resistance - should there be some

[wilko]

I think you're running around in circles. Probably nothing to do with the maggy? I'd triple check timing, rag stuck in manifold,gods wrath, time of day etc....

[lawnmowerman]

Bill, I think you have confirmed that both your mags are on the way out - probably only a matter of time when they will not run at the lower compression also.
If the spark is not strong enough it will have problems arcing across the plug gap at higher compression - alternatively it may find a "better" path with less resistance through the mags internals if the insulation is breaking down so not get as far as the plugs.
Couple this with the rubbish we forced to buy as fuel in the UK then any mag problems are intensified.
The problems I had were so similar to yours and in the end I bit the bullet and had the mag rebuilt. It did not run well at first but a new set of N4s cured it and it now rides like a different bike.
Hope you get it sorted soon so you can get some miles in before the winter.

Jim

[bsa-bill]

Jim thanks, you've confirmed what I think is going on, I have been thrown my the fact that both Maggies performed the same way.
Also ordinary plugs (N3,4,5, B6,7) wont spark in the pot and give a weak spark outside but two Bosch plugs I have do give a spark in the pot ( I had it running today) but they are peculiar plugs, very thin electrode like an Iridium plug but apparently silver they are not resistor though , they have an extremely thick metal base, unfortunately they also soot up on a short time (cold plug), no doubt if I sorted out the Bosch code I might find plugs that I could use, not ideal though I should be able to get reliable starting without stocking up a hoard of exotic plugs.

I had a call from old firm yesterday, bit of work to do so I could be flush in a week or so, think I might keep the Maggie as a spare for now and get it looked at when time and dosh allow, meantime I think I might dabble in the Pazon direction, a plan is hatching - involves two batteries and some sort of switching arrangement to allow use and charge of either, thereby always having a fully charged battery on board.

Could be I'm a glutton for punishment

Thanks all once again for the help

[muskrat]

G'day Bill,
             if your going down that path why not go for a dvr2 reg to convert the 6v generated by the dyno to 12v for the ign and lights, running 1 12v bat.
Works well on both of mine.
Cheers.

[bsa-bill]

Hi Musky
I have a v-reg 6/12 volt reg from http://www.norbsa02.freeuk.com/index.htm and had the dynamo upgraded to 12 volt and run a 12 volt battery, batteries are a lot smaller these days so two slim ones should fit in the space, some sort of mechanical switch-over would give an option ( to be sure to be sure)
So I'm looking at the Pazon Sure fire as it works down to 8 volts and has a 7 1/2 year warranty, apparently made by former management at Boyer ?
Looked at the Wassel one too, looks sound as it's encased in silicon but it only comes with one year warranty,  would have thought these days they should have enough faith in it to give a bit more than that.

Also have been looking at Bosch plugs, I'm impressed with the ones I have got ( the only ones that will start the bike it seems, that fact alone sort of points to the maggie as the weak spot)
Found some that are N4/N5 and such compatible and with the silver thin wire centre electrode also non resistor, got a couple ordered.
Found them on this site http://www.boschsparkplugs.net/411.asp?pt=1. lot of interesting stuff in the "plug problem" section, kind of explains why plugs go dead and for me gives some reason as to why every indication of the plug sparking but no fire - interesting reading.

Been at work for the last week so just getting down to some maggie detective work this afternoon (in between British Super Bike and Moto GP)

Yep I'm thinking along the lines of trying the electronics and keep he maggie for a spare, then sell it in five years or so as a rare RGS component ( five years on I might have this bike going) 

[chaterlea25]

Hi Bill and All,
Have a read of this article on plug fouling
http://www.gsparkplug.com/shop/fouling-shortingout-problem-modern-plugs-champion-vs-ngk/

I had a set of NGK's give me trouble during the week, The bike was running and starting fine
After refuelling is started to miss and became harder and harder to start 
I blamed the petrol ?? but when I went and refilled the next day the problem persisted ????
A new set of plugs and problem dissapeared

I was on the Irish National Rally so 500 odd miles during the week 

Regards
John O R

[bsa-bill]

I've read that one John, certainly fits in with a lot complaints about plugs.

I'm also thinking there is something in the theory that that common plug types are not quality controlled at all (sorry forget who stated this) which might explain why the more exotic type work better, perhaps they are tested

[bsa-bill]

Got around to doing a comparative test between my two Maggies, (trying to stop running around in circles  , none taken Wilko)
Checked out the meter leads and battery just to be sure

Centre screw removed - points open   - resistance in ohms
                                                                               Mag 1                           mag2
fixed contact point to mag body                                   7.4                               69.5
moving contact point to mag body                               open                             open
moving point brass pivot pin to mag body                     7.3                               69.5

with points closed same tests                                     12.4                             130 - 95   fluctuating

tomorrow I'll nip up the road to Bobs and see what his magnetos read, we did all the ohms, watts, volts , amps stuff a school so I do have a rough idea of it all but that was a long time ago, today I know continuity from an open circuit but beyond that I might as well subscribe to the smoke theory

[trevinoz]

Bill,
           I have just measured the resistances of a newly rewound armature and I get -
           High tension - 5200 ohms
           Low  tension - 0.5 ohm
This is without points or slipring fitted.

  Trev.
 

[bsa-bill]

Hi Trev
Many thanks
Tested  mate Bob,s spare maggie yesterday and got same result as Mag B so I've got an odd man out, which just happens to be the one on the RGF.
Will take it off today and copy your test and see what I get, also a look inside will see what condition it's in and anything obvious, should contain a nice clean newish looking rewound armature   

Will decide today which way to go,probably will try Pazon , will then have a spare maggie but as Bob remarked about his spare Maggie "it's probably doing better than money in the bank these days)

[bsa-bill]

dismantled the Magneto today, slight problem with the safety screws, both were extremely tight and a fair bit of corrosion on them, the head broke off one of them so not ideal, had to break off the bottom of it to get the armature out.
I can get the 0.5 ohm reading but the high tension ( testing from the brass on the slip ring to the taper on the drive shaft ) is erratic, I get 1500 to 800 and many in between but they just flash up on the meter and then disappear.
Also pretty black grease in the bearings and are they meant to be slackish?

any way a Pazon surefire ordered along with a billet housing, I'll sort the Magneto at my pleasure

[chaterlea25]

Hi Bill,
You need to check from the high tension slipring to the centre bolt that holds in the points (points rotor removed)
The inner end of the high tension winding is connected to the low tension winding so unless the mag is complete and the points closed there will be weird readings??
quite often if using a digital meter the HT winding will show open circuit
this is because the connection is only pushed into the slip ring and not soldered or crimped

HTH
John O R

[bsa-bill]

Ah thanks John, will do that tomorrow although I think I've already done it.
Have ordered a Surefire from Mr Goff and will build up the Magneto with new bearings and seals as a spare
I'll get a photo of the armature and what I presume is the capacitor (or two) encapsulated in the end of the armature, they look a bit old fashioned  what else could they be though?
Armature looks like it's been dragged past a safety screw at some time , big deep scratch along it's length (wasn't me honest).

Many thanks once more to all who have chipped in on this saga

[lawnmowerman]

Had my mag rebuilt recently and two capacitors were fitted opposite each other supposedly to improve the armature balancing  - I think only one was fitted originally.
I had erratic readings too on the mag pre rebuild and John O R mentioned at the time that the HT winding is only pushed under the slip ring so I put it down to that. It seemed that I got various readings on different parts of the ring and at differents pressures on the probe.
If only Joe Lucas had made guns we would never have had any wars 

Jim

[bsa-bill]

Hi Jim
I think I have two capacitors fitted also, are these encapsulated into the end of the armature, they don't look too modern to my eyes
and they are different in detail although they could be facing different ways.(the capacitor not my eyes)
Writing on them is as follows

           on first one                                     on the next
               RIFA                                             275 V~ SH
          pme271M                                        14 RJ   ( Csa )this looks like a trade mark         
              5v9                                                 250 VAC           
         40/110/56/B                                                   
       
     
Found the manual for my meter so got the "resolution" for the ranges
take your point about the variable readings.

so I get 0.5 ohms Lt      4.32Kohms HT  seems low compared to what you guys are getting, armature windings shorted somewhere?

Certainly has been out before as big scratch would testify, also evidence of wires soldered to edge of armature on both sides?