B-TH magdyno

[PeteL]

An old thread,
but I'm interested as to peoples experience of the B-TH (Alton) magneto. For my '52 VH.
Has the "2 bolt hole" fixing proved to be a problem?
Just having had bearing failure on the Lucas M01 I'm a bit disillusioned. I must have had about 10 bikes over the years with Lucas mags. Various problems, but nothing like this disaster.
I know the new mag is expensive but I'm hoping others will say its worth having.

[chris.shearwood]

but I'm interested as to peoples experience of the B-TH (Alton) magneto. For my '52 VH.Has the "2 bolt hole" fixing proved to be a problem?I know the new mag is expensive but I'm hoping others will say its worth having.

I've been using a B-TH mag in my 51 VH since 2014 although with only about 3,400 miles done in that time. On the initial installation I encountered a problem due to the mag platform not being totally flat. This resulted in the mag shaking a bit in operation. A shim or two fixed that and since then there have not been any other problems at all.
It seems to me that the original Lucas ignition system performs very well when all the components are in very good order but difficulties occur in keeping all the components in very good order! Once I got the B-TH mag installed and timed properly it has required absolutely no maintenance to perform perfectly i.e. easy, dependable starting and trouble free running.

[PeteL]

Thanks,
I'm getting my original mag back with bearing failure repaired next week. Its had a full rewind etc. recently, so hopefully it will perform Ok, but I think I start a saving up campaign for a B-TH for next spring.

[adrie.degraaff]

I still have 2 spare Tony Cooper magnets, every time i met him i bought 5 items just in case but they just keep on going.

[Vincent.vanGinneke]

Yep , nice guy..... viewtopic.php?f=23&t=12013

[adrie.degraaff]

Nothing wrong with my TC Lucas items.
I had the same BTH experience with IJmuiden simply becouse they can't find the parts.

[Dave.Thomas]

I use a BTH on my NH Trials bike, worked faultlessly for 4 years in mud/water generally . I have one on a BSA road bike too, no problems and nice to never have to remember to use the adv/ret lever

[Richard Kal]

I installed a BTH on a Super Rocket in 2008. I have hidden the coils under the "ski slope".
Very happy with the performance; easy starting and smooth running engine.

Richard

[tonyh]

Hi Folks
I have had my magdyno BT-H on for about 15 years since I made the prototype with no problems except a new clutch spring as the fibre wheel was slipping a little a few years ago. The original MO1 platforms were very wear prone but not the BT-H one. BTH Componants took over my business 10 years ago up until then I made all the bodies from castings and they looked like the original ones. Unfortunately whoever makes the ones for BT-H Components couldn't balance the castings up properly when machined so made them from solid which do not look right.
I ran a 6V dynamo for some years then bought a Alton unit which lasted 300 miles. I took it to bits and realised why. I made new drawings and sent them to Alton and repaired mine the best I Could which lasted another 2K miles ish before it fell to bits. I now run a 12V converted Dynamo which has now done many reliable miles.
Tony

[nevhunter]

The problem with the original Lucas MAG.armature is it only has TWO long screws holding the armature together and it sometimes gets a bit of run out and maybe people push and pull the sprocket getting it OFF. Running the drive chain too tight is fatal The support bearing is too far away so there's a big load on the shaft. Lucas used to say return it to them every 8,000 miles for repair. WE must be running out of good stuff to repair them with so repair costs go up and the result gets worse. The original armature is matched and then finally machined. Remachining makes the air gap bigger and the spark will never be as good as it was IF that's done.
I bought a lot of stuff from motorcycle autoelectric shops closing down MANY years ago but most of that is now used up. I don't think any replacement for most of the bits have ever been reproduced aftermarket for the majority of normally non wearing parts like ends for the generators and the end with the points on the magneto.some of which become unusable and are made of zinc rich Diemetal. Never expected to last 90 years
They DO work OK when you get a good one set up properly . I've always done all my own electrics and I'd be much more apprehensive IF I had to pay someone else who I had no prior knowledge of as to their work quality..Nev