SR1 mag

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
Liddle
Posts: 10
Joined: Fri Jun 04, 2021 12:30 pm
Location: Lothian UK

SR1 mag

Post by Liddle »

Hi there,I am a newbie here, and need help with a SR1 mag. on a 52 16m engine. It has no spark, I would like to know how to test the unit.It is still on the bike.
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Rob Harknett
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Location: ESSEX UK

Re: SR1 mag

Post by Rob Harknett »

52 should not have an SR1 mag
Liddle
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Joined: Fri Jun 04, 2021 12:30 pm
Location: Lothian UK

Re: SR1 mag

Post by Liddle »

So what are you saying? it will not work?
what should it have? can it be made to work? it looks like its been on engine for years.
engine number starts 52 16ms 1xxx
SPRIDDLER
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Re: SR1 mag

Post by SPRIDDLER »

Welcome to the Forums, Donald.
Don't worry that it's an SR1 as they were fitted as standard to later (1955 and onward models) and it'll work fine on your engine.
It would help if you indicate what checks you have already done (cleaned points and slip ring, checked HT lead and plug cap etc? ).
To save describing all the 'ifs' and 'buts' in checking a mag take a look at the link below which is from the magneto resto business 'Brightspark Magnetos' owned by Jampot member Groily.

http://www.brightsparkmagnetos.com/DIY/index.htm

If it's the condenser playing up there's an Easycap replacement available from Brightspark.
'There is a tide in the affairs of men
Which taken at the flood............'
Groily
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Re: SR1 mag

Post by Groily »

This might help a bit too. There's a troubeshooting page towards the end.
http://www.brightsparkmagnetos.com/libr ... gnetos.pdf
For more detailed stuff, this is also useful, but obviously covers a lot of less relevant ground with the multi-cyl versions and impulse starters etc
http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf

First thing to do is look at points, clean and set gap per booklets above.
Check continuity of HT lead from inside mag cover to plug.
Check that the low tension live wire from the coil, which is usually attached to the mag by an insulated plastic fitting (and may have a wire off for a separate kill button on the 'bars?) isn't shorting to earth. It happens quite often due to deterioration, bad fitting inside or outside the body, etc. That lead is connected at the plastic wotsit - inside - to both the condenser, and the live cb point . . . or should be! A short or break here kills the mag dead.
Also check continuity of HT coil from the solder bobble or brass strip on the coil to the mag body. You want to see several thousnad ohms - anywhere from maybe 5500-7500 at a guess, depending on the exact recipe of the winding. Open Line or Infinity reading is bad, although it may make sparks because the break inside is small enough for the thing to jump and still get to the plug (for now - it's a one way street though).
Condenser also a possibility, definitely - although you'd probably get some sort of spark even if it's duff.
The rotor magnetism is probably OK, even if not 100% as per brand new.
The cam is almost certainly in the right place if the thing ever worked - so shouldn't be a problem nor should it be disturbed (unless clearly mispositioned). It's on a taper. The points should start to open just after the magnetic flip point - literally a very few degrees after - being sure to turn the mag the way it's driven (ACW from the drive end).

Good Luck!
Liddle
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Location: Lothian UK

Re: SR1 mag

Post by Liddle »

Thanks for all the info, I dont know much about magneto's ,but am about to learn, will no doubt have more questions soon!
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clive
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Re: SR1 mag

Post by clive »

It would be helpful to give a bit of history. Is the bike new to you, was it running and has stopped, or has it never run for you etc etc? This will help to make suggestions as to what may be wrong Without being rude if you are new to magnetos are you sure it is an SR1? The timing side magneto chaincase should have a big bulge on it near the top (its where the auto advance retard would be). The SR1 has a black plastic flat cover held in by 3 screws whilst the N1 magneto has a cupped metal cover held on by a spring clip. If the bike has stood many months/years unused the problem may be as simple as oxidisation on the points, just cleaning them with a bit of fine wet and dry may be all that is necessary!
clive
if it ain't broke don't fix
Liddle
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Joined: Fri Jun 04, 2021 12:30 pm
Location: Lothian UK

Re: SR1 mag

Post by Liddle »

Hi there,
Yes the bike is new to me, a barnfind been laid up for umpteen years, I was told it had a SR1mag black front cover 3 screws and plug lead outlet.
followed your advice and now have a spark , condenser test ok points cleaned and gapped , cut ends off ht lead and reconnected. just need a plug cap, my first attempt with a mag.Noticed exhaust tappit tight, and the carburettor will need looking at.
Groily
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Re: SR1 mag

Post by Groily »

Sounds promising so far then.
Others who know all about singles would be able to advise on the steps you really need to take to recommission something that has stood around that long (it'll be a bit of a list methinks), but you may be able to start it when you get there, at least. You'll have to wait and see whether you still have any sparks when it gets good and warm . . . but you could be in luck!
oldsteve
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Re: SR1 mag

Post by oldsteve »

Hi Liddle, I recently bought a 1954 16Ms with an SR1 magneto fitted, the problem I had was that there was no means of advancing or retarding the spark, it had been static timed and it ran but was very flat (no acceleration), does your bike have the auto advance mechanism bump in the timing chain casing?
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