Poor starting on new Amal and BTH Magneto

[Mark Fisher]

Just to throw something else into the mix, I fitted a thorspark system to my ABSAF Gold star impostor bike, works really well. It is a very simple system that uses the magneto to turn a small alloy fixture that has a couple of small magnets fitted to it. The points etc are removed and this leaves space for a small stator (I think thats what it is!) that replaces the cam ring. This moves with the retard cable just as the cam ring did, the advantage of this is that if the battery is a bit low your timing is not affected like with a boyer system which goes to full advance in a low voltage situation. The disadvantage is that you don't get automatic advance! So far so good with this system and it is very simple and doesn't even have a magic black box. This system should work well with a comet, I found that the starting was far better than with the mag. However the BTH on my shadow is still my favourite system, 17,000 miles now and I haven't looked at it since the day i fitted it!
mark
PS My apologies to Rip...I should never post on websites when I'm having a bad day.

 

[Magnetoman]

I fitted a thorspark system to my ABSAF Gold star... it is very simple and doesn't even have a magic black box...

The Thorspark actually does have a magic black box. If the trigger circuit in that box fails (and/or the battery goes dead), so does the spark.

The unit sells for ~$300 (which is a lot for a coil and a couple of semiconductor components) and the company's web site says:

We have developed this product as we have had several magnetos re-wound over the years, and none has lasted more than a year.

I don't intend to sound harsh, but what this says is the electronics for this were designed by someone who did not understand electricity well enough to realize that the reason for the failure of their rebuilt magnetos was the rebuilder they used, not the magneto.

Anything that provides a strong enough spark will work on an engine as long as it supplies the spark. That's not the issue. The problem with all such "modern upgrades" is the market for such ignition systems is incredibly small in the global scheme of things, so all of them were developed by well meaning guys in their garages in the evenings. The people selling them all say that they are reliable, no complaints, only praise, etc. Maybe yes, maybe no, but certainly none have been independently tested with any kind of rigor. Be that as it may, a properly rebuilt and remagnetized Lucas magneto using the right components will be every bit as reliable as any of these "upgrades" claims to be.

Many times the solution to a difficult problem becomes clear once it is understood what the actual problem is. In this case the actual problem isn't to find a reliable modern replacement for the Vincent's ignition, it's to find someone who can reliably repair a magneto.

 

[Big Sid]

All good stuff clearly stated . Actually the series D Victor ignition device is a fine piece of equipment having its own internal advance mechanism thus a perfect breaker unit . Actually quite like the twins D Dist. except it lacks the rotor section and its dedicated cap .
A very few other singles used this unit as well but they are not easy to find since Price left the scene . Still with a coil and power supply and she's off running sweet as a whistle .
Small and light and having only a single wire connection what could be better ? Sid .

 

[Mark Fisher]

Mr Magnetoman, I take your point, about the repair situation with the magneto, indeed my matchless runs and starts just fine on its lucas mag, and I have had it about 8 years with zero magneto issues. However in the case of the ABSAF goldie it was just quicker and easier than sending mags back and forth thru the mail....when i get the time I'll get it fixed properly. In the meantime this solution works for me, in fact I'm about to take it for a thrashing as soon as I'm done with this. Less than a thousand miles on this engine so it is too early to make statements about reliability/ longevity of the thorspark system. As for the black box, I get it, what I was really trying to get across was the fact that there is no SEPARATE black box with the extra wires that inevitably come with it. I guess we will see how it goes.
mark

 

[Bill Thomas]

Hello Mark, Can you give us the web site, Cheers Bill.

 

[Magnetoman]

I take your point, about the repair situation with the magneto,

To state it another way, with a standard C-Series Vincent you rely on the Lucas magneto to provide the needed sparks. With a D-Series Vincent you rely on the Lucas dynamo to do this. With a "modern upgrade" you rely on both the dynamo plus a piece of electronics designed and built in someone's basement. A chain is only as strong as its weakest link...

It's not that I'm opposed in principle to modern electronics on an old motorcycle. Far from it. I put a Lucas Rita on my Triumph Trident shortly after buying the bike. In that case Lucas had stuffed one too many sets of points into a housing that really shouldn't have more than two sets in it, so the Rita truly was a significant upgrade, not just a change. I built a Zener-based clipper diode array to make the headlight last "forever" even at high rpm on one of my ET-ignition equipped BSAs. However, in that case I picked the Zeners myself relying on the specifications and testing procedures of a mass-produced component from a major electronics manufacturer, not on whatever semiconductors some guy working in his basement thought would be good enough.

The modern history of replacement classic bike ignitions is littered with the failures of well meaning guys who thought they had produced a better mousetrap. I certainly haven't examined them all, but I have been called on to try to repair three different ones. The construction of all three was what one would expect from devices produced in basements, so it wasn't surprising to me that they failed. However, once you understand that the reason your Lucas magneto isn't reliable is because it is 60 years old, not because it is intrinsically unreliable (or inferior because it was built to a price by Lucas, or is of an obsolete design, or any number of other myths), then the problem becomes one of getting it properly refurbished it so it will be good for another 60 years.

 

[Comet Rider]

Hello Mark, Can you give us the web site, Cheers Bill.

Bill

http://www.sussexmotorcycles.com/thorspark.html

Hope this helps
Neil

 

[Big Sid]

Difficulty in starting is very dependent on where your firing point is on full retard , if too close to TDC this alone can make starting
A very chancy thing . She should break the points about 6-7 degrees BTDC , not closer . So check where yours fires the plug at idle rpm , that's where it starts when booted over .
Easily advanced with a D Dist , just rock the ign . head a wee bit back towards the front cylinder , but also with a magneto . Just open the point gap a couple of thou wider than normal , or where it's at then . Does the trick ! Sid .

 

[Mark Fisher]

Update on the thorspark on my ABSAF goldie, it still works fine and (I know it's hard to believe) I can start it first kick from cold!!! This is good because my right knee is made of titanium and I don't want to mess it up. The key is to give it the right amount of retard when starting, just like a mag. Still not enough miles to give any longevity/reliability judgement, but it works well and the bikes runs beautifully, I really do think it would do well on a comet. Getting more miles on it right now as my shadow's clutch has detonated!
mark

 

[vibrac]

Fans like me of the BT-H (and critics) may care to know that BT-H were at The Stafford show and selling new improved coils for the BT-H magneto at £15 each and old versions at £5 having 2 BT-H and no trouble I picked up two old ones for the toolbox (paddock van)