Difference between TT BTH and regular BTH Magneto

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brett.hayhurst
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Difference between TT BTH and regular BTH Magneto

Postby brett.hayhurst » Wed Mar 13, 2013 12:46 pm

Hi, Can a Magneto guru please tell me the difference between TT BTH and regular BTH Magneto in their make-up, if anything at all.
Is my googling correct that a BTH is a Magneto designed for 4000RPM + running for long periods and if so how or what was the change.
AND, is there any difference in output between an old school Magneto reconditioned and a new BTH Magneto produced these days ?
Have also seen new Magnetos with advance curve built in but is there a way to have an advance curve adjustable at all or would it be pointless ?
Cannot find any manufacturer stating as such but maybe is can be done ?
All Magneto information in this area of my questions appreciated or any tricks from the day I would like to know.
Thankyou.
Brett

robin.parker
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Postby robin.parker » Wed Mar 13, 2013 1:29 pm

Brett,
A new BTH Mag is a thing of awe and wonder, they are self contained, self generating, electronic spark producers, can have inbuilt ignition advance provision and are far superior to our old type mags. New BTH LOOK like the old ones, but that's as far a sit goes. The competition boys love them.
New type "BTH" mags have all the undoubted advantages of Electronic Ignition, without the drawback of reliance on a Battery and Charging system.
I think they now do a replacement for the Mag bit of a MagDyno.
Do you think they'd give me a job??
Robin.

brett.hayhurst
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Postby brett.hayhurst » Thu Mar 14, 2013 1:01 am

Hi Robin,
Sounds like your impressed and if anybody from bth Components is reading they have a job for you in marketing with a corner office, large windows and a platinum credit card !.
They do look good though. Thanks.
Brett

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Postby john.whiting » Thu Mar 14, 2013 10:46 am

Wow,540 quid.I d actually be fitting my bike to the magneto,and not vice versa.I think Id be leaving that one to rich Sq 4 owners,but they dont need magneto s.Regards John.

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Postby john.nash » Thu Mar 14, 2013 4:10 pm

If you don't have a magneto, then that will cost plus the inevitable cost of a rebuild.....
I guess it also depends on what your bike's worth to some extent and also how much use you'd be getting ....
John "Josh" Nash
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2009 royal Enfield,1978 t140 bonneville, '67 CJ750, 196-ish Ural M62 outfit, 1960 k750, ''51 kH500, ''49 soon to be Ariel bobber, 47 VH twinport, '44 Ariel WNG, '43 Ariel WNG, '41 Ariel WNG and piles of rusty scrap ....

brett.hayhurst
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Postby brett.hayhurst » Fri Mar 15, 2013 2:35 am

I did have a long rant written up but have decided just to say, "this is the price us newer Ariel owners have to pay for parts that others have sitting in the shed covered in dust".
All offers of any Ariel parts for sale will be gratefully received by myself and others that are similarly the more isolated around the world trying to get another Ariel back on the road.
Brett

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Postby robin.parker » Fri Mar 15, 2013 10:15 pm

Brett. You certainly don't HAVE to pay that much, if you search and ask around, you will find a mag, ok, it will almost certainly need a rebuild which should not cost more than £150.00 and it'll be good for years. A good mag makes the difference between a nice bike and a pig, modern BTH are Rolls Royce quality, but that's always something of a luxury. Try a wanted advert. I guess carriage from UK would make such an item costly in Aussie, but they are surely around out there. What bike are you trying to get back on the road?
Good luck,
Robin.

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Postby tonyh » Thu Apr 04, 2013 4:56 pm

Hi lads
I suppose I better say something as I am the one that developed and manufactured all the new BT-H electronic mags.

Although I have now sold the bussiness and have retired about 18 months ago. Peter, the new owner is still producing them
They has there own rotating magnet generator inside and again our own CDI unit. These are analogue not digital.
This is not a problem and work very well on our old clangers. These motors do not need fancy advance curves

When you consider most folks with manual mags just retard for starting then unless they are ticking over at a junction it's fully advanced.
The electronic advance in the new mags are semi mechanical and relies on the speed of a magnet going over a coil and as the revs rise the magnet sees the coil sooner and advances the timing up to about 3000 rpm then stops advancing.
This cannot alter like most battery powered units when the voltage drops as my mag produces it's own power like the original unit.

There are no points, armatures, poor old condensers and weak old magnets cast into the bodies etc.
The magnets use the latest technology and will not lose magnetism, a major problem with old stuff.

Over the years I have made replacements for most British bikes flange and platform. The Lucas MO1 replica magdyno I made is our own casting and uses the same internals as the rest of the range. It also has new fibre gear and clutch. This also is manufactured in house as some of the new replacements gears are made of sawdust, not the correct type of Fibre.
I have also just developed a replica Lucas flange magneto which Peter will have on his stand at the April Stafford show this year.

All these take a lot of time and development and are hand made in small batches. This is not a cheap unit to make. I could have done what all the others are doing. Just buy in Pazon or Boyer units and knock up a housing for it (as I did years ago). However, you really need 12v not so good with a dynamo I know. Then if the battery goes flat, the bike won't run. This is the same for a points and battery system.

I got fed up with having 60 - 80 year old mags reconditioned and 6 months to 3 years after spending lots of cash having it done again. Yes there are guys who can put some life back in them but how long will they be with us?. My 59 NH went from 65 mpg to almost 90mpg when I fitted the first magdyno. The units push out about 25kv by the way well up with the originals.

We must remember it's 2013 and the old bikes are transformed buy a good ignition system and one which calls for no maintenance and easily timed fits the bill.

Robin, I am sure Peter would like you as his PR man and it's always nice when somebody sings your praises.
Sorry to ramble on a bit but I hope this answers some questions for you and you all found it useful.

Cheers Tony

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Postby nevhunter » Fri Apr 05, 2013 1:37 am

I'm a bit reluctant to buy into this but I will. As to not needing much change once off idle I don't find that to be the case. load and revs make using the manual advance a must, for optimum timing in most cases.. It is up to you how aware you are but there has to be some compensation for load. (ie vacuum) If you are serious. Some engines are much more sensitive than others
Magneto's CAN be quite reliable but do suffer from deterioration due mainly to moisture, loss of magnetism. mechanical wear of cam rings points fulcrums etc. Thw modern substitute sounds like a good unit. As for cost? How would you expect it to be much cheaper, as it is a low volume specialist unit.
By the time you buy a magneto (If you don't already have one) and have it properly rebuilt you wil be up for a fair bit and some rebuilds do not last long. I have some that I built in the early 70's still never having been removed from the bike and still going well but that's stretching it for luck, and they were done right in the first place when parts were more available and good quality. Stationary coils are preferred to rotating ones also. Nev.

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Postby brett.hayhurst » Fri Apr 05, 2013 3:22 am

Agree Nev, no need to be shy, even if they are "old clangers" I have never heard of a petrol engine that cannot be better with an adjustable advance curve and I would not be calling the technology breakthrough fancy either, they worked out decades ago that there is a measurable advantage.
Just because back in the day, and now, they can operate on full advance once underway, it defies basic combustion engine principles that an improvement cannot be had with different timing for changing loads and RPM. I know your thumb can do this for you on an 80 year old system so I do not understand why the "new BTH" cannot do it for the price these days.
If your a putt putt putt rider, standard is fine, but if you twist the wrist a bit, an advance curve is a definite advantage and compliments all the other performance parts you have fitted like cams, head work, exhausts and higher comp pistons.
I would like a system such as the similarly priced older Harley replacement ignition systems have a switch giving you have a selection of advance curves so as you fit parts you have a choice of curve. Gees, I even remember changing springs in Dizzys to alter the advance curve decades ago, looking back they seem high technology to a unit made in 2013 with no way to alter an ignition curve.
"The units push out about 25kv by the way well up with the originals" does not instill much excitement either, as a potential buyer I would of hoped you would have a unit these days that was definitely equal or better than a 80 odd year old designed unit, sounds like it is only close to the originals.
Can you tell us if there is any design improvement/development you are currently working on for these replacements ? I am not knocking your work or quality Tony as it does look very good but there is potential for a more advanced unit for those of us who may be looking for a performance replacement and do not already have a genuine BTH.

I still do not know the answer to my question either. Anybody ?


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