Wont rev up at all--Timing? What is the deal here?

[GSstiny]

Ok, this is going to be long, I apologize in advance.

Last thursday I rode about 50 miles home from class in POURING rain. about 10 miles from home it started hesitating and running funky when I accelerated. I assumed it was just a wet plug and no cause for concern. Friday I had to go about 10 miles to a job interview and had the same problem, hesitating worse and worse, until it wouldnt rev up to pull out at all. I got home and pulled the plugs, and all 4 look fine, a bit rich on 2&3, bit lean on 1&4, but not severe. I had been trying to get by with 87 octane gas, so I drained the full tank of 87 :shock: and went to fill up with 89. After topping off it started after much cranking, but wouldnt rev up at all. When I gave it throttle it would just die. So I hauled it home and let it sit over the weekend.

Now, today. Same problems. Cranks alot, but will start, idle is reasonably smooth, but it WILL NOT rev up at all. any movement in the throttle causes it to die. Plugs are fine, although they have about 2k miles on them. Petcock is allowing fuel to flow. Vaccum readings are not good, indicative of weak valve springs, but that isnt news. All cylinders are firing, but spark is very weak. Im assuming both coils didnt crap out at exactly the same time. Points are not burnt, gaps are correct. Im inclined to think that its electrical, because it came on all of a sudden.

Here are my possible diagnoses at this point:
2 bad coils--Unlikely, but possible. Of course the damn dealer is closed on monday so I cant get them tested until tomorrow.

Electrical timing out of whack--Possible, but Im unclear as to how to adjust/check it and I hope you all can help

Bad condenser(s)

Cam chain has jumped/broken a tooth allowing the valves to open at the wrong time--jeez I hope that isnt it.

If youve read this far, thanks. If you can offer any suggestions, Id be eternally grateful

[onchiman]

Check your plug wires. My last set were done in by being caught in the rain. They were cracked and water got in there and caused arcing. Poof, they were gone.

[chef1366]

Doubtful on the cam chain tooth but more then likely a points problem. Check you points gap and check the actual surface of the points for melting or curvature. If they are melted it could be a condenser. The breaker point gap should be between .012in - .016in. Turn the motor until the cam lobe has the points open at its greatest gap and check gap with a feeler quage.

[GSstiny]

the points contacts look almost new and I double checked the gaps to be sure. Still coming in at about .014 in, right where it needs to be.

I hope its plug wires. How do I check the actual resistance on a wire thats made into the coil like this?

Dont mean to sound stupid, but motorcycle electrics are new territory for me

[semerm]

any rust in the tank? Do you use a filter? I'd suspect a clog somewhere in the gas supply.

[yogib]

Stock airbox?Maybe the air filter is soaked and hasn't dried out yet,or collasped.Easy check.

[GSstiny]

Im using the stock airbox & filter, I looked at it while I was stranded friday, and everything seemed cool. Getting a little dirty, but cool.

I dont have a fuel filter, and i dont *think* there is any rust in the tank, but I cant discount the possibility of tank crud plugging up the carbs. I have new orings en route, so unless I find an ignition problem Im just going to clean and reseal the carbs. They need it anyway.

[chef1366]

ZZZap

I check bad wires by spraying water on the wires at night or in the dark and check for arcing. Don't spray the water while the motor is running;-)

[can.wrench]

Did you remove the breaker plate and check the manual advance? If it's stuck (rusted?) bike wont rev. Also drain your flotbowls an' catch it in something plastic look for rust or water. Good time to change those wires and coils and ignition- Ilike the Dyna. Did you do a compression test? Might have a couple tight intake valves, But thinking it will be electric in nature.LUCK.

[headsbikesmopars]

Sounds like a lean out to me. Idles ok but won't take the throttle. Might have nothing to do with getting wet. Check out the mains. I have seen them fall out into the fuel bowl and give the same symptems as yours. Check the easy things first. Also a rich mixture takes more spark energy to fire..IF the coils are soaked...try a hair dryer to dry out the electrics. Wet air filters fatten up the jetting too and week coils can't fire the mix. Good luck, I'm sure you will find it and please post when you do. Valuable to others here. Terry.

[GSstiny]

OK, heres the fun for today, and I mean FUN. I drained the carbs to check for rust/water, and everything's fine. Magically, it fires up, pops, sputters, and generally runs like ass, but at least it revs up some. Carb drains are dumping gas like mad, so Im thinking its been carbs all along. I pulled the coils and had them tested, both of them are fine.

So, I get to work pulling the carbs and after a heroic struggle with the intake boots from hell, everything's apart. Seeing as how its going to be down for a couple weeks, I decide to park the remnants of my bike behind my apt building. There is about 6ft between the buildings, so its a bear to wrestle it back in there. I finally get it where I want it, and start to pull it back on the centerstand. Well, oil/grease on my hands, and being ****ed off, you know what happens. The frame slips out of my hand and over she goes, hitting the other building on the way down. The carnage? Toasted mirror and maybe taillight to boot. After a stream of obscenities, I start to pick it back up. The maintenance dude, who was standing (not working) no more than 20 feet away DID NOT EVEN OFFER TO HELP. Arrrghhh. One of those days.

Ill post back when I actually get it fixed or sell it for scrap and buy an SV, whichever happens first.

[chef1366]

Couple days

Take a deep breath and maybe a couple of days will give you a better attitude. I'm putting a couple of mirrors from my 80 1100 on ebay tonight, do a search of GS1100. Tail lights are on fleabay all the time. Buy a K&L rebuild for new float needles and seats. Check and double check float adjustment.

[GSstiny]

Thanks for the heads up chef. After posting that I dug into my roommates vodka stash and watched a little TV, calmed me down pretty quick.

Just so this post is relevant to the problem at hand, Im now 2 carbs in to a rebuild and no obvious problems/excessive junk yet. At this point the plan is to replace the plug wires and caps (theyre original) and get the carbs reassembled, then go from there.

[GSstiny]

OK, all the parts are here, the bike is reassembled. I cleaned every little passage in the carbs, and for the most part, they were spotless, aside from the toasted orings. I put all adjusting screws right back where they were. While it was down I also replaced the original plug wires, caps, and just for good measure, the plugs. It started up fairly easily, and runs ok on the choke. Unfortunately if I ease the choke off at all it dies. Any application of throttle causes it to die too. Its also backfiring through the carbs.
Could it be something in the valvetrain is going seriously south?

[GSstiny]

Im reviving my own thread here, but with good news. I talked to the only decent bike mechanic around here and he said to check the connections from the wiring harness to the coils. He said his old GS had the same problem, and it turned out that through years of getting hot and getting cold the spade in the connector had lost its spring and wasnt making good contact. I pulled them apart and smeared dielectric grease on them until I get home to replace the connectors. It fired up and revs fine now.:-D

Hope this helps somebody in future searches.