The 'beam' or focal length of the lens needs to be set up by moving the bulb holder 'fore and aft' in its holder in the reflector....To do this the bike has to be parked a set distance from a wall and the rim and reflector removed from the lamp...

Next the clamp screw that holds the bulb is slackened and the bulb is moved either forward or backwards in the holder...

Then hold the rim and reflector against the front of the lam and turn it on...The position to provide the best 'beam' must then be found by experimentation and incremental alterations of the bulb position...

It sounds complicated but isn't...It just requires patience..Without a lens the beam is not as effective as it would be with a later lens, however, with a good reflector a reasonable result is achievable.

Unfortunately from memory I can't recall the optimum distance from the wall that is required...I think it was about 20ft. but I'll try to find the info. to confirm that...

If the reflector is dull (ie not having a bright finish like polished nickel) polish it with some silver polish...The finish of the reflector is critical for a good result...If needed I can get them resilvered at a local plater, contact me off forum if you think that's needed (I'm near Plymouth. S.Devon)...Ian

email (option): ian@wright52.plus.com

Hi Ian done all the adjustments for focusing the bulb in the holder, I used a seperate power supply and adjusted bulb holder off the bike but still beam is useless. The reflector is a new old stock one and is in good order. Just seems the beam is either a spot or a hollow.I am going to try a different type of bulb and see if thats where the problem is....Dave

Hi Dave

Both my M20 and WDCO have halogen lamps, I use an old pre-focus reflector which I cut around the bulb holders to make a holder similar in shape to the Du42 type. They fit perfectly under the original DU42 reflector lamp holder wire retainers. With these you can fit the halogen lamps from Paul Goff (main and pilot). I use the 12V 35w and 10w pilot I recall with a 60W dynamo installed. Any higher on the pilot lamps and you melt the bulb holders. 7AH Yuasa battery in one of Ian's battery boxes works really well, inexpensive and I've had one fitted since prior to Normandy 2014 so seem to last. I'm perfectly happy with the lights for night running considering it is a 70 year old bike. I suppose it could be better without the bathroom glass lens. Email me if you want pictures.

Regards

Rick

email (option): rbrouard@guernsey.net

Sorted just make up stepped reducer ring for H4 bulb just got to sort out pilot bulb, think I will fit a led as a day running light.I didnt use nylon for ring but another type of insulation material which has a higher heat resistance, also made a carb spacer from it for my 32 Enfield sloper...I set the H4 bulb for best focus by leaving it loose so I could move back and forward in the reflector while connected to a 12v supply then measured gap and machined spacer to suit.Best of all I dont have to pay over the top prices for 12v bulbs to suit the old Lucas bulb holder and bulbs are easily available from local garage if you ever want a replacement...Ferg you dont know what your.e missing I like riding at night just got to keep a eye out for deer around here some a big buggers dont want to hit one of those...