and both cylinders are timed exactly the same.

Point-if you are travelling about with a failed battery system then no horn, no stop light, no lights. What do other road users think of the old twit on a rubbishy old bike? Sorry Gordon.

But going back to the original problem. It is simple enough to convert an 18D2 to magneto. Remove dizzy, with its mounting platform and its drive sprocket (no advance/retard) and parallel shaft. Fit magneto-same three bolt holes, drive sprocket is now tapered it might have an A/R built into it (or manual A/R).Done

To convert the other way, remove magneto replace 18D2 with its mounting and its parallel shaft drive sprocket and the ignition coil. But now you will have to arrange an ignition switch-PRS8 maybe if you want originality.

Not common now but it was back in the 1970's when the above incident took place. Not turning up at a RAF base when expected was not looked upon lightly. As mentioned, journey completed on pilot and tail lights with stop light and horn both functioning.

I'm still a fan of magnetos purely for the reliability. It's exceptionally rare for a magneto to fail outright. You hear complaints of poor starting when hot, often an early indication of capacitor failure, but it gives you time to sort thing out rather than leaving you stranded out in the wilds if your charging circuit fails. I'm still running the same mag on my 99 which was overhauled 40 years ago and it has clocked up a lot of miles in that time, approx 100,000. 

So you had that mag changed as a we bairn, as per your picture above!!

Yes these dodgy rides were often done some years ago, hopefully with age comes some responsibility......

I like the Electrex system which is completely modern tech and lets you leave a dummy mag or distributor in place.

The sparks are independent of the 65W alternator.

Very easy to fit with an alternator, not easy with a belt.

I like the Electrex system which is completely modern tech and lets you leave a dummy mag or distributor in place.

The sparks are independent of the 65W alternator.

Very easy to fit with an alternator, not easy with a belt.

I remember Police models had, in Sussex everything. Dynamo, alternator for the Radio, and Magneto for easy stating to chase Mk2 Jags.

Some M20s also had alternator and dynamos. Didn't catch many Mk2 Jags though!