BT-H Mag

[deejay499]

I was quite happy with the original set up on the Prince outfit, but the problem was that having sidecar fittings as well as the 'D' crash bars, it was nigh impossible to get to the points. This was not too bad in the garage but when I had distibutor problems on a complete unlit road at night, I thought the time had come to put on a BTH. I have been very pleased with it though did not think starting was as good as with the original set up, sometimes taking 3 - 4 kicks to get going. Now is seems I can only look forward to the problems mentioned above and at the very least had better get a couple of spare coils.
Thanks for all the input folks.
Cheers, Dave

 

[nortonpower]

Had a customer in to fit the brand-new BTH. It started easily and ticked over like a clock. He rode the bike for 300 miles and reported everything is perfect. A day later he could not start it anymore. No spark at both plugs. Changed plugs and the bike started again but ran crappy at low revs so he came to my workshop again to check the timing. I strobed it and found 16 degrees advance ON FULL RETARD but still only 34 degrees fully advanced - so definitely the BTH was faulty. Sent it back to Mr Harris to be checked, tried to get a definite answer on the setting for full retard which he refused to give.... Got the BTH back with the report that everything is perfect inside only to find that it still had a very weak spark despite changing the coil. Put it on the bike and it was hard to start and when finally burst to life the full retard showed those same 16 degr with lousy running engine. Harris didn´t want to exchange the crappy magnet nor did he help in any way to locate the problem and fix it. As my customer was very upset but couldn´t get his money back from Mr Harris we opted for a Grosset ignition and Alton to get the bike running properly. Now it works as desired.
When talking to Terry Prince on the saltflats he said he stopped selling the BTH´s as he had too much problems with them. One of his friends, a gifted electronics engineer, took a BTH apart and said that its all chinese stuff in there and it would need a complete new assembly made from proper components with tighter tolerances....
John Mc Dougall reported the same: he couldn´t get a Goldstar to run properly on the BTH so in the end after a couple days fiddling with timing and jets he put the old Lucas magneto back in and all problems were gone.
I have used a homemade points ignition in my HRD with good results but have modified a Boyer a couple years ago which works just as well.

Hartmut

Hugo Baumeler (swiss Vincent workshop) recommends the BTH´s only for racing - seems he has had a few problems as well....

 

[vibrac]

Howdy Chaps,

BTH's - The mounting strap for the coils places them with plug wires forward and primary wires projecting rearward in very close proximity to the engine cases. Between engine vibration, flex in this mounting arm and a tendency (especially if less flexible thick copper core plug wires are substituted) for the cowl to push the whole plot rearward, you run the risk of rubbing the wires through and experiencing a short. I try to bend the pins outward slightly to provide running clearance for the wires away from the case.

There is no reason you have to fit the coils down there, after all the naked D has its Lucas in a most conspicious place. we fit 4 (yes 4) coils under the tank on the racing Egli .
You cant see a thing when the tanks on (you see now even I am on that hide the wires kick) what is it about the obsession with hiding wires and electrical gubbins the pain I suffered at work with wires to computer terminals having to be hidden I think its a primeval throw back to a fear of snakes...

 

[Peter Holmes]

So what is the solution? I have also spent my five hundred+ pounds and I am undecided what I really think of the unit, I would definitely say that my bike (Rapide) does not start as easily or run so well as with a Lucas KVF and with the benefit of hindsight I really don't know why I decided to change (upgrade?) to a BT H, after all I only had one magneto failure in 40 years of ownership, another thing I have difficulty getting used is there is barely a visible spark, not a bit like the KVF which was big and blue on both cylinders, looking back I think it seemed attractive that it is dead easy to time and also that the spark was guaranteed to be exactly at the correct degree split 50 or 310, I will expect a comment from Trevor on that one, unlike the slip ring on the old mag, the jury is definitely still out, but what is the best alternative please. I notice on a previous post that it was intimated that the components were all Chinese and therefore junk, I think we need to be a little careful here, I am sure plenty of junk does come out of Chinese factories but a lot of very high end technological stuff does also, take a look at just about any Apple product you may own or your very expensive camera or flat screen television or mobile phone. So is the answer Pazon or Grosset or a Dave Lindsay rebuilt KVF, but far more important than all that, what are we all going to do when finally our NOS supply of ceramic coated KLG 50 spark plugs runs out and none of us will be able start or run our beloved machines at all.

 

[Bill Thomas]

Hello Peter, Don't you like the D distributor ?, I am hoping the bloke in MPH still does them as I would like one for a Comet project, Cheers Bill.

 

[vincenttwin]

I have had one of Tony's BTH mags in my A now for 12 years ,and the little coil is ratting around behind my tool box as I never have mounted it ,
it is a 1-2 kick starter, Tony says the only thing that could be china made, might be a few lots of magnets,he had to use.
I also have one on my Twin Vincent and that bike sits in a shed for months and always has a great spark.
So I am very happy with the new BTH's .

OF course a new BTH can not fix worn out carbs or wore out valve guides and the modern crap fuel will go bad in a few months


cheers
Peter

 

[vibrac]

three Vincents + 6 coils+ 3 BT-H mags =1 satisfied owner

Coil ignition? No if its not a car alternator, I'd rather trust a BT-H than a dynamo anyday

 

[Simon Dinsdale]

The only time I failed to get home due to faulty ignition was when using a modern BTH. I am keeping with coil ignition which is simple to work with. As for dynamo's, it's usually the regulator that is the weak link. Dynamo regulators ltd (formally Manortech) make a reliable unit when attached to a well built / maintained dynamo.

I would rather trust coil ignition and a dynamo over a BTH any day, but others may have had different experience.

 

[Albervin]

The spark may look thin and weak compared to an old coil or magneto spark but it is the same as on most modern CDI ignition systems. It will work much better on high compression and
oily engines than a fat blue spark. I believe my BT-H has improved my fuel consumption and throttle response.

 

[davidd]

As I understand these electronic ignitions, they either make a spark or they do not. The "fatness" of the spark is not really relevant. Like Tim, I have used the BT-H for racing and it has worked well. I would strongly urge any Vincent owner to have a stock magneto in perfect repair sitting on the shelf while they have the modern ignition of their choice on the bike. The original problem reported in this thread does not sound to me like an ignition issue if there is spark as reported and the bike is not continuing to run. I would install the original perfectly rebuilt magneto to see if the ignition is the true source of the problem.

I will say that I am unhappy with these modern ignitions in that they cannot be checked for performance. We all understand how to make a mechanical magneto work, at least in theory, but the electronic components are a mystery to the average or above average mechanic. I have mentioned in another post on BT-H that I think it is best to check the timing with a strobe so that you understand where full advance is in relation to the timing pin and the backlash in the system if you are concerned about correct timing.

David