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mag. renovation

bmetcalf

Well Known and Active Website User
VOC Member
Unless the commutator and inner bearing race are looser than they should be, you will need special tools to pull them off the shaft. Usually better left to a specialist. The other question is what condenser? An NOS Lucas would probably be about to fail. Podtronics in the US will sell you a specially made one, but the items sold by other suppliers may be short lived.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Magnetos

Send it to Dave Lindsley. Be aware that magnetos do NOT last forever (a friend who races in the Manx Grand Prix has his overhauled EVERY year, my experience is that my mag, a 2MTT on a Manx Norton began to fail every three years) and that the condensor/capacitor is usually the problem. Note that racing mags are run FAR hotter then road mags, so multiplying the times above by three is probably realistic.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Magnetos

Send it to Dave Lindsley. Be aware that magnetos do NOT last forever (a friend who races in the Manx Grand Prix has his overhauled EVERY year, my experience is that my mag, a 2MTT on a Manx Norton began to fail every three years) and that the condensor/capacitor is usually the problem. Note that racing mags are run FAR hotter than road mags, so multiplying the times above by three is probably realistic.
 
B

Bikersally

Guest
Send it to Dave Lindsley. Be aware that magnetos do NOT last forever (a friend who races in the Manx Grand Prix has his overhauled EVERY year, my experience is that my mag, a 2MTT on a Manx Norton began to fail every three years) and that the condensor/capacitor is usually the problem. Note that racing mags are run FAR hotter than road mags, so multiplying the times above by three is probably realistic.

I wouldn't recommend Dave Lindsley. Rebuilt a mag for me years ago and the old Ariel wouldn't start when hot. When I eventually got round to putting it back on the road which was about 4 years after having it rebuilt I sent it back to Dave. He then told me whoever rebuilt it previously used poor quality parts! I told him he did then..silence........Based on my past experience and a recommendation from Peter Barker I have recently used Sean Hawker for a dynamo rebuilt. The whole dynamo was re-done inc the cosmetics. He supplied his own regulator which he developed himself and very pleased with the end result. Price was reasonable but most importantly it now works!
 

Prosper Keating

Well Known and Active Website User
Non-VOC Member
Most of the guys riding magneto-equipped bikes in the Paris area use Tony Cooper. I've never heard anything negative about him or his work and I've never known any of the guys stranded by the roadside with a duff mag. And they all put in some serious mileage all year around. On the other hand, the guys who fit electronic ignition systems, oddball electronic regulators and all the other geegaws advertised in the pages of some popular classic motorcycle magazines, alongside all those ads for mailorder brides, copper bracelets, motorcycle-borne undertakers and pile cushions always seem to be breaking down...

They still fit magnetos to light aircraft. Go figure...

PK
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Sean Hawker

I've used Sean Hawker to sort out a problem on a Sunbeam S7. I thought he was very good, very thorough. He not only diagnosed a problem with the M45 pancake dynamo - for which he has a test rig. Pancake dynamos can't be clamped in a vice and "motored" like Vincent-type dynamos so 90% of the usual testing procedure is oot the windae. (Worse, yir ba' is oan the slates.) He sent me a picture so that i could see what the problem was (an internal intermittent short) so I could avoid having it happen again. He also geared the level of his explanation to suit "those of the meanest understanding". If you see what I mean. I was grateful for that.
 

Tnecniv Edipar

Well Known and Active Website User
Non-VOC Member
I can add my endorsement for Tony Cooper's work. He uses many items of original Lucas test gear , jigs etc. He also hot tests mags in a special oven.

Regarding the comment above that light aircraft still use mags , this is true but the Mags used are a distinctly different animal from the built to a cost Lucas etc types used on motorcycles. I've seen a few aviation Mags opened up and they are incredibly well made. Not forgetting also that they are overhauled on a strict time schedule , the philosophy being that they should never fail in service.
As far as I understand , the reason that Mags are still used on light Aircraft piston engines is that they are independent of the planes electrical system should a failure occur there.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Magnetos

What is also true of race mags (TT and the later 2MTT) is that they were lab tested before release. Lightning mags had the lab test batch number stamped on them. What is also true, from personal experience, is that a race mag (which is spun a lot faster and gets a lot hotter than a road mag) needs to be overhauled every couple of years. Usually the condensor has failed or is failing. The condensor seems to be the weakest part of a rebuilt mag.
(I imagine - I don't know - that aircraft mags have a rather easier time. They aren't run very fast, and I doubt cooling is a problem.)
 

Tnecniv Edipar

Well Known and Active Website User
Non-VOC Member
Why would race mags run faster ? Don't all mags on a 4 stroke engine run at half engine speed ?
Aviation mags have their own hard life , vibration , duty cycle and heat. They are typically out of the airstream as in wet weather that airstream is err , wet !!
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Magnetos

As I said, I don't know, but I don't think many aero engines run at 7 to 8000 rpm. My impression is that 2 to 3000 is closer to the mark. I don't doubt aircraft mags are better made, but the design brief must be quite different. They seem to be rather bigger than bike mags: the only aero mag I've ever heard of being suited to a bike is the Scintilla. My guess is that that is because it's the only one small enough.
I've had three mag failures (three out of four DNF's) in 15 years. Each one was on a stinking hot day on a long, fast (high sustained speed) circuit. Rain isn't my magneto's enemy, it's its friend. "Oh blessed cooling rain..." but don't quote that back at me as the rain beats down on some summer rally this year. I've only ever had one road mag fail: probably old age - it was 65 years old. I can relate to that.

Why would race mags run faster ? Don't all mags on a 4 stroke engine run at half engine speed ?
Aviation mags have their own hard life , vibration , duty cycle and heat. They are typically out of the airstream as in wet weather that airstream is err , wet !!
 

Comet Rider

Well Known and Active Website User
VOC Member
Aircraft Mag's

Most aircraft mag's are rotating magnet, rather than bike mag's rotating coils. Also most (other than microlights) aircraft ignition system tend towards dual mag systems, to allow for backup in the event of failure.

From memory the scintilla system was an LT generator with either a built in, or external HT coil, which allowed for primary voltages to be as high as 400 Vdc.

Neil
 

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