1961 G80CS - New Owner

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Peter Platt
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1961 G80CS - New Owner

Post by Peter Platt »

Hi Folks,

I have recently acquired a 1961 G80CS and am in the process of going around the bike and checking everything. I'm still reading up as well so its a slow process.

On the whole, the bike seems to be very well put together. One thing I've noticed so far is that the final drive (rear) chain seems rather slack. There is about 2 1/4 " of slack with the bike on the centre stand. Is there a good reason for this or should I reduce it and if so to what? I haven't found any specific numbers (for chain slack) for a G80CS yet.

Also, any recommendations on tyre pressures (for road use) would be welcome. The bike is currently fitted with trials style tyres.

Any help is most welcome.

-Pete P.
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saltbox alf
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Re: 1961 G80CS - New Owner

Post by saltbox alf »

Depending on the rear suspension travel on a CS the chain might need more free play, so as not to go tight on full defection, however 2,1/2 in does seem a bit much. If you can get someone to sit, preferable a goodly sized person, on the bike then see how much play you have then.
No idear about pressures, but near max as hopefully written on side of tyre.
Allons-y, amis de Matchless et AJS
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dave16mct
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Re: 1961 G80CS - New Owner

Post by dave16mct »

The books say about 1 1/8" on the stand for touring bikes and about 1/2" off the stand. If you can sit on the bike (off the stand) and get someone to measure it to about 1/2". Better to be a bit slack than too tight. Also always check your primary chain first.
Tyre pressures with knobblies is a personal thing and you may have to experiment. Try 24 front, 28 rear and see what it feels like. Increase/decrease until it feels right.
Cheers Dave
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Peter Platt
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Re: 1961 G80CS - New Owner

Post by Peter Platt »

Thanks folks. I set my M18S to 1 1/8 but was wondering if the CS models need more slack due to longer suspension travel(?).

I will try 24/28psi as a starting point for my tyre pressures.

Thanks again.

-Pete P.
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dave16mct
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Re: 1961 G80CS - New Owner

Post by dave16mct »

I wouldn't have thought the extra suspension travel would make much difference on the road, but don't forget theres a tight spot on most chains, so do your measuring there. Sounds like a great bike, any pics? :)
Dave.
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Peter Platt
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Re: 1961 G80CS - New Owner

Post by Peter Platt »

Thanks for the pointers folks. I have just finished adjusting the chain. I've taken it back to about 1,1/2" (a bit more generous than the recommended 1,1/8) and I'll see how that works out over the next few rides.

By the way, I checked the brake light after doing the chain to make sure it worked OK or if it also needed a tweak after moving the rear wheel back a bit. Result? Nothing. Not a glimmer.

I checked the voltage across the ends of the wires that go into the switch (after popping them out of the switch body) and only got about 1.5 volts. Should I expect to see nearer the full 6 (?) volts across these connectors even without the engine running? The battery seems pretty healthy as it can light up the headlight nice and bright (engine off).

I haven't checked the voltage at the battery yet nor have I taken the brake light cover off to see whats happening inside. I'll do that tomorrow but any pointers in the meantime would be most welcome.

Thanks.

-Pete P.

P.S. I think I checked the brake light when I first checked the bike over a couple of weeks ago and I think it was working then but I can't be sure (senior moment!)

P.P.S I'll post some photos when I get a chance to take some nice ones!
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dave16mct
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Re: 1961 G80CS - New Owner

Post by dave16mct »

Sounds like a wire has got almost worn through, perhaps on the rear tyre? The feed to the brake switch will either be from the battery or the ammeter so check for loose connections there. Try a new wire along side it to see if that works OK.
Dave.
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clive
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Re: 1961 G80CS - New Owner

Post by clive »

sounds like a poor connection within the switch to me. Just had to rebuild one on my G11CS
clive
if it ain't broke don't fix
Don Madden
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Re: 1961 G80CS - New Owner

Post by Don Madden »

As on most AMC bikes, the power to the brake switch connects to the horn, using to hot terminal as a connection, thus both horn & brake switch bypass the ammeter. The ammeter shows no current when the stop lamp is lit, but shows a charge into the battery for a short while after it goes off. I highly recommend converting to 12v electrics which will avoid using the complex "load regulation" of the 6v system which connects the alternator outputs according to lighting requirements. The original alternator was designed to provide power for a coil ignition, which mag fired engines do not require. overcharging the battery on longer trips. A 12v system always regulates the charging system, avoiding this. Sealed batteries should never be connected to an unregulated charging system or the will dry out, sometimes exploding. The 1960-up G80CS/TCS battery is mounted under the air cleaner, requiring it to be removed before the battery can be accessed unless the battery cover is left off or a sealed battery used. A battery is not needed for daylight use but the alternator cannot supply sufficient current to supply headlamp & stop light at the same time, so the head lamp will dim when the brake is applied. I made an aluminum plate that mounts on the two bosses of the seat post, holding the 12v rectifier/regulator & use a sealed AGM battery. Cheers, Don. 8-)
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Peter Platt
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Re: 1961 G80CS - New Owner

Post by Peter Platt »

Thanks for that Don, most helpful.

I spent a bit more time with the bike this evening and with the seat off I can see that the bike has been (very nicely) re-wired and has already been converted to a 12V system. It has a modern reg/rec tucked in behind the battery. I'll check what battery is fitted when I get a mo to whip the air cleaner off (which I hope is a fairly simple job). I would be surprised if it is anything but a modern sealed battery.

I continued with my investigations and discovered a failed stop/tail bulb. Duh. I should have checked that to start with! I tested the brake light switch and it seems to be working as it should.

I just need to figure out what the heck the bulb is so I can get a replacement. I would guess its a common 12V 5/20w stop-tail car type bub but it has no markings on it. Time for some Googling.

Thanks again folks for all your help (and patience).
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