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E: Engine Comet Magneto Rebuilder Suggestions


James B

Website User
VOC Member
Hi,
Ongoing fun and games with the comet. Has been a long hard slog to get to running right - but read on...

Got it running about a year ago now. Have clocked up a few hundred miles since then but it’s never been quite right

Fooled around with the carb for ages - got that sorted eventually by making an external indicator pipe so I could set the float level properly - it had been way off

Had the classic ‘dodgy capacitor’ symptoms from the mag. Did a load of research and found the right capacitor to replace it with (modern paper/polypropylene) and rebuilt myself.

Boy did that run better! Started easily, revved nicely, idled well. I thought I’d cracked it, but the danger of hubris...

Took it for a good long run today. About 20 miles in started misfiring, then died and would not restart.
An hour later it had cooled and it ran again.

I can only conclude that there is a heat related failure in the windings, since the capacitor is known good.

Rewinding an armature is definitely beyond me - does anyone have a personal recommendation for a mag rebuilder?
(I’ve searched here and found some leads - just wondered if anyone had a recent good experience they could share?)
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Hi,
Ongoing fun and games with the comet. Has been a long hard slog to get to running right - but read on...............................
Had the classic ‘dodgy capacitor’ symptoms from the mag. Did a load of research and found the right capacitor to replace it with (modern paper/polypropylene) and rebuilt myself.

Boy did that run better! Started easily, revved nicely, idled well. I thought I’d cracked it, but the danger of hubris...

Took it for a good long run today. About 20 miles in started misfiring, then died and would not restart.
An hour later it had cooled and it ran again.

I can only conclude that there is a heat related failure in the windings, since the capacitor is known good. ..........................
Might be worth checking that your new capacitor is still actually functioning correctly before you have it totally rebuilt.
 

erik

Well Known and Active Website User
VOC Member
Think about BTH and Pazon ignitions. this is an other solution leaving a big hole in your wallet. Erik
 

Marcus Bowden

Well Known and Active Website User
VOC Member
BRIGHT SPARK, look up on line , they developed a condenser that fits under the fixed contact breaker so can be replaced at the road side. Read their write up and they explain every thing,give a price on every thing or sell you the special tools to do it yourself. All reasonably priced as I've had three pre-war Lucas twin mag / dynos done, BTH pre-war single mag / dyno and three post war twin mags. A new ATD is more costly than the work done on any of the mags,

good luck.
bananaman
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
I installed a Thorspark on my BSA Goldstar. It works really well. They have a 6V version and it draws almost no power. On the BSA it was easy to hide the coil in the toolbox. It might be hard to find a place for the coil on a Comet.
 

erik

Well Known and Active Website User
VOC Member
Hello Marcus ! I tried this capacitors with no real fun.To my mind it is only a home on own wheels solution.Regards Erik
 

Marcus Bowden

Well Known and Active Website User
VOC Member
Erik my handsome, I'm not really sure what you mean by "To my mind it is only a home on own wheels solution.""" To fit one of these capacitors the armature must be removed from mag, split open and old capacitor removed and live wire led to points, depending on how the capacitor fails will an Easy-Cap Condenser work just by fitting the new Easy Cap under fixed points, as the system can fail with open or closed circuit. That said I have been dealing with them a few years now and their longest surviving Easy Cap was 20k miles a few years back on a BSA as to my knowledge they haven't had a failure yet.
bananaman.
 

bmetcalf

Well Known and Active Website User
VOC Member
Oldhaven here on the Forum has posted about PowerArc ignitions.

See a new post from Oldhaven here.
 
Last edited by a moderator:

nkt267

Well Known and Active Website User
VOC Member
Hi,
Ongoing fun and games with the comet. Has been a long hard slog to get to running right - but read on...

Got it running about a year ago now. Have clocked up a few hundred miles since then but it’s never been quite right

Fooled around with the carb for ages - got that sorted eventually by making an external indicator pipe so I could set the float level properly - it had been way off

Had the classic ‘dodgy capacitor’ symptoms from the mag. Did a load of research and found the right capacitor to replace it with (modern paper/polypropylene) and rebuilt myself.

Boy did that run better! Started easily, revved nicely, idled well. I thought I’d cracked it, but the danger of hubris...

Took it for a good long run today. About 20 miles in started misfiring, then died and would not restart.
An hour later it had cooled and it ran again.

I can only conclude that there is a heat related failure in the windings, since the capacitor is known good.

Rewinding an armature is definitely beyond me - does anyone have a personal recommendation for a mag rebuilder?
(I’ve searched here aI use tonynd found some leads - just wondered if anyone had a recent good experience they could share?)
I use Tony Cooper in Halesowen..I've had 6 mags done by him.
 
Last edited by a moderator:

erik

Well Known and Active Website User
VOC Member
Hallo Marcus! hte capacitor can stay in Play .you cut the wire to it and that`s it.I tried this System on the workbench and the spark was really weak and the Points were firing.You can see this in complete darkness.The new in rotor capacitor made a better spark and no Points firing.This is only my experience.Erik
 

James B

Website User
VOC Member
Hi

Thanks for all the replies everyone

Interested to hear more about the thorspark-
I like the ‘independance’ from the dynamo that the magneto gives - but also like that the thorspark is off the shelf and likely therefore the only way I can get the bike running in time for the distinguished gentlemen’s ride at the end of September

J
 

b'knighted

Well Known and Active Website User
VOC Member
I fitted Thorspark on a Comet with an original Miller dynamo providing 12v through a Vreg2a.
If I remember correctly the Thorspark trigger replaces the magneto cam with it’s exciter replacing the rotating points. This means that the existing advance/retard system, whether it is manual or by ATD, is retained. This was done with the mag still mounted on the bike. I mounted the ignition coil on the back of the F106 between the battery and the horn and powered the system from the LED rear light circuit so that the bike can only be ridden with lights on.
 

James B

Website User
VOC Member
Interesting. I’m running original 6v at the moment, but using a dvr2 regulator so could convert to 12v. Bulbs should be straightforward but I wonder if the altette horn can be converted

Or I could try the 6v thorspark

Decisions decisions ....
 

mercurycrest

Well Known and Active Website User
VOC Member
Interesting. I’m running original 6v at the moment, but using a dvr2 regulator so could convert to 12v. Bulbs should be straightforward but I wonder if the altette horn can be converted

Or I could try the 6v thorspark

Decisions decisions ....
The horn will work fine 12v.
 

Robert Watson

Well Known and Active Website User
VOC Member
I have two aftermarket (Italian) Altette look-a-likes. One is a 12V and the other 6V both running on 12V. Now you know why horns in cars come in pairs with different tones!
 

Glenliman

Well Known and Active Website User
VOC Member
BRIGHT SPARK, look up on line , they developed a condenser that fits under the fixed contact breaker so can be replaced at the road side. Read their write up and they explain every thing,give a price on every thing or sell you the special tools to do it yourself. All reasonably priced as I've had three pre-war Lucas twin mag / dynos done, BTH pre-war single mag / dyno and three post war twin mags. A new ATD is more costly than the work done on any of the mags,

good luck.
bananaman
Marcus, my experience with the Brightspark Easycap replacement capacitor on a BSA A 10 has been much the same as yours, although not so many miles have been covered yet.
Before the repair you could hear a tone change in the engine once a certain heat was reached in the mag. The engine would develop a flat sound and you dare not shut it off until back home, as restart was impossible until fully cooled.
That's all in the past, it starts easily hot or cold now.
The old capacitor was removed as you described.
Glen
 

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