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Misc: Ignition B.T.H Magnetos

Bill Thomas

Well Known and Active Website User
VOC Member
Am I right that the NEW BT-H mag's don't need any electric feed ,
Just like the old ones ?, Cheers Bill.
 
Last edited by a moderator:

vibrac

Well Known and Active Website User
VOC Member
Great product pity about the price I have one on the bench waiting to be refurbished after 10 years of Comet racing and I could get another for the road Comet, I have got an old Lucas on the road bike at the moment but I am a bit brassic for project funding at the moment things may improve I may sell the Egli Comet in the spring whan the clouds lift
 

Bill Thomas

Well Known and Active Website User
VOC Member
I thought it was just me that had that trouble,
It's very often under my Nose !.
Wish I was as keen as you, I just think a lot !.

The Wife says I am a Thinker, I think that's what She says :D

One day I must have a go at my 560 flywheels, Maybe a job too far ?.
 

norvinmick

Website User
VOC Member
i have had bth mag on my bsa for as long as they where first made may be 20 years or so when i built the black norvin i changed from mag to bth as the mag is in front and will get wet and cut out so i went to bth no problem with water the only problem i had was wen i put new pistons in i put the coils back in place and wired up one wire the other wire had blue tag on it this is the one you timed the engine on.on the coil it has a arrow with b on it. after about 4 to 6 week the bike wood start easy get up 60 65 mph and no faster. i took mag off done every thing i could the lads were saying change the carbs as i was running gardeners i was thinking about it but sent the mag back to bth they said nothing wrong put it back on run it no good above 60 65 mph after another 2weeks i sorted it it was the lead was on the wrong terminal great now i can have a good burn up. i have fitted a bth mag on my other norvin since 2006 4 plug head the black norvin since 2000 and never let me down .
 

kinsellm

Website User
VOC Member
I have modern BTH magneto on a series C Black Shadow. Works well so far, but have only covered about 300 miles so far.
Since about 2010, my brother has used them on his ARIEL HS 500 singles in all weathers, both MK I for scrambling and Mk III for road use. Never had any problems, even with the scramber being breifly submerged under water. On all these bikes we set the plug gap at 20 thou.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Am I right that the NEW BT-H mag's don't need any electric feed ,
Just like the old ones ?, Cheers Bill.
Tony, the original designer/and manufacturer of the new BT-H magnetos had a stand for several years at the Stafford Show with several of his magnetos displayed on the table. One of the magnetos was one setup for a Vincent twin. A common question asked by interested parties was "what is the spark like?" Tony would pick it up off the table (no wires connected to anything on the table) and spin it by hand producing sparks jumping with a crack 1/4" from the end of the plug leads to the body of the magneto. The next question was often "is it 6 or 12 volt? o_O
 

erik

Well Known and Active Website User
VOC Member
I have the BTH on my rapide for 6000km. no Problems.Now i fitted the BTH to my new Project.What I like is that you can fix the BTH with a pin in the early firering Position and the Retard Position is automatically Right.I choosed 34 Degrees btdc.Erik
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I was asking for a friend, A new person to Vincent's,
I am out of touch and prefer a Distributor myself.
Cheers Bill.
Dear Bill,
Not a reflection on you. I just found it amusing that people couldn't understand how something could work without a battery. I guess a younger generation have never had anything without a battery. The way things are going all vehicles will have a big battery and no engine that needs an ignition system.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Thanks Ed, I just like to check my memory and the fact that I haven't fitted one myself.
He fitted one against my advise, He already had a distributor, But someone had welded the inside up !!,
And guess what, He is in trouble ! , With the BT-H, Hopefully it's just an easy fix,
I have nothing against the BT-H, Just the cost !.
I just thought for Him it would be best to stick with the Distributor,
But I can only say what I would do.
Which the Wife would say is always wrong :D .
Cheers Bill.
 

Chris Launders

Well Known and Active Website User
VOC Member
I have had one on my twin for 15.000 miles, I had one CDI unit go down a couple of years ago, it was replaced and back on the bike within a week, other than that not the slightest issue.
However I must say I have had a refurbished Lucas Magneto on my Brough Superior for the same mileage with NO problems at about half the cost.
I now do my own magneto rebuilds as far as possible only having to outsource the armature rewind and the final remagnetise.
 

erik

Well Known and Active Website User
VOC Member
The disadvantage of a traditionel magneto is a weaker spark on one cylinder and this means less power on this cylinder.Erik
 

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