Author Topic: Magneto say Fuel - Spark = Bitch won't start ? Renamed  (Read 1908 times)

Online Triton Thrasher

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #15 on: 30.05. 2017 11:35 »
I would not have much faith in that slip ring, especially in a bike that appears to have magneto trouble.

I believe they must be made from pretty well flawless plastic for long term reliability, or else internal tracking can occur and then get worse as it carbonises plastic and traces of oil in the cracks.


Online Triton Thrasher

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #16 on: 30.05. 2017 11:39 »
Is it possible that the high HT resistance has been caused by it being rewound in a non-standard way?

After all, 18-19 kOhm would be correct on some ignition coils.

Offline duTch

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #17 on: 30.05. 2017 12:20 »

 
Quote
I would not have much faith in that slip ring, especially in a bike that appears to have magneto trouble.

I believe they must be made from pretty well flawless plastic for long term reliability, or else internal tracking can occur and then get worse as it carbonises plastic and traces of oil in the cracks.

 I looks better than it did at first... *eek*

 
Quote
Is it possible that the high HT resistance has been caused by it being rewound in a non-standard way?

 It did cross my mind, but no idea of its functionality or otherwise- way outta my league. I'll see if Les is still around, and can enlighten me.

 Slip-ring has worked fine for four years  *dunno*, I'm thinking to rustle up a whole replacement spare maggie for emergencies like now


Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline chaterlea25

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #18 on: 30.05. 2017 12:32 »
Hi All,
The pic of the slipring looks all to familiar *sad2*
Well and truly Fkd!!

Test resistance from one plug lead to the other, if theres any reading other than infinity on a low voltage meter = dead
I use a 500v Megger to test the sliprings, that will soon show any problems
There have been a lot of crap sliprings on the market, I had two fail on the A10 before I modified a proper BTH mag to fit

John
1961 Super Rocket
1963 RGS (ongoing)

Online JulianS

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #19 on: 30.05. 2017 12:37 »
Maybe not the cause of the failure, but for future reliability I would do a bit to the contact breaker assembly - replace the spring which retains the moving contact in position, move the little backing spring to the post side of the main spring and replace the card with a suitable diameter hard fibre washer.

Online Triton Thrasher

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #20 on: 30.05. 2017 13:00 »
As Julian says, where is your moving point retaining arm?


Online groily

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #21 on: 30.05. 2017 13:34 »
Busted off TT by the looks of it. I wonder if there is a lot of slop on the pivot post too - it's another job worth sorting if the thing is coming to bits anyway, although a fiddly one. The problem is that wear there causes poor opening, promotes arcing at the points and very often upsets the firing interval between the two sparks by several degrees.
The buffer spring needs sorting, the fixed point is 'unusual' in having had its hex turned into a knurl(!) and it really should have its retaining clip and little titty thing to help keep things straight. The clips can often be had - or in the worst case a bit of junior hacksaw blade cut & ground to suit, punched through  to make an 'ole and clouted carefully to make a register for the tit does a neat job that's almost indistinguishable from the original (with a bit of patience!). The pin may also be available, or a small (6 or so BA) screw and shallow nut can serve if the pinhole is tapped, although it may be tight if there is an (optional) auxiliary earth brush meeting things from the other direction.

As to winding recipes and TT's query above  . . . very occasionally I have seen (rotating) mag coils wound to produce a simple HT resistance as high as  8000 ohms, but never anything like 19K. But I agree there are car-type coils which show much higher figures, certainly, and static coils are quite often close to 5 figures on some magnetos. 'Normal', if there is such a thing, seems to be from 4500 to maybe 6000 ohms depending on who's done it. Commonly, 5000, near enough spot-on. Some of the competition windings seem to have had a bit more wire on back in the day judging from from some of the readings, but AFAIK the majority of winders treat all K series coils pretty much the same these days.

The slipring isn't worth persevering with. It probably leaks, will almost certainly be prone to tracking and so on, and its surface is  rough enough to eat brushes I'd guess. I wouldn't be at all surprised if connectivity inside was poor and responsible for the poor HT reading, but the only way to find out is to get it off and measure from the bare spike of the coil.

I think the mag needs a fresh going over to be honest, to eliminate the risk factors one by one and get it back to full health!
Bill

Offline RichardL

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #22 on: 30.05. 2017 15:25 »
I'm still a little hung up on the fact that the night before the problem started, Dutch left the pub, gave it a couple of kicks, and got home with no apparent issues. Sometimes lurking problems turn on like a switch, but it seems to me that this slip-ring thing would show up progrescsively, if it's indeed the problem. This said, it does seem that this might be one of those times when the problem, whatever it turns out to be, turned on like a switch.

Oops, edited: I am interpreting Groily to mean that leaks lead to the crazing on the surface of the slip ring, so I went looking for images to show other cases. I came accross this video from Brightspark Magnetos (Groily, you may have heard of them): https://m.youtube.com/watch?v=Jeq1h9dOoKo . So, assuming leaks are the issue, did they just want one more trip to the pub before passing out?

Richard L.
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Online groily

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #23 on: 30.05. 2017 16:58 »
Ha! Hadn't seen that one for ages Richard. But I do remember we had fun doing the mods to make the bits and then watching the effects. Good of you to dig it up!

But like you, I'm not sure about the 'switch' thing either. There are several things that aren't exactly optimal with the offending instrument, so it could be a combination, or maybe just one thing that has been holding up, just, but now got to the point of being obstinate. Everything works until it doesn't, and the reason for 'doesn't' won't always or necessarily be a breakage as such, especially where the thing does still work, at least some of the time and/or badly. Basically, I dunno! But I'd still go for an overhaul even if it comes back to life  for peace of mind.
Bill

Offline duTch

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #24 on: 30.05. 2017 23:10 »

  Thanks guys, but first some credits;

 
Quote
As Julian says, where is your moving point retaining arm?

 I think it's in a box somewhere- jumped ship about four years ago, and I keep forgetting about it, but seems they hard to find... but groily's idea sounds sound, and thinking different ideas to fabricate a 'Pip' (moulding one with a two pack?)

 
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........left the pub, gave it a couple of kicks, .......
*eek*  how about just one   *smile*

 
Quote
...The buffer spring needs sorting, the fixed point is 'unusual' in having had its hex turned into a knurl(!)...

 If the 'Buffer spring' is he one Julian mentioned, I was looking at that wondering that it didn't look right- probably from when I took the moving points of to dab some grease on the pivot a while ago....The knurled fixed point is not mine, but in TT's pic.

 John;
Quote
Test resistance from one plug lead to the other, if theres any reading other than infinity on a low voltage meter = dead
I use a 500v Megger to test the sliprings, that will soon show any problems

  At first I thought 'Megger' you meant a 'Growler' for testing armatures- so what's a Megger?

 I tested right through from one plug tip to the other and turned the engine slowly, to have a reading of  '1' (where I presume 1 = infinity?) removed the leads at the pickups, and same result and at the same time rechecked the resistance to the centre bolt and today have a read of 14.6 KΩ both sides (through the pickups, which didn't affect the values yesterday compared to straight to slip-ring)
 
 So thanks guys, I guess I'll be doing today what I wasn't planning to do......maybe



Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline RichardL

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #25 on: 30.05. 2017 23:24 »
Quote
So thanks guys, I guess I'll be doing today what I wasn't planning to do......maybe

Of course you mean taking the wife to dinner and a movie.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline chaterlea25

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #26 on: 30.05. 2017 23:28 »
Hi Dutch,
Megger is a name  (like Hoover) of a brand of insulation tester,
I suppose Megger were the original of the species,
Its an instrument that applies a high(250,500,1000v or higher) DC test voltage to a piece of equipment to test the "quality" of the insulation

https://uk.megger.com/products/insulation-testing

Any sparkie worth the name will have one *ex*

John

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1963 RGS (ongoing)

Offline RichardL

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #27 on: 30.05. 2017 23:36 »
My dad, who was an electrician on submarines in the '20s, had a Megger for testing motors in his (later) electrical contracting business. Wish I had had the awareness to claim it before he closed shop in the late '80s.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline coater87

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #28 on: 31.05. 2017 11:22 »
 Dutch,

 Is it my computer or does the slip ring look pretty bad? Almost like the copper pad is breaking apart or something.

 Lee

 
Central Wisconsin in the U.S.

Offline duTch

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Re: Magneto say Fuel - Spark = Bitch won't start ? Renamed
« Reply #29 on: 31.05. 2017 23:16 »

 
Quote
Of course you mean taking the wife to dinner and a movie.

 I don't have one of them, and generally do those thing if and when I want (or need), but I could possibly borrow one if I needed the interference *smile*

Quote
Its an instrument that applies a high(250,500,1000v or higher) DC test voltage to a piece of equipment to test the "quality" of the insulation

 Ok thanks ....obviously I don't have one or similar and I haven't found that function on any of my multi-meters.. *conf*

  So yesterday I didn't achieve much other than in the process of tracking down Les McKitterick (magneto rebuilder- so I could ask about extra resistance/technique) , I discovered that he's no longer with us, but a guy who worked with him for his last two years has apparently bought all his stuff and now doing the work.
 I have his number so will call him later and if anyone in Brizzo needs him I'll pass it on (he's in Kallangur).
  Through a search result (Noturn Owners), I also found there's a guy in Adelaide who does K2F rebuilding too.

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Is it my computer or does the slip ring look pretty bad? Almost like the copper pad is breaking apart or something.
  Consensus says it's farqued, but seems odd that would make it play up suddenly and only one side.  *pull hair out*

 ok I've work to do *work*
 
 


Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia