General => Douglas Motorcycles - General Discussion => Topic started by: giz.neal on 10 May 2015 at 18:54

Title: Post war magnetos
Post by: giz.neal on 10 May 2015 at 18:54
Can anyone help with some info regarding magnetos for post war machines. I have been looking at using a 'new' electronic Mag produced by a company in Milton Keynes. The model resembles a K2F in appearance, is self generating and uses 2 small coils to produce a spark (I'm not looking to use lights etc). They can build clockwise or anti-clockwise, so no problem there. I provided a drive pinion from a Mag that I already had but it does not appear to have the same taper as the standard shaft? (used by the new Mag). Is it likely that Douglas had Lucas produce a Mag with an entirely different taper, shaft to pinion? Any info appreciated!!
Title: Re: Post war magnetos
Post by: Neville Heath on 10 May 2015 at 19:55
I cannot think Lucas would have produced a different taper for Douglas bikes. Especially K2F's as that would only have applied to racing Plus models. The numbers involved would never have justified it. Besides what would have been the point.  Some owners used ex stationary engine mags on Pluses. Maybe the taper on the pinnion for those is different and that is what you have. Every Douglas mag I have had anything to do with has had the same taper. K2F mag pinnions for Pluses are the same as for Mag/Dynos for Marks, but those for Plus magdynos have swept forward teeth. Hope this helps a little.
Neville Heath
Title: Re: Post war magnetos
Post by: eddie on 10 May 2015 at 21:14
       The taper on mags fitted to post war Douglases is the standard Lucas taper, but the boss on the mag wheel is usually the full length of the taper (as it goes through the oilseal in the front cover). The taper on modern mags may be a bit shorter, resulting in the wheel sitting against the shoulder before it bites on the taper. As the new mags probably don't rely on a similar oilseal, it may be possible to shorten the boss a little to make the wheel fit.
Title: Re: Post war magnetos
Post by: cardan on 10 May 2015 at 21:49

Of course another option is to use a (real) magneto. Properly reconditioned, a magneto is a most reliable and functional piece of equipment, and in keeping with the age of the bike.


Title: Re: Post war magnetos
Post by: Neville Heath on 11 May 2015 at 21:40
I have a spare 90 Plus mag if you are interested.
I removed it from a plus I run when I fitted lights to it several years ago. It has been stripped and rebuilt but not rewound.
Neville Heath
Title: Re: Post war magnetos
Post by: polly on 12 May 2015 at 14:27
I fitted a new type BTH on a velocette for a mate, we had to send it back as one kick was not enough to generate a spark as the gear ratio was to high, use a real one properly rebuilt!
Title: Re: Post war magnetos
Post by: tck on 22 May 2015 at 14:40
I run 3 bikes with BT-H (note the hyphen)  mags never a problem and the 6mm rod to hold the armature in place when timing ,why did not Lucas  or BTH ever think of that? makes a chore a joy.
Title: Re: Post war magnetos
Post by: douglas1947 on 28 May 2015 at 19:26
On my early 90+ (engine no. X90/16) was original fitted a magdyno.
But the crankcase has a different (smaller) hole and also the treaded wholes for changing to a 2Kf mag.
It was necessary to pull off the pinion first to get off the magneto from the crankcase!

The pinion is a 2-piece with a center / taper and - fixed with 2 srews - the outer pinion.

So it is possible to "shim" the pinion to the right lenght!