GS550 bad starting

[delwil123]

Hi all, my 1978 GS 550 D has never in the 4 years ive had it been a good starter. This year i wd 40 the ht leads and it was starting quite the thing. That was a week ago, today it would not start, not a hint of starting, not fir
ing nothing. Checking the plugs there was a spark although i would say not good. I had a set of new plugs which i put in, and it started instantly.
I have been buying new plugs every year to get a sure start for MOT as i am never certain it will go.
Someone in the past has fitted electronic ignition and i am not sure how that works or if it has anything to do with it. The old plugs are a little black looking but surely it would still start or fire or something.
Any help would be appreciated.
____________________
mickyboy1

[spottedtango]

Hi there,

Sounds to me like it could be a few things.

I’d check the earths for corrosion on the bike to make sure they aren’t corroded. There will be one on the engine and the frame.

I’d also check the ht coils resistances and where they earth to the frame. Also check leads and spark cap.

How old is the battery?

Also how is the fuelling, have the carbs been cleaned balanced recently? Does it ever flood the engine?

Suzuki’s of this era don’t have the best electrics.I’d take the tank and all that off and go about checking the loom. Especially round the steering head as I’ve seen a few cables wearing through due to movement of the handlebars

[delwil123]

Hi, thanks for quick reply.
will check the coils resistances tomorrow
the battery is only a year old and kept charged all winter
I cleaned the carbs when i first got the bike as it had been sitting for 8 year unused. They have not been balanced. The engine does not get flooded.
I only do about a couple hundred miles on it a year, and it runs perfectly.
Will take the tank off again and check all you suggest.
Oh and i put in Iridium plugs last year and again this time as it seems to start better with them.
Regards
____________________
mickyboy1

[jaffa90]

"""will check the coils resistances tomorrow""

Also as said the leads and caps as well.

New spark plugs will give a better spark more so with Iridium plugs.

Replacing them regular is not the answer.

[delwil123]

Hi again and thanks for your replies
Not getting a reading from one of the coils on the secondry circuit, it flashes a number then blanks, the other coil is reading 24. Both primarys are reading 4.
Looks like i need another coil.
____________________
mickyboy1

[spottedtango]

Primary’s seem fine but when you say 24 is the multimeter set to 1000k so that would be 2400 ohms?

It depends on the multimeter some display 0l , other displays just a 1, some don’t display anything, basically meaning there’s no continuity.

As you’ve said if you aren’t getting a resistance at all one coil it would suggest it needs replaced. 2400ohms is a wee bit low but it is an older coil.

For the age of the bike I’d be tempted to replace both and just keep the one that’s good as a spare. You might find the bike runs better and the other coil isn’t far behind in failing.

[delwil123]

set at 200k and reading 24.4 other coil 1.
thanks for advice I will order 2
____________________
mickyboy1

[delwil123]

Hi again, looking ahead the 2 coils i ordered on ebay are not original and appear to have 2 wires a white and an orange.Due in next couple days The old coils have no + or neg marks, from right coil is a black which goes to pirana ignition box an orange and white which splits one goes to ign box other into the harness. Left coil a white going to ign box and a orange and white to harness, i dont know where they go. Can anyone advise wher the new coloured wires will go.
Also how do i know which HT lead goes to which cylinder, the old leads are numbered. electrics is not my strong point.
many thanks
____________________
mickyboy1

[spottedtango]

I’d take a picture of the old coils before you remove them but if that’s not possible.


The way most 4 cylinders work is the pistons 1 and 4 are usually at top dead centre and pistons 2 and 3 are bottom dead center.


So one coil would do cylinders 1 and 4 (Usually the left one as you sit on the bike) and the other would do 2 and 3 (usually the right)


If you find the bike doesn’t run swap them round

My fathers got an old gs650l that he’s fixing I’ll try and get him to send a pic



As for the wires going into the coil I’m not certain but I don’t think it matters too much

If it doesn’t spark one way switch the wires about and see if you get a spark. It shouldn’t cause any damage as they are low voltage side but as I say if anyone else on the forum know feel free to correct me.

[spottedtango]

Managed to get a pictures of the coils. It would appear negative is black and positive is orange and white.


https://imgur.com/Jy7SDxD.jpg

The other coil I think has been bodged by a previous owner so i don’t think the wiring setup for that one would be much use. I’ll see if there’s a wiring diagram about for it.



Edit: Ok so I managed to find a diagram for it. It pretty much confirms what I’ve said.

https://imgur.com/TKo6tWe.jpg

[delwil123]

Many Many thanks for all your trouble, most impressed. This shows me a lot. Hopefully now when the coils come I can work it all out. Thanks again and stay safe.
Del
____________________
mickyboy1

[delwil123]

Coils arrived today, and I fitted them this morning. They came with no markings and with orange and white wires. I determined that the white wires were the negatives
The bike started first kick all be it with the brand new plugs I fitted earlier, but I am very hopefull this is going to fix the starting problem.
Once again many thanks to the people who spent time helping me out, its always good to get input from others.
Regards to all and keep safe, hopefully this will all blow over soon.
Del
____________________
mickyboy1

[spottedtango]

Good stuff

Now you need to help me figure out why ours isn’t running. Doesn’t seem to want to start.

https://imgur.com/HzjOwHp.jpg


Haha take care mate.