76 Suzuki gt 500 wont shut down

[bultaco59]

Hello everyone, well its like this, im restoring a suzuki gt500 frame up
carbs cleaned jetted for my titan expanion chamber,new topend
new clutch, fired up sounds great, my problem is the key will not kill
the motor nether will the kill sw. I have to use the clutch.
any thoughs?
any help would be great
Please and Thank you
bob in burbank

PS before I started the they both worked fine.

[MCN]

You have the ignition constantly connected somehow.

A petrol/gas engine is normally stopped by disconnecting power to the spark.

(Diesels cut the fuel.)

To prove this, try to start and then disconnect the battery.
It will stop or you will have to call for a Priest.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[bultaco59]

hello the motor doesnt use the battery spark,it s running with battery
disconnected ,key off, kill sw in the off position. i was hoping
someone had this happen to them.

[Tankie]

If this machine still has points then it has to have power to generate a spark, recheck your wiring
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Always learning, everyday is a school day

[-]

[Suntan Sid]

During your restoration, have you taken the ignition switch apart and reassembled it?
I had a similar thing on a 70's Yamaha, the previous owner had put the ignition switch back together incorrectly, so what was the "off" position was the "on" position and vice versa!
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"Everybody needs money, that's why they call it money!"

[bikenut]

1976 would probably still have the cb points type ign but you are fitting non standard stuff, so could be anything ?

Ceck against cmsnl for standard stuff.

Dne any painting ??

You have a wiring diagram and had your "suzi" hat on when doing the wring ??
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nuts about bikes

[stinkwheel]

You have an earth problem.

They self-excite.

Both the ignition switch and kill switch make a connection to earth from the low tension side of the ignition coils when in the "off" position. I'd suggest this is not happening. The ignition switch makes and breaks a connection in each position, when it's OFF, it connects the coil to earth and leaves an open circuit for the lighting. When it's ON it connects the lighting to the battery and disconnects the earth.

I used to have a 1971 T500. I can't remember the wiring colours for earthing but if both the ignition and kill switch aren't working, this is where your problem will be. Either a broken earth wire or a rusty/bad connection to the frame earth.

Cutting the power from the battery will do nothing to stop the engine.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Evil Hans]

[WD Forte]

The early CXs used to short the source coil output to ground
to stop the sparks/motor
The ign and kill switches had a common link to the CDI box AC power
to do this
Dont know the bike and havent got the diagram to hand
but perhaps the same method is use here ?
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bikers smell of wee

[bultaco59]

Thats what im talking about, a place to start, thanks for the info.
I will keep you posted.
Bob in Burbank

[MCN]

How the hell is anyone to know CDI or what?

😂


https://www.oldjapanesebikes.com/mraxl_GT_Resource/T500_items/page-A59
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[WD Forte]

[Hong Kong Phooey]

[andym]

Just wanted to butt in about the battery thing, in the past (because I never had jump leads at the time), I've started cars with another cars battery then removed it when running and replaced it with the flat battery.... but I last done this early 2000's, so the technology has probably changed a lot since then.

As for OP, when I first got my '82 GPz project I tried wiring a switch for the ignition (ignition barrel was there but plug that attached was smashed to pieces) I thought just wiring a switch to the thickest wire would have cut the engine.... cue me starting the bike for the first time and the revs jumping up to around 6k, me shitting myself and trying to kill the engine with no luck.... I ended up jamming on both brakes (with the side stand down) and the bike still managed to jolt forward when I kicked it into gear

I realised I'd chose the wrong wire to cut at that point

[Enduro Numpty]

If your GT500 is standard it has CDI ignition - no points. I've got a 1977 version and it stops both with the key or the kill switch.

[MCN]

[Mike916sp]

Just a point as a Gt500 owner.

The GT has CDI ignition the T500 as standard had points.

A GT will though start and run without a battery connected.

Not certain why not stopping though though it's obviously an ignition issue
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2007 Ducati 1098s Tricolore, 1994 Ducati 916s1, 1990 Kawasaki 250 Kr1s, 1976 Suzuki GT500 and Honda Lawnmower with hydrostatic drive. Forever an optimist it can be fixed!!!

[RhynoCZ]

[Teflon-Mike]

You don't even need a battery to 'wake-up' a magneto ignition. You might if you have a car with an alternator, that has windings spinning inside windings, so the elecic is made from one electro magnet cutting the field of another electro-magnet, so you need electric to make the magnet to get it started.

On a magneto system, you have permenent magnets on the rotor on the end of the crank, wizzing past windings on the stator, when the engine turns, that make electric from magnet passing coil.. and they'll do it regardless of whether there is any electric in the system to start with.

Back to top... as suggested, the usual way of killing a motorbike or lawn mower engine isn't to turn 'off' the supply of electric going to the coil making the spark.. whether that comes from a battery, a black box, or direct from a magneto winding..... but, 'short circuit' the coil, so that what electric is sent to the spark-making coil, by-passes the coil, doesn'ty make a spark, and the engine stops running, and the magnets stop passing the winding to make any more spark making electric.

Engine not switching off on either the key, or the kill switcch, would imply that the circuit that by-passed and earths the coil, isn't being made by either.. so corroded contact, missing contact, broken wire, some where between switch and the magneto-earth.

Check that there's good earths in the rats nest of wiring in the headlamp, and that therer is a good and propper earth strap between the headlamp rats-nest and the frame, and or engine.

Not unheard off, for everything to get coupled up in the headlamp shell, and on an old bike, the headlamp shell or its mounts to be replaced with plastic, so there is no metal return path from the common earth node in the lamp, back through the forks and head-stock, back to the engine. Other equipment, like lamps or horn, will 'find' an earth path through other devices on the same circuit earthed frame-side.. indicators for example often use an earth bridge made by the tell-tale lamp in the speedo, so the 'on' side' indicator finds its earth return through the 'off' side one, or the tail-lamp finds its earth through the stop-lamp, and all the other equipment 'seems' to work, if not particularly well, and the engine runs.... it just dont srop!

Hence look for bad earth points.

As said, good-form, even if not fitted as standard, is to add a seperate earth wire between the magneto back-plate and the frame, to give an earth route that doesn't go through an engine bolt, which especially on restorations, can get insulated by new paint or plastic-coating.

Ditto between the headlamp shell, and the frame; the earth path back from the lamp, is likely trying to find its way through the head-stock steering bearings and grease, and again, can be insulated by modern taper-rollers, and or paint or powder-coatings, and earthing high current through a ball-bearing isn't particularly wonderful to start with..... And if there 'was' a comon earth wire between the frame and the head-lamp as standard.. that is often old by now, and cracked, and as it was flexed every time the handle-bars were turned, likely to frey, or break and not provide a circuit in antiquity.....

MEANWHILE.... chasing spagetti can be rather frustrating..... simple 'fix' is to use a spade and slider male+female 'Lucar' connection on the ignition coil connection, to give a second wire coming off it... take the new wire to earth to kill sparks.... either by touching bare wire to a known good frame earth, or via a switch, you cam mount at your convenience, to do the same job as the OE 'kill' circuit.... Old 'paddock'; trick done to road bikes converted for trials or road-race or other wise stripped of standard electrikery and probably a barrel key ignition switch, to save having to stall through the clutch or risk a jolt taking the spark-plug cap off!!

Also worth mentioning to UK BCFers, chap calls himself "Bob in Burbank" burbank is in California USA (or at least famouse one is!). US often got different 'variants' of models to europe, and or model names, anomolies twixt GT500 and T500 could be accounted for by that, and of fact that actual model-years may be anomolouse, because of teh difference between year of manufacture and year of sale, and potential for bikes to have been sitting in warehouses or obscure hick-town dealers for moths or even years between being imported and sold/used, and possibly not even registered for road-use... before the myriad of posible confusions created by a an old bike loosing its providence over the decades, being hacked and bashed to work painted and modded by however many owners with available parts that could come from anywhere from a GMC truck to an old grain silo fan, as easily as a Suzuki dealer or any other brand of motorcycle, depending how far the bodger is located from civilisation!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Teflon-Mike]

Actually... post-script to topic, and Bob-in-Burbank, might be able to put me out of my mental anguish.... B-U-T I recall from my yoof, a 'joke' amongst mid-west hot-rodders, a bit like the jest about pink and black power-bands here in the UK, whyen folk asked if a Z28 or whatever had had, I 'think' it was something like the 'Miller-Ignition-Upgrade'... which had a seed of truth behind it....

The mod, and I cant recall whether it was on Mopar, Chevvy or Ford motors, but back in the 50's when tuned they suffered terrible 'points-bounce' when tuned to higher rpms, than the steam-ship crank speeds they turned from the factory... the impromptu 'Fix' at the drag strip, was to make the points spring heavier with another strip of metal cut from a beer-can... which were apparently steel in them days.... didn't last long, but heck, thing only had to hold together for ten-seconds! Also gave rise to the retort jest that using a Coors can (or other popular brand of the era) was the 'problem', cos they was aluminium....

Bugging me know, I try remember....
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[stinkwheel]

It'll still kill the engine by earthing the low tension side even if it has a CDI. It'll just do it directly from the CDI instead of the coil.

The problem IS still an earth problem. The ignition swith DOES NOT connect the CDI to the coils when it's on, it connects the coils/CDI to earth when it is off.

Found this:

https://www.ozebook.com/compendium/t500_files/gt500wire.jpg
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.