BT-H Magnetos Ltd.

Jess Stockwell in the U.S.A. sent  this comprehensive illustrated account of fitting a new BT-H magneto to his Vincent.

After five years of trouble with the standard KVF Vincent magneto, I finally had enough. It was rebuilt twice during that time by reputable technicians, yet still was a complete bear to start and sometimes would not start at all. If I did finally get the Beast started and went somewhere, when I wanted to make my way home, I didn’t trust that it would restart to take me home. This is a death sentence for any motorcycle. As soon as they become unreliable, they become relegated to sitting …“elevated” to the position of garage art. I had tried everything that I could think of and was at my wits end.

The more I read about the initial design of the KVF magneto, the more I thought that even in perfect condition they were really designed to be optimal for a parallel twin.  Also, the design was really about 75 years old.

I thought about converting my Vincent to electronic ignition, remembering that it was the best thing I had ever done on my old Shovelhead H-D. After the conversion on the Shovel ten years ago, and to this day, the thing fires on the first or second kick, seven days a week, three hundred sixty five days a year. Even with my success on my old shovel, I still had some doubts about suitability for my Vincent.

Electronic ignitions draw some current, so if charging fails, spark fails and British electrics were not known for being bullet-proof. Most modern electronic ignitions require twelve volts. My Vincent was still six volts, and for some reason unknown to me, a voice in my head was actively discouraging me from converting to twelve. As magnetos require no electrical input, I really wanted to stay with a magneto if possible.

One night after searching the Internet for information on magnetos, I found BT-H MAGNETOS.  I read their information and sent them an e-mail with questions. Their response was prompt and detailed. The prospect of replacing my 53-year-old Lucas magneto with a magneto of current technology, material and design was very appealing, and I very quickly decided to give it a shot and purchased one of their magnetos.

I e-mailed Tony and sent payment. He responded, asking if I would be running the stock ATD and if I needed the unit to fit under my Magneto cowl. I decided to not fit the stock ATD and ordered the parts I needed to make a “fixed” magneto gear from John Healy at Coventry Spares. Six days after my e-mail with Tony at BT-H Magnetos, my magneto arrived with very clear instructions and a hand written note from Tony thanking me for my purchase and letting me know if I had any problems, to contact him.

Below are a series of photographs I took during the installation process that I thought might be helpful to others looking to replace their magneto with one from BT-H Magnetos Ltd.  
(The Vincent owners Spares Scheme do a kit that includes the ET 222/1 drive dog.  Details here.  Webmaster)

  Here are the parts I ordered from John Healy at Coventry Spares for my fixed Magneto gear. They are as follows from left to right:

ET223/1 Steel Pinion Boss.    

E54 Self-Extracting Nut.

ET 48 Fibre Gear/Pinion. (Tufnol)

(4) 617 BA Screws.

(4) 1021 (Lock Washers)

I already had the flat washers.

You may need the following optional parts depending on your installation:

ET 222 Rev-counter drive dog.

ET 224

ET 219

Here is a photo of the magneto as it came from the package. The fit and finish is superior and the quality of build is obvious. The twin coils face forward when mounted to the motor.

The long screwdriver is included in the kit. You need it to fit the lower magneto mounting bolt, inboard, next to the oil filter chamber. You must pull the stud from the case of the motor and replace it with the stainless Allen bolt also included in the kit. The stainless rod shown is used for locking the magneto shaft at the firing position. No more cigarette papers needed. Also the included O-ring eliminates the stock paper magneto gasket. My assembled “fixed” magneto gear and E54 nut are also pictured.

This photo shows the magneto on the bike. The bracket holding the coils needed to be bent to fit under the magneto cowl. Note the stainless rod inserted into the magneto, locking the shaft in place.

Note 1:  When you fit the stainless locking rod  be sure that the shaft is not 180 degrees out.  The correct position is when centre dot on the taper of the shaft is at the top in line with the hole in the magneto body.  There may also be an etched arrow on the end of the shaft pointing up in line with the body hole. (Web Master)

Note2: The mounting bracket supplied is a stainless steel drilled strip.  We have found that most Vincent owners like to put their own stamp on the installation by bending, twisting, or cutting this strip to their own preference. (Web Master)

Here is a little different angle showing the magneto in place on the bike. The coil bracket will have to be unscrewed and the coil assembly dropped down to gain access to the oil filter chamber for filter changes, a very small price to pay. Note the thin black wire that is dropping down out of frame. This wire gets attached to the kill switch on the handlebar.

After finding TDC, the magneto is timed at 35 degrees before TDC. Note the stainless locking rod still in place at the front of the motor. BT-H recommends that the bike be timed with 3-4 degrees less advance for use with modern fuels. I then placed my “fixed” magneto gear on the shaft and tightened the E54 nut to 15 foot pounds, removed the degree wheel and pointer before tightening the magneto down to the case. I removed the stainless rod from the magneto and put the brass inspection plug (not shown) back in the magneto and proceeded to button up the timing side of the motor. Spark Plugs used are NGK BP7ES gapped at .027

A photo of the bike done… It started on the first kick. In all subsequent starts it has taken no more than two kicks, even from dead cold.

In short, I am as happy as if I had good sense. The bike is easier to kick than it has ever been as the magneto automatically retards timing for starting. I have no fear of kickback (I broke my leg badly a year ago so this has become a concern). The internal electronic advance works beautifully and the motor pulls smoothly all the way through the RPM range. I don’t have to use Herculean force to swing the motor around. It just starts…nice and easy.

Although the BT-H unit is not inexpensive, I am firmly convinced that it was well worth every penny. I wish I had found them sooner. I would be happy to share my experience and impressions with anyone interested.

Cheers!

Jess Stockwell

Jstockwell at charter.net (replace "at" with @ and remove spaces.)

Copyright © 2008 E. Grew