GS850 running poorly - troubleshooting igniter and coils?

[Chuck78]

Not sure what coils are on it, if they were the GS850 coils, they are supposed to check out at 14K ohms on the secondary side, if they are GS1100 coils, they are supposed to be 30-40K ohms. His are reading around 11.9K and 12.4K ohms. I didn't seem to think this was too far out of spec to cause the issues his bike is having. Again it's an 82 GS1100GL with an 81 GS850G engine fitted with the later electronic advance ignition.

[Chuck78]

We looked at it for a few minutes between jobs today, as I wanted to see the vacuum slides operating while it was running - with airbox off so I can watch them rise.

As I would roll the throttle on, I could clearly see the slides doing exactly what they are supposed to do - rise as engine vacuum builds upon throttle opening. When they would get to about 40% open, I believe all cylinders were popping out of the carbs (like minor backfire) and the rpm's would drop and the slides lower down as the engine began running poorly. If I would try and open the throttle a little further than that, then I would start to get the louder popping/backfiring out of the exhaust.

My ASE certified mechanic friend who claims to know only fuel injection and computer stuff (learning like I am on the carbs and older ignitions) also seemed to think as I initially did that this could be an ignition timing issue. A very late spark could cause it to backfire and potentially soot up the exhaust, could it not? It seemed as if the spark timing could be going all over the place as the advance would start to kick in, as if it was going haywire.

The other area I was probing at is the needle spec and setting. these problems occur beyond 40% throttle opening or needle/slide rising. I gathered three sets of carb specs for 80+ GS850's. 2 of them are just the jet needle part number. the third was what I expect, part number for needle, hyphen, then the clip notch position for that particular bike as tuned from the factory. Could it be that when the previous owner went to put these needles in (said he replaced jets and needles to get the correct GS850 spec on these non-GS850 BS32's), maybe he was looking at the specs that did not give the needle height setting, and he just winged it and set it higher than what it could handle?

My snap ring pliers would not reach all the way down into the slide to disassemble them to check position and part number, but tomorrow my mechanic friend is going to bring some snap ring pliers over so I can check this.

The valves were supposedly all checked for proper clearances, and the carbs have all new o-rings and intake boots and were thoroughly cleaned.

I am very tempted to just order a Dyna-S or see if Pete still makes his PAMCO ignitions for GS models (primarily does Yamaha XS's), and swap it onto this GS850 first to see if we can eliminate the ignition. My findings today with the intake vs exhaust backfiring are steering me back towards the timing. Please let me know what you guys think.

[tom203]

Just to be clear. The stock coils should have about 4 ohm primary, 12 kohms secondary ( with plug caps removed). With caps on, you'd likely get about 32 kohms with stock caps, while some aftermarket caps would give a reading of around 24 kohms.

With airbox off, the CV carbs won't be happy as throttle opens- at some point they will do exactly as you describe and the engine will stumble.

[rustybronco]

Just to be clear. The stock coils should have about 4 ohm primary, 12 kohms secondary ( with plug caps removed). With caps on, you'd likely get about 32 kohms with stock caps, while some aftermarket caps would give a reading of around 24 kohms.

With airbox off, the CV carbs won't be happy as throttle opens- at some point they will do exactly as you describe and the engine will stumble.

The stock plug caps should read around 5K each. They have been known to read as high as 10~11k as they age.

[Nessism]

Just to be clear, the 1982 GS1100 has an ignitor with the spark advance built in. You need to remove the centrifugal advance unit from the 850 engine and switch over to the non-advance 1100 set up.

Another option is a Dyna S with the 850 advance unit.

[Chuck78]

Yes the 81 engine has had the original mechanical advance replaced with all electronic advance parts, the pickups and ignitor.

[GSOH]

I tested the ignition system tonight to try and whittle this down. Here is what I found:

battery: 12.52v (new AGM battery)
voltage to coil wires (coil relay mod installed on both coils, key on): Left: 11.74v Right: 11.73v
coils (both were same when testing): primary: 4.5 ohms secondary (no plug boots): 12.5k ohms
signal generator: green-black: 169.3 ohms, black-yellow: 168.7 ohms

Ignitor test: well, I tried Mr. Bill Ricks method and the service manual for 82 1100. left #3&4 in, pulled #1&2, ground to (gulp) painted engine. with key on, connected + blue and - yellow on boot going to ignitor to try and spark #1. nothing. connected + green and - black for spark at Cyl#2. No dice.

I've taken a few photos to try and better illustrate (and troubleshoot). I wanted to test ignition system before checking needle jets and fully tearing carbs apart (again) and get some opinions.

[GSOH]

Ok. It's been a while since I have posted on here (and tore back into the bike). I'm still having issues, particularly with the idle and cylinder 1. It is driving me bat shvt crazy and I'm hoping someone on here can help me nail this down.

completed thus far:
sealed tank
new plug boots & chopped wire ends
carbs thoroughly cleaned
New intake boots & o-rings
new float needles (and required oil change due to gas in oil) with new o-rings
Dyna S DS3-2 installed (12.9v at battery. 11.6v at coils with relay mod)

Also, there is an aftermarket gravity-fed petcock on this. The vacuum port on carb 2 is sealed with a cap.

I started with idle fuel mixture screws at 2.5 then 2 and they are out at 3 in this video. I've set the idle screw at 1300 rpm but it wont stay near it, often diving to 500. I was wanting to get this taking care of before setting timing (perhaps that is a bad idea?). I was under the impression after reading kool_aid kids CV idle mixture steps, a hanging idle indicated a lean mixture, which is why I back the screws at to 3 turns. Maybe its a high idle caused by something else?

Another issue I am having is very intermittent nearning non-existent spark (at least based on hardly any light with timing gun) on cylinder 1. 2-4 all flash solid with gun.

video link

http://youtu.be/ic0NwtXD3z0

[cowboyup3371]

I don't see on your list that you replaced the orings behind the carb boots as that's one cause of it.

Also, try clipping off about a 1/4" of the end of the number 1 spark plug wire and then put the boot back on. Sometimes you might just have a bit of corrosion on it and need to trim it. You can also try swapping coils (swap the connectors I believe but do a search on it) and see if your spark problem follows. That can tell you if it's a coil issue or not.

[GSOH]

I don't see on your list that you replaced the orings behind the carb boots as that's one cause of it.

Also, try clipping off about a 1/4" of the end of the number 1 spark plug wire and then put the boot back on. Sometimes you might just have a bit of corrosion on it and need to trim it. You can also try swapping coils (swap the connectors I believe but do a search on it) and see if your spark problem follows. That can tell you if it's a coil issue or not.

I forgot to include both of those in my list [updated below). Next step was going to be swapping could & connectors to see if that causes it I run any different (better).

[cowboyup3371]

Hey GSOH, I just realized you tagged onto Chuck's issue here.

If I may make a suggestion, please make your own thread about your issues so we don't take away from Chuck's. For one, it can confuse people as to who we are talking about and two, yours could overshadow his since they may not be the same thing.

[GSOH]

Hey GSOH, I just realized you tagged onto Chuck's issue here.

If I may make a suggestion, please make your own thread about your issues so we don't take away from Chuck's. For one, it can confuse people as to who we are talking about and two, yours could overshadow his since they may not be the same thing.

I guess I should clarify, Chuck started this thread for my bike.He has been helping methe last few months on my 'project.'

[GSOH]

I swapped plug wire 1 to cylinder 4 and vice versa. PRIOR to the swap, timing light was intermittent on cylinder 1 and very strong continuous on cyl 4. After swapping, cyl 1 has no timing light & cyl 4 is erratic at best.

Any ideas? Bad coils? Bad plug wires?

[Boxxiebox@08]

was this problem ever resolved ? i have the exact same problem with my 81 gs850gl

[Boxxiebox@08]

Can anyone say with 100% certainty that the igniter unit test recommended in the service manual works for diagnosing weather or not it's good or bad ? I've owned quite a few gs850's with not very good results !