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Douglas Motorcycles - General Discussion / Re: Magneto capacitor
« Last post by yosemite on Yesterday at 21:51 »
Went out on the bike with an extra condesorbetween the cut out wire and earth as suggested by eddie, did about 20 miles though never went far from home, bike ran fairly well apart from occassional infrequent missfire, didn't stop engine till I got home, then bike restarted easily  so stopped and disconneted extra capacitor and it was impossible to start so resconnected capacitor and bike started easily, so it definatly seems to be capacitorwill leave on for now until I decide what route to go down, either a rebuild or an easy cap condensor, probably the latter. just for cost.
think the mag is a lucas mn2 never paid much attention to it apart from drying points out not long after bI got it andchecking timing.
thanks to all for your help
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Douglas Motorcycles - General Discussion / Re: Magneto capacitor
« Last post by EW-Ron on Yesterday at 20:40 »
is there any reason I cant disconnect it and use an external one permanently? that way if I get further problems it will be easily replaceable.

What sort of magneto do you have ?

The main difficulty of having an external capacitor is that most common British magnetos of the era had a rotating coil,
which means the external connection to the cap has to be through something like the earthing system.
These are often very light duty so performance may be a bit iffy, especially long term.
I think I saw that the BrightSpark website (above) discusses this along the way ?
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Douglas Motorcycles - General Discussion / Re: Magneto capacitor
« Last post by dalgrae on Yesterday at 15:04 »
Hi I have had a Britespark fitted to my mk5 magneto during overhaul ant had no problems at all,the britespark web site video clearly shows how to fit one yourself ,but it was too daunting for me

Colin
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Douglas Motorcycles - General Discussion / Re: Magneto capacitor
« Last post by yosemite on Yesterday at 11:08 »
Think that Iwill try to put an extra in circuit as eddie has suggested, I have a couple of spares for the A65,  if that cures the problem then may  down the brightsapark route.
just had a thought, if the condesor inside the mag is dying is there any reason I cant disconnect it and use an external one permanently? that way if I get further problems it will be easily replaceable.
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Of course you can mention Villiers here Ron. Even Douglas made a Villiers powered machine. The first year of the Douglas Bantam was Villiers powered before they made their own two stroke engine. This is the top Douglas on my shopping list, followed by the EW of course.

Anyway, gudgeon pin end pads. Villiers used a 1/2" solid gudgeon pin with bronze endpads on all their engines for donkeys years. I've never found a pre 1940 engine without them. I don't know when they finally dropped them. All with a little pressure relief hole as Leon says. From memory it is 1/16" but don't hold me to it.

Teflon was used for end pads as well but the only examples I know of were in American competition pistons where life expectancy and usage would be very different from what you are aiming at. Bronze works quite well and is easy to machine, why change?

Cheers, 
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No they don't have to be a tight fit in the pin. Just a spigot to stop them turning sideways!!

Cheers

Leon
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Douglas Motorcycles - General Discussion / Re: End pads for Gudgeon pins
« Last post by Keith on 25 Jan 2020 at 22:35  »
I'm pretty sure that my pins have been made from linear shafting. I did a test drill on the lathe with a center drill pilot hole followed by a 3/16 HSS bit and it all went smoothly. I'm just wondering how deep I should go. The old pads I have seen did not have more than 5mm or so of spigot to go into the pin. Are they supposed to be a tight fit in the pin?

Yep, plastic can be a real pain to remove once its melted onto a surface. There are some modern high temp ones around (think of the 'oven ready' meal containers etc.), and certainly (some) teflon is high-temp rated. But I think I'll stick with the old PB2 bronze as it seems to have worked fine for over century  :D
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Douglas Motorcycles - General Discussion / Re: End pads for Gudgeon pins
« Last post by EW-Ron on 25 Jan 2020 at 21:57  »
That sounds a wee bit like the story of Villiers (are we allowed to mention them here ?) who were experimenting
with some form of plastic big end bearing (nylon ?).

The engine was on test, but came to a bit of a strangled halt.
The technician went to remove the spark plug, but "was startled to see the spark plug snap back almost into position."
Apparently the nylon had migrated a fair way throughout the engine....
Make sure your chosen plastic is sufficiently heatproof. ?

Teflon is probably a good choice.
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Douglas Motorcycles - General Discussion / Re: Magneto capacitor
« Last post by EW-Ron on 25 Jan 2020 at 21:47  »
You only have to remove the armature and snip the connection to the old foil type condensor.

Which often fail, way before the wire needs a rewind.
Although its good insurance to get the whole lot done in one go, its a heck of a lot simpler
(and cheaper ) to just add one of those BrightSpark thingies. ?

Lots of satisfied customers it seems - I must get around to trying one of these dodgy magdynos I have with one.
They start so easy cold that there can't be much wrong with the wire in the windings... ??
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I'm selling this bike on behalf of my father. Registered with the Douglas Club and in original condition, other than the tank which was redone some years ago. Contact me for more details.
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