Perplexing No Start Saga '79 GS850. Requesting your help!

[DesertRatliff]

Hi all,

I've got a 1979 GS850. Upon purchase, I rebuilt carbs, replaced o-rings, boots, fluids, adjusted valves, etc, etc, etc. I reckon a pretty thorough but standard going over. I set carbs to factory settings. It started up and, with the carbs set there, ran pretty good. I took it for a longer ride (50 miles or so) and, content with its performance, was ready to start on the aesthetic restoration.

As of last fall, it never ran again. It just wouldn't start. I checked valve lash again and replaced spark plugs. I noticed weak spark. I didn't want to fuss with points anyway, so I purchased a Dyna ignition for it and installed it hoping that would be it. Still no start. Weak spark and after several episodes of troubleshooting with Dyna, decided that the ignition was faulty. So sent that in for warranty replacement. With the new ignition installed, still no start. Still pretty weak spark. It doesn't start on starting fluid, but I do get a weak exhaust backfire. Checked and adjusted timing, no change. Changed ignition coils with a spare set I have, still weak spark. Check, double check and re-check Dyna wiring, fuses, factory wiring. Added a new AGM battery as the old one was weak. Still no start, very occasional and weak exhaust backfire, weak spark.

What am I missing? Help!
Thanks!!

 

[tom203]

Take seat off…find the 12v positive feed to ignition coils.. with key “on”measure voltage here before and then
during starter cranking.

 

[DesertRatliff]

Ooh. Good reminder. Forgot to mention, that in all of this, I did the direct-to-battery/relay mod. Just went out and checked voltage with the new battery. 12.5v to the coils before, then ~11v to the coils with the starter cranking.

 

[Gorminrider]

I reckon a pretty thorough but standard going over. I set carbs to factory settings. It started up and, with the carbs set there, ran pretty good. I took it for a longer ride (50 miles or so) and, content with its performance, was ready to start on the aesthetic restoration.
As of last fall, it never ran again. It just wouldn't start.

I hate these threads. WHAT could have changed? Where was it sitting?Your valves didn't just stop working because they sat awhile. More likely, Something You Did Since Last Running or, Old gas,dead battery (nope-done!) Kill switch corroded etc.. down the scale to less likely= Racoon picking lock and pooping in the tank.

 

[rphillips]

Just for kicks, find a NON-resistor plug, any plug that will plug in to your plug cap should work, & check the spark with it, just holding it against the block, like you did with the resistor plug. Probably be the same, but I saw it happen, once...And it'd be a really cheeep, rule that out, test.

 

[DesertRatliff]

I hate these threads. WHAT could have changed? Where was it sitting?Your valves didn't just stop working because they sat awhile. More likely, Something You Did Since Last Running or, Old gas,dead battery (nope-done!) Kill switch corroded etc.. down the scale to less likely= Racoon picking lock and pooping in the tank.

Who doesn't hate these threads, right? Feel free to laugh at my expense and follow along. I feel it's something I've overlooked and the solution posted here may help someone someday.

And for the record, the no-start situation happened overnight, with no molestations of any kind that I recall...in a locked garage with a watch-dog and watch-cat on site the likes of which would scare away all locksmithing varmints of any species. Seriously, this duo has absolutely decimated the rodent population on our 100 acre farm and is moving on to larger prey.

 

[DesertRatliff]

Just for kicks, find a NON-resistor plug, any plug that will plug in to your plug cap should work, & check the spark with it, just holding it against the block, like you did with the resistor plug. Probably be the same, but I saw it happen, once...And it'd be a really cheeep, rule that out, test.

I am up for ALL kicks at this point!! Worth a try.

I've got a whole mess of old spark plugs throughout the various shops on the farm here. How can I identify a non-resistor plug?

 

[rphillips]

Not sure about all brands but usually an R in the number...NGK D8EA-non resistor DR8EA resistor etc

 

[dorkburger]

Speaking of resistor vs non resistor plugs, does that model have resistor caps? I had a resistor cap fail and testing my coils from plug wire to plug wire showed as a bad coil when in reality it was just the cap that was faulty.

Also, the other three caps were loaded with corrosion due to bad cap seals, along with corrosion where the wire connected to the cap.

 

[DesertRatliff]

Whelp, looks like all of my sparkplugs are non-resistor type (on the '79, the '80 and 2 sets of spare in my box).

Also, I trimmed down the spark plug wires on all the coils I had for fresh, non-corroded copper and reattached everything.

What else could I be missing? Does not start on ether and ran fine before it didn't start so have ruled out fuel and compression so reckon it's gotta be spark. I'm pretty sure my static timing is set to at least start. But I am getting a soft exhaust backfire still so....

 

[Rijko]

Swapping the signal wires for the coils will produce backfires and prevent the engine from running.
Are you sure the coils are connected properly ?

 

[Gorminrider]

Forgot to mention, that in all of this, I did the direct-to-battery/relay mod

. Maybe get rid of that . for the moment, anyways.
and to add to simple good ideas above...
Check a plug or two for spark -replacing with a wee bit of fuel down the spark plug holes...
there's so many simple things to try that i forget half of them and kick myself when a 1/2 forgotten one works...fuse, kill switch...

 

[DesertRatliff]

Swapping the signal wires for the coils will produce backfires and prevent the engine from running.
Are you sure the coils are connected properly ?

Thanks for the response. I just went out and checked the wiring. The coils have two leads on each coil. There is an orange/white wire and a black wire on one and an orange/white and white wire on the other. Orange/white on both coils goes to 12v(+) from the relayed circuit to the (+) battery. White goes to white and black goes to black from the ignition so it appears everything is hooked up properly. For kicks, I switched the signal wires (the black and white) and there was no change; no start, no stumble, nothing.

 

[DesertRatliff]

. Maybe get rid of that . for the moment, anyways.
and to add to simple good ideas above...
Check a plug or two for spark -replacing with a wee bit of fuel down the spark plug holes...
there's so many simple things to try that i forget half of them and kick myself when a 1/2 forgotten one works...fuse, kill switch...

Thanks. I'll try that. I remember adding the relay circuit in such a fashion that I could remove it and go back to stock if necessary without any re-re-wiring. I'll give that a shot. I remember trying a few different relays last Fall to make sure that wasn't it, but don't think I reverted to stock as it appeared the direct-to-battery mod was working as intended. Worth a shot reverting back at this point, though. I might just pull the carbs and at least go through them again to make sure they're not part of the problem. After all, I was troubleshooting all of this with a faulty (and new) Dyna ignition. I definitely need to retrace some steps now that I know that device isn't part of the problem.

 

[rphillips]

Seems at this point anything is worth a try. But if it won't start on starting fluid you'd think it must be the spark...I guess you won't know till you find it.

 

[Gorminrider]

Sure i'd agree carbs can atrophy over a winter but it's a bear getting them out and dissappointing if it doesn't help. .On simpller engines where your plugs are wet and your cylinders smell like gas and it's still not firing, it's pretty surely spark but on these more sophisticated engines, it's hard to get them to flood in that way by just turning them over with a starter.... so Gas down the plugs or if you can easily spray a dose a dose into the airbox inlets might do as well to see if further is needed..

 

[DesertRatliff]

Carbs are pulled. I'll be going through them again.

So that it's all fresh in my mind and since I have a working Dyna S ignition now, I'm going through everything again. With carbs pulled, I figured I'd spray starting fluid directly into the intakes. Bike doesn't start but I'm getting a backfire/afterfire out of the 3/4 exhaust. What could be causing this?

I've got:
-Ignition statically timed for 1-4 and 2-3 where it says is appropriate. Signal voltage is indicated at the F 1-4 window and the 2-3 window on the rotor.
-12+v to the coils at rest, 11+ volts to the coils while cranking
-Coils hooked up to the appropriate spark plugs
-fresh spark wires going to the caps/cut about a 1/2inch off of all four and re-attached to the caps
-new non-resistor NGK spark plugs on all 4 cylinders
-checked and adjusted valves to spec
-spark on all spark plug wires. Not what I would call strong spark, but I do have confirmed spark on all 4 cyl.

Why the backfire with an electronic ignition that's statically timed right, though? I'm scratching my head.

 

[rphillips]

I remember, years ago, I'd had my bike apart & when put it back together it wouldn't start. A friend helped me figure it out & I had installed something on the ign. backwards & the timing was 180 degrees out of time. I,m thinking maybe the spark advancer, I remember it was something very simple & easy to correct.. Just wondering if there's enough plug wire to swap the plug wires on 1 & 2, and on 3 & 4. pretty simple just to be sure it isn't 180 out of time. If this is stupid, just forget it, it's been 40 yrs ago & I can't remember for sure.

 

[DesertRatliff]

Thanks for posting. I've swapped signal leads to no avail but I'll try swapping the rotor orientation around. I thought I did it by the book but something about the firing order just can't be right

 

[DesertRatliff]

Only change with the pickup rotor swapped 180 degrees is a slight pop out of a carb instead of a backfire out of 3/4 exhaust. I'm slowly losing steam.

Glad my 1980 GS850 is running well as I've been enjoying that.