GS850 running poorly - troubleshooting igniter and coils?

[Chuck78]

My buddy picked up an 82 GS850 (81 GS850 engine with 82 GS1100 ignitor/coils). The bike was running good for a week when it started getting harder to start and not wanting to accelerate. I rode it and it was fine at 1/4 throttle, but accelerating and holding throttle at half or more, it would rev, bog down (noticeable change in engine pitch), then rev up, bog down etc. I thought it was just clogged carbs or lack of fuel supply. Tank turned out to have lots of rust debris. tore down carbs completely (but did not separate them off rack), blew out all passages, found some fine rust particles in bowls and a few chunks of crap behind the needle and seat screen filters. cleaned and sealed gas tank. new inline filter.

Runs better, but still hard to start and still doesn't always like to rev. Now and again it does take off like a bat outta hell for a few seconds, but often when revving it, it blows out a lot of black exhaust smoke, and backfires a lot, sometimes just popping sometimes shoots flames out the mufflers.

I can't remember where I found the procedure to ohm out the low voltage and high voltage sides of the coils, but plan on doing that. It is really the electronic advance ignitor box that I am very suspicious of even before we found all the rust in the gas tank. What would symptoms of a failing ignitor be? It seems like an out of time spark from failing electrical components in the igniter would create running issues like these. All help appreciated. This bike has 7,000 miles on the engine and is a beauty, and this guy is dying to ride the thing with us ASAP! HELP!

[Chuck78]

Carb diaphragms looked great, carbs cleaned, he's played around with the idle/low speed mixture screws, but those shouldn't have much of an effect on the 1/2 throttle or greater running anyways. I am really thinking it's a failing igniter. Any further troubleshooting help?

Can you swap a mechanical advancing Dyna S or Pamco electronic ignition conversion into a bike that had the electronic advance ignitor setup? Or is buying just a new igniter the preferred way to go? I offered to have him buy a Pamco ignition and ttry it out, and if it wasn't the problem, I could buy the Pamco off him to replace my 1977 GS750B points setup.

Plugs get really really sooted up in this running condition, and putting the timing light on, it's hard to get the thing to flash consistently on all cylinders. Have not tested wires, but did pull plugs and crank to see spark on all 4. May not have been the brightest though. original GS1100 coils, 20-30000 miles?

[rustybronco]

but often when revving it, it blows out a lot of black exhaust smoke, and backfires a lot, sometimes just popping sometimes shoots flames out the mufflers.

An igniter isn't going to make it blow black smoke out the exhaust. It might make it back fire, but will have nothing to do with excessive smoke. Shoots flames out the back? excessive fuel welling in the exhaust. Think about it, no spark, not capable of making black smoke

Plugs get really really sooted up in this running condition, and putting the timing light on, it's hard to get the thing to flash consistently on all cylinders.

What do sooted up plugs indicate to you?

Sounds fuel related... Tear the carbs down, do them properly and go from there.

[Chuck78]

Carb jets & needles are stock for the gs850, intake & exhaust stock, black smoke would indicate too rich at half to full throttle, so the only variable left would be the needle/seat not sealing, but thsy looked good to the eye & touch. Unless someone got mixed up on jet size ratings, as dynojet etc use different numbers than oem mikuni

I was thinking that the electronic advance or timing in general could be way off due to deteriorated resistors diodes transistors etc, maybe not always firing every cylinder consistently?

[Killer2600]

I was thinking that the electronic advance or timing I'm general could be way off due to deteriorated resistors diodes etc, maybe not always firing every cylinder consistently?

I could be wrong but I believe in '82 all the zuk's had mechanical advance. In '83 is when I believe they went to electronic advance.

I'm with rusty, definitely sounds like a fuel issue. Ignition issues are more like miss fires and ignition cut outs that are not dependent on throttle position nor do they feel like variations in throttle when they occur.

[Chuck78]

I thought it may be a problem with the ignition advance and/or timing. maybe the ignition is off of an 83 then, it is definitely electronic advance. also should note that we removed the air filter and it still acted the same, the filter is not clogged. if the vacuum diaphragms are not raising properly then I would suspect only for it to be running lean, and it would appear to be running way too rich. It does act as if it is starving for fuel as it will rev up and then bog down and then rev up and then bog down, but holding the throttle open it will blow out black smoke at high RPM's with maintaining a constant half throttle. the only thing I can come up with is the needles and seats are not seating properly, & it is just flooding out the carbs. unfortunately they do not have a hose attachment like some bs32's to check the fuel levels from the fuel bowl drain

[Killer2600]

I thought it may be a problem with the ignition advance and/or timing. maybe the ignition is off of an 83 then, it is definitely electronic advance. also should note that we removed the air filter and is still acted the same, the filter is not clogged. if the vacuum diaphragms are not raising properly then I would suspect only for it to be running lean, and it would appear to be running way too rich. It does act as if it is starving for fuel as it will rev up and then bog down and then rev up and then bog down, but holding the throttle open it will blow out black smoke at high RPM's with maintaining a constant half throttle. the only thing I can come up with is the needles and seats are not seating properly, & it is just flooding out the carbs. unfortunately they do not have a hose attachment like some bs32's to check the fuel levels from the fuel bowl drain

It's not possible to just swap an '83 ignition into an older bike. FWIW my '82 has electronic ignition with mechanical advance, it has pick-up coils under the ignition cover which has the mechanical advance mounted behind it all and an electronic ignition module under the right side cover.

Personally I'd do an in-depth carb disassembly, dip, and clean with fresh o-rings to boot.

A side note: black exhaust doesn't come out the tail pipe of an engine that isn't firing and lighting the mixture, an over abundance of fuel and a spark to start the fire/smoke has to occur first.

[rustybronco]

I could be wrong but I believe in '82 all the zuk's had mechanical advance. In '83 is when I believe they went to electronic advance.

'82~up GS850 and GS1100G's had electronic advance built into the ignitor module.

[GSOH]

I appreciate everyone chiming in here to try and get this resolved, after all this is my bike

So, after topping off the gas tank this morning, leaving the cover off to make sure it wasn't blocked (further tearing it down and it appeared to be fine) the bike starts fine. Started right up in fact. Still spitting out some smoke in the garage (no road test). I have noticed that revving the throttle up to about 5-6k rpm it, it will slowly creep back down on the tach, level off at around 1800-2k and then almost instantly drop to about 3-600. From what I read on the koolaid_kid help page for 'Adjusting Idle Mixture Screws on CV carbs', this would indicate either a hanging idle or it is running too lean (not rich as we were thinking). I was thinking that heavy soot on the plugs was a sign of running too rich, not too lean

Thoughts? Right now the idle mixture screws are set at out 2.75 turns out (started at 2.25 then 2.5 then moved to 2.75 and also soaked air filter in hot dish soap water and I thought it may have been over oiled).

I read on post #8 over here that worn needle jets can cause bike to run rich in mid range: Is there a physical check to see if valves are worn? http://www.thegsresources.com/_forum...d.php?t=209223

[Chuck78]

I'm pretty sure rich got these carbs from a different model bike and fitted them with the proper jets and needles as stock 80-83 gs850 bs32 specs, & replaced the o-rings throughought the carbs.

tonight I would like to remove the air box and run the bike, so that I can open the throttle and let it rev up and watch what the needles& slides do to determine if the diaphragms are working properly and rising or if there is a hole in them or a leak somewhere. I would also like to make sure that they are Mikuni jet sizes and not Dynojet or something that uses similar numbers to designate a totally different size

[Chuck78]

if that doesn't tell me anything conclusive then the next step would be to find some fuel bowl drain adapters to check the fuel levels while the bike is running.

apparently PAMCO Pete no longer has a website for GS ignitions systems, only Yamaha and a small sidebar mentioning Honda parts available. bummer because I was really impressed with his product line, and had planned to eventually swap his ignition onto my bike

[rustybronco]

I appreciate everyone chiming in here to try and get this resolved, after all this is my bike

Take them apart... take them apart...

It will only run correctly with the air box on..

Black smoke is running rich.

You can measure the float levels after you reassemble the carbs.

Double check the jetting while the carbs are apart.

Check your intake boots and o-rings while its apart.

Reseal the air box if you haven't already.

[Chuck78]

It was still blowing out black smoke at 3/4 throttle with the air filter removed... We had the carbs apart once, the main jet that I looked at might have been marked 112 but I think stock is 110 but I really couldn't be sure of the markings. with this I would say that maybe the needle/seats are not sealing or the float levels are just off but we checked one and it was dead on & carbs were just gone through by previous owner.

[GSOH]

Coils test out at 4.5 primary &12.5 on secondary. Service manual calls for 3-5 & 30-40k. Could this be reason engine is running so rich? PO installed coil relay mod.

I'm thinking IF I need new coils, would these do the trick? http://accel-motorcycle.com/motorcyl...ils-black.html

EDIT: 850 Service Manual calls for 4 ohms on the primary and 15k ohms on the secondary. The above is for the 1100 coils.

[rustybronco]

Could this be reason engine is running so rich?

Nope......