Magneto magnet strength

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Tigercub
Posts: 16
Joined: Fri Sep 29, 2017 11:17 pm
Location: Warwickshire England

Re: Magneto magnet strength

Post by Tigercub »

I can be dippy....rule is part stainless..tried again with a drill, alot better, but I think still not great..
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Magneto magnet strength

Post by Rob Harknett »

Tigercub wrote:I bought 4 brand new plugs, i'm a 2 stroke nut, plugs are the bain of my life. I agree, once they've been 'oiled' these days then cleaning them seems to be a waste of time. Something in modern petrol seems to destroy them. I've just had another go with a steel rule on my magnets...hopeless... one is better than the other but both seem very weak. Any way it's getting boxed up now and sent to Bill in France...see what he says.
It is not something in petrol that destroys plugs, cleaning destroys them. Since 1970's pugs have not had the central electrode glazed. Cleaning actually damages the unglazed electrode causing the plug to quickly contaminate. So when in the engine the plug will give many weak sparks and the engine not start. If you did not try a new plug, you may have wasted your time and money on the mag.
Tigercub
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Joined: Fri Sep 29, 2017 11:17 pm
Location: Warwickshire England

Re: Magneto magnet strength

Post by Tigercub »

It's had numerous new plugs. Funnily enough the plugs that come out of it go in something else and work perfectly. Im convinced it's the mag, wether condenser, magnetism, or coils.... I'll find out.
I've spent ages on carburetion to get that right. It has a monobloc cos the body on the original cracked. The other thing about this is, sometimes it will start warm, and when it does it will do again and again. Next time you use it though it decides not to. It all points at the condenser to me, but I'd like to check the rest out whilst it's off and apart.
aobp11
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Location: GLD NETHERLANDS

Re: Magneto magnet strength

Post by aobp11 »

Just for fun. Albert.
Sterktetestje.jpg
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bitza
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Joined: Tue May 27, 2003 1:00 am
Location: SHROPSHIRE UK

Re: Magneto magnet strength

Post by bitza »

Like Rob says could be condenser, I had had similar problem on my g9, fired up ran ok from cold, shut her off when hot, then got you
Kicking it over like a numpty, took it to Tony Cooper , straight off said it's the condenser ,mag rebuilt with new bearings etc. job
Guaranteed. Refitted bike starts first time everytime
Tigercub
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Joined: Fri Sep 29, 2017 11:17 pm
Location: Warwickshire England

Re: Magneto magnet strength

Post by Tigercub »

That picture tells me all I wanted to know... excellent..
56G80S
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Location: N YORKS UK

Re: Magneto magnet strength

Post by 56G80S »

Easycap is brilliant in my SR1, but then Tony C had previously rebuilt it. Traditional condensor failed in relatively short order - nothing to do with Tony who did a great job. Of course, no actual need to delve into the guts of the mag.

I find that using meths and a toothbrush can get the sooty plug going again but not if it's already been attacked with a brass brush - or perhaps I'm lucky. I have found that the new monobloc (from Kettering) has made a real difference to starting, idling and low speed response. I am having a problem with sooting up but that's partly I think because of small throttle opening running since rebuild and very slow speed when getting to lock up. When I killed the engine and piulled over and checked during a run it was fine; running on the stand (you referred to this earlier) can have the same effect?

Anyhow, gone to Bill now and sure he'll sort it.

Johnny B
Tigercub
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Joined: Fri Sep 29, 2017 11:17 pm
Location: Warwickshire England

Re: Magneto magnet strength

Post by Tigercub »

In same area...I have another question. Packed inside the mag chain drive cover was what must of been a whole tub of orange coloured grease. Is this what's supposed to be in there. There was a hell of alot of the stuff.
Tigercub
Posts: 16
Joined: Fri Sep 29, 2017 11:17 pm
Location: Warwickshire England

Re: Magneto magnet strength

Post by Tigercub »

Right, I've done the condensectomy as per the excellent instructions on Brightspark site. Just wait now for body to come back from France and easycap to come in the post. That should most definitely eliminate the mag. I bought a set of rings a while back but can't decide wether it needs them. Bike has done a genuine 40,000 miles from new but doesn't smoke or anything and goes really well.busting a gut now to test this mag. Inside, the mag looked original, like it hadn't been touched since 1952...amazing.
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Group Leader
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Joined: Tue Nov 29, 2005 8:51 pm
Location: Herts UK

Re: Magneto magnet strength

Post by Group Leader »

Andy 51 wrote: Hi, My 18S and G80 (both '54, SR1 mag) have the same issue - great starting cold or hot, not so good warm. I find they start OK when warm if well flooded. Sorry to sound if I'm teaching grandmother to suck eggs, have you tried flooding the engine (tricky to differentiate between flooding and drenching, I know)? The carb could be at fault too, I fitted a replacement new carb this spring and it makes starting much easier. Andy
I've found my 16MS to be tricky to start when warm or hot and a friend mentioned the old "reduced magnetism when hot" problem.
However, I've found a sudden and marked improvement in such starts as I've become more adventurous with the carb tickler so in my case it appears that, as Andy suggests, it's "Finger trouble".
Tigercub wrote: ..... but doesn't smoke or anything and goes really well.
It it ain't broke, don't fix it ;)

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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