Fitting the BT-H Magneto to the Vincent V-Twin.

Please read these instructions all the way through  before starting.   If you do not have sufficient skills or the correct tools have the unit fitted by a recognized Vincent mechanic.

1. Remove your existing ignition system including spark plugs and parts you would normally remove to time your engine.  Try your new BT-H magneto in place before proceeding further.  Some very early post war twins may need some relieving due to the thickness of the early sand castings.  They certainly didn't skimp on materials in this area.  

2. These instructions assume that you are using a fixed timing pinion or that you have permanently locked your auto-advance mechanism so that it cannot operate.  Important.  Remove the lower rear magneto fixing stud from the crankcase.  This is where the supplied Allen head socket screw has to be fitted. 

2. Remove the timing hole screw from the BT-H magneto. 

3. Turn the magneto shaft until the centre punch dot is at the top and the arrow on the end of the shaft points up towards the timing hole.  (Double check this as once the gear and blind fixing nut are fitted in step 9 you will not be able to see the arrow.)

4. Insert the 6mm stainless timing rod into the timing hole. Turn the shaft a little either way to ensure the rod enters fully through the shaft and into the magneto body on the other side.  (If you have lost your 6mm timing rod do not try to use 1/4" round bar.  It is 0.015" too big and will not fit.)

5. Fit  the “O” ring into the machined groove in the flange using a little grease to hold it in place.

6. Put the supplied Allen head socket screw into the lower rear magneto fixing hole.

7. Using the supplied ball end Allen key to keep the screw in place, fit the magneto to the back of the timing case.  N.B.  If you have not removed the timing cover you will not be able to fully tighten the magneto fixings until the timing pinion is secured.

8. Set your engine to required Fully Advanced  ignition point before top dead centre on the rear cylinder using your preferred method.  (Degrees, inches or mm.)  (The electronics automatically retards the ignition for starting.  (See note 1 at the bottom of page.) 

9. Replace the timing pinion and torque the nut to 12-15 ft/lb Maximum and REMOVE THE TIMING ROD. 

10. Fully tighten the three magneto flange fixings.

     End view of H.T. coil.

11. Refit the timing hole screw.

12. Fix the coils under the cowl or other suitable position.  Connect the wiring.
    Wiring. The blue wire goes to the black spade on the H.T. coil, the brown wire goes to the green spade.   The blue wire with a yellow tag goes to the coil with the long (rear cylinder) plug lead.  The coil does not need to be earthed to the frame.   
    The black wire cuts the ignition when earthed.  If you do not use this cut out wire make sure that the end is well insulated so that it can not inadvertently stop the engine.  Check that the connectors to the coils have sufficient clearance when you use the side stands to take out the front wheel.  See photograph

13. Set the spark plug gaps to to 0.018 - 0.020"(0.46 -0.5 mm) and refit.

14. Refit any covers etc and check all fasteners and wiring for security.

15. Start your engine.

Notes.

1. You may find that with modern fuels your engine may perform better using up to 3 – 4 degrees fewer advance than standard.

2. Jess Stockwell's write-up of how he fitted the magneto to his Vincent Twin can be seen here.