crankcase ID

Coil ignition  600cc  Alternator model  with distributor   late 1950's  or early 60's   most likely in a slimline frame , could be a standard or deluxe .  Some of the last widelines had coil  too I think.  looking at some engine numbers makes me think this could be  made 58/59  so could be wideline or early  slimline.  

Hi Terry,   I have had mags and Dissies,  If the mag is providing a good spark at kickstart  speed ,I would stick with it.  Dissies have their own issues and  seem a bit flimsy and cheap compared to a mag. Easy starting is better with a strong spark  and plugs  benefit from a good spark  if they are getting a bit sooty from  wet sumping etc.  Getting the mixture right  makes a huge difference to first kick starting  as I have found out recently ,this has become very important to my continued riding on the 99  as I have some issue with a very weak right leg.  One feeble kick and its all gone !.   I have Augmented my 12v dissie  with  a cheap electronic  booster box (Boyer) that kicks out a strong spark.

It's not unusual for a cam ring to be slightly out of kilter and not 180deg.

Splitting the difference ie 1 pot +2deg, 2nd pot -2deg was the usual recommendation (not factory I hasten to add). Shouldn't be an issue unless you've got a real firebreather, wild cams etc and so more sensitive to ignition timing.

My 99 is from 1959 with engine number 3659 - so quite close to yours Terry.

Mine came with a distributor and the factory records confirm that it was a distributor/coil ignition bike.

I have fitted a Boyer which goes inside the distributor and does away with the unreliable advance retard unit.

40 years ago I seized (piston nipped) a magneto 99 on my way to the Isle of Man and subsequent investigation found that the timing was 6 degrees out of sync between the two cylinders.

Hi Terry,

As Robert says, getting a 'distributor' is good condition can be challenging too, as is finding a good mag reconditioner. 

Another option is that there are mag replacement kits that use what looks like the 650 Mercury ignition housing available from the big suppliers. Not for the purists obviously, but I use one with a Boyer installed (I fitted a compact double ended coil as well) and you get super smooth idle, first kick starting, zero maintenance* and you can happily run with resistor type spark plugs and caps as well.

The units have advance curves built into the electronics box too. Only 'downside' is you will need to convert to 12v, but then you will be able to get bulbs and the like much more easily.

When I did mine 20+ years ago, they were significantly cheaper than a decent mag overhaul. Have no idea what the relative costs are like now though, and nowadays you can also fit other (e.g.Pazon or Tri-Spark) ignition systems to them if you prefer.

Hope this helps,

George

*zero ignition related maintenance anyway...

You might well find the amplifier digital bit is OK  and you just need the trigger assembly?

Nothing to lose asking. Might get you a couple of rungs back up the snake!

Regards, George 

Is it possible to fit a new BTH electronic mag. ?

If it’s proved good you can fit or sell with a test report. If it’s bad you can choose your path….

J

While we are on the subject of ID  numbers and letters ,It might be a good idea to tell owners that  Engine/frame numbers on orriginal and  unmolested bikes  don't always agree with the orriginal log books and computer records  due to Factory/dealer cock ups.   If you find a discrepancy  should you advise the DVLA ?  .I would not dream of it ,god knows where that could lead.  I have a good example in my 99. . Now that no one inspects the things  ,let sleeping dogs lie.  The  EU inspections of transported machines could be a problem  if machine and paper do not match ?.