GS850 problem: no power and stalls at idle

[maisf]

Hi there!

So I bought this nice 1979 GS850 a week ago.

Got a few issues with the battery and the petcock but figure them out by last friday.

I finally could ride the bike last friday and got her running nice and smooth.
I went sailing around the house for 40 km. Everything was great, lot of power all over the RPM, it was great at idling and all.

I was back, just half a km away when I had a big drop in power, very sluggish throttle response. Motor would just died if dropped below 2000 rpm. I was like WTF!!!

Did manage to get back home, barely...

Now... well I first thought it was some crap from the gas tank that got stocked in the petcock as the filter / strainer was just gone.
I have ordered a new petcock assembly and right now I'm running on "PRI" position on the old one so it's on reserve and bypassing the damaged diaphragm thing.
But when I removed the gas tank and got the petcock in the "PRI" position, gas was flowing right through...
And since I added an inline gas filter, I think gas isn't a problem as of now.

So I'm a bit lost now... I know I had charging problems (connections) so could this be related?
I know coils could use some love, what are the symptoms of having a few cylinders not firing up?

The bike has an electronic ignition thing, the online help I found were talking about points.

Any troubleshooting advices are welcome!

Here's what my ignition looks like:

GS850 ignitor.jpg

Thanks!

[Big T]

Never heard of Per Lux, I looked it up and I see that they are big in vintage auto.

So, start with pulling all 4 spark plugs and see if they're all firing

[maisf]

Never heard of Per Lux, I looked it up and I see that they are big in vintage auto.

So, start with pulling all 4 spark plugs and see if they're all firing

Yeah, I'll test these later... I did pulled out the gas tank quite a few times in the past week so I guess I may have disturbed a few connections in there.

Thanks!

Frank

[maisf]

Hi there,

So I tested the spark plugs yesterday and they won't fire on cylinders 1 and 4.
I did tried a few measurements but I got overwhelmed a bit by the mess of all these cables.

I have the Bike Cliff diagnose sheet but I'm afraid it'll only help after some explanations...

1- Test the coils themselves: Am I supposed to be able to measure something between the 2 spark plugs cables? I have an open circuit... Cliff is talking about 130-200 Ohms or 3-5 Ohms. Then he's talking about a pickup... What's that?
2- The oranges wires (positive feed) to the coils have quite a drop to them, from 12,6 volts at the battery to below 10 volts at the coils. Where's that drop coming from???
- Is it possible to have that much loss through kill switch and the key switch? I mean shouldn't this be an on and off thing?
3- If I understand right what is coming out of the ignition is a ground?

Thanks!

Frank

[Brendan W]

Hi there,

So I tested the spark plugs yesterday and they won't fire on cylinders 1 and 4.
I did tried a few measurements but I got overwhelmed a bit by the mess of all these cables.

I have the Bike Cliff diagnose sheet but I'm afraid it'll only help after some explanations...

1- Test the coils themselves: Am I supposed to be able to measure something between the 2 spark plugs cables? I have an open circuit... Cliff is talking about 130-200 Ohms or 3-5 Ohms. Then he's talking about a pickup... What's t
2- The oranges wires (positive feed) to the coils have quite a drop to them, from 12,6 volts at the battery to below 10 volts at the coils. Where's that drop coming from???
- Is it possible to have that much loss through kill switch and the key switch? I mean schould this be an on and off thing?
3- If I understand right what is coming out of the ignition is a ground?

Thanks!

Frank

Yes, and another usual suspect is the coil supply plug itself hiding corrosion.
Cleaning my ign, kill, fusebox and it's plug gave me back almost a full Volt and cured lazy starting and misfiring.
I lost two cylinders on the road one day. It was the coil plug.

[maisf]

Ok, it looks like I'm moving forward a bit now...
The fusebox looks new, so I guess the previous owner swap it out.
I cleanned up the main connector right after the fusebox.
I cleanned up the primary connectors of both coils.

The coils are looking fine, I got 4 Ohms on the primary and 32kOhms on the secondary, I guess that's good.

Battery at rest is at 12,6 volts, ignition on drops at 12,3
I'm putting her on the charger a bit.

I'm having a 1 volt drop at the ignition switch and another 0,6 volt at the kill switch.
You guys thinks it's just a matter of cleaning out contacts right?

I saw a thread about putting a relay directly between plus of the battery and the primary plus of the coils...
Maybe I can just put a switch on/off?

If I run a direct cable in there, is this a test I can do to see if the spark plug will light up?

[maisf]

Lastest update:

I've cleaned all connections in the headlamp and found a few bad ones in there. One four-cables connection almost turned into dust in my hands... lol
Right now I'm having a 0.3 Volts drop across the ignition switch instead of 1 volt.

But... still no fire... gosh...

I tried bypassing everything and getting the battery plus directly on the primary coil but nothing good happened.
After thinking about it, I tested if the coil that was ok still is, so I know for sure I haven't mess something up while cleanning everything. Spark is ok on cyl 2 and 3 so nothing f*cked up.

So I'm beginning to see the electronic igniter as a possible culprit.

I got no idea on how to test this thing...
Haven't got a clue from a few searches either in the Bike Cliff papers or in the GSR forum, as far as I can tell...

Any electronic ignition expert in here?

Thanks guys!

[Big T]

If you're talking about the Per Lux ignition pick ups that you posted a picture of, yes, that could be your problem

But, you're bike does not have an ignitor. That's a later, stock Suzuki part

If the Per Lux pick up has failed, you can buy a Dyna S electronic ignition for your bike. I think the fact that I've never heard of/seen a Per Lux and my 38 year old Dyna is still working may be a clue

[Grimly]

^^^^^^^^ Wot he sed.
I've seen ads for the PerLux Ignitor but never run into one - different areas of the world had aftermarket makers of their own points-replacement systems. The most common for GSs over here was Piranha / Lumenition / etc. All doing the same thing and essentially pretty much the same design.
The modern Dyna system seems to be pretty good, with very few failures (not that it doesn't happen, but it's pretty rare) and they've taken it a stage further with the triggers and ignitor units consolidated into two small items that basically replace your existing triggers (well, what used to be points).
I've been running Piranha systems for decades with no trouble at all, but I don't expect them to last forever, and when mine eventually go down, I'll have a serious look at Dyna units. I'd have had one before but the retail cost over here put me off; they're much cheaper where you are.

[maisf]

Hi there again!

Ok I did finally figured how to test that godam electronic thingy (ignition pickups?). Honestly, I was pretty confident it was working, as it didn't look very beated up.

BikeCliff's pages are very informative, combined with the right manual shop for my bike, I found all the info I needed.

So I 've figured out that by turning the crank I'm supposed to have electrical movement (ground to 12 volts and vice versa) on both output of the pickups.
My not-sparking coil had the white cable going in this and the coil with the black cable was firing ok.

Well guess what, nothing moving on the white side, black side was moving good.
Final test, I plugged the black cable (the good one) in the white that's going in the not working coil.
Spark!

Good lord thank you, at last that thing is firing!

A few searches pointed me to a Dyna-S replacement.
There was some notes about knowing if I had a Nippon-Denso or Kokusan model points... WTF... My bike doesn't have the originals in there...

As usual, the solution was in BikeCliff's pages, a pdf showed the differences between the 2 and according to the service manual of my bike, I had the Nippon Denso as OEM.

So I did gunned down on a Dyna-S on a reputable web site. Not cheap, gulp...

And fingers crossed, that'll be the end of that ignition problem of mine.

I'll keep you posted when the Dyna gets in...

Thanks for hearing me.

Frank

[maisf]

Eh dudes!

I've got the Dyna-S coming in yesterday.
Installation intructions took a bit of time to figured out, but I got moving on after a few check with BikeCliff's pages and the shop manual, as usual.

She's back to life!

I went for a ride afterwards for quite a few kilometers and all is good!
Just a few backfires when downshifting, I'll move the advance plate a bit to see if it cures it.

I fell so confident that I filled my first tank.

Hahaha...

Thanks!

[bwringer]

I just love a happy ending!

Seriously, thanks so much for reporting on your journey from beginning to end. That will help someone else one day.


Fortunately, when I had the same problem, it turned out to be only am orange/white wire broken at the connector on the coil. It's important to check everything.