Pluuling my hair out/ help!!!

[davidjasbridge]

Ok, ive been pouring over this site for a week now, I think I got it figured out but I would like some input for the gurus here. My problem is my bike ran great(81 gs650g only 20k on it), was on a ride and was comming into town doing about 45 in 5th, the bike sputtered some and didnt have the right throttle response. I downshifted and the bike pulled out of it and ran fine, I figured it was time to clean the carbs again because of the rust in my tank, didnt think much of it. I park the bike for about an hour. get back on it and when I start the bike up it has a slight miss, and my friend noticed some fuel dripping out of the airbox plenum, I road for 5 mins with no performance issues until I came to a stop, then it was spitting and sputtering like crazy, and running like it had a dead cylender. So I tore down the carbs, cleaned em, put em back togeather, same. tore carbs down again, re cleaned em, was VERY meticulous this time, there perfect. I bench synced em, (feeler gauge) and still nothing.
This lead me to believe that its a ignition system issue, coils passed ressistance checks, primary and secondary, signal generator passed. but when I did the ignitor test I had no spark fire on either applying the probe or removing the probe. is there any other way to test the ignitor? this was the only test my book gave for it. Any help would be much appreciated because this is my commute ride and the 50mpg is the only thing making my 500 mile a week commute worth it.

[7981GS]

Anything.




Eric

[davidjasbridge]

ok I have spark at the plugs, not fat blue but blueish. could the unit run fine cold, then once it got a little heat start to fail? or am I barking up the wrong tree?

[davidjasbridge]

or do I need to check into fuel delivery again or start checking valves and such? Valvetraine isnt noisy, slight valvetrain noise not much though.

[Killer2600]

Check the voltage to the coils (should be close to battery voltage) and check the grounds for the ignition system (voltage drop should be less than 200mV).

Fuel coming out of the air box sounds like a carb float problem, make sure the seat is clean and the valve is seating and cutting off fuel flow. Also make sure the float still floats.

[BassCliff]

Greetings and Salutations!!

Hi Mr. davidjasbridge,

The electrical section of my little website has ignition troubleshooting procedures. You'll find the proper carb cleaning procedures on my website too. When was the last time the valves were adjusted? A thirty year old motorcycle needs maintenance. Let's get started...

Let me dump a TON of information on you and share some GS lovin'.

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Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

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Thank you for your indulgence,

BassCliff

[tom203]

You don't still have a 81 petcock right???? You say you got spark,so it sounds like fuel delivery problem. Test petcock- make sure it can deliver fuel when it's supposed to. No fuel in vac line! disconnect vac line and suck on it-does fuel flow nicely and not towards your mouth?

[davidjasbridge]

Carbs are clean, when I got the bike back in september I used this site as my bible, back then I had to clean the carbs cause the bike sat for about 15 years. So yes the carbs are clean, went throught the 31 year old petcock, clean, new oring. Got the bike running by bypassing the wireing harness and wired the coils to the battery. Now the bike starts and idles fine but when I ride it I hit that 6000rpm ceiling I was reading about, bad ignitor? I did the resistance test on it and it passes, could it still be bad?

And thanks cliff, you have been more help that you can relize( got all my knowledge about these bikes on this site, I refer to it as my bible!)

[davidjasbridge]

I havent check the valves yet, the thing only has 20k on it, so I wasnt to worried, but it is on my list of things within the next 5k

[Nessism]

David, please check the Newbie Mistakes thread linked in my signature and see if anything strikes a chord. It's disturbing that you haven't adjusted the valves and your tank has rust in it yet you dismiss these critical details.

Until you go though all the bikes basic maintenance you are going to be grasping at straws as to what's wrong.

[davidjasbridge]

will do, i did run the bike on an alternate fuel source(1 lieter bottle) and it did the same, and there is very minimal valvetrain noise. My 97xr250r has more ticking than this ole girl does

[Nessism]

will do, i did run the bike on an alternate fuel source(1 lieter bottle) and it did the same, and there is very minimal valvetrain noise. My 97xr250r has more ticking than this ole girl does

The valves on GS bikes TIGHTEN with mileage, they do not loosen and clatter. Once the valves tighten enough all the clearance goes away and the valves hang open all the time...until they burn that is. A noisy valve is a happy valve, so if your valve train is quiet that may be a bad sign.

[davidjasbridge]

good to know, thanks

[davidjasbridge]

but that aside, bypassing the stock wires made the bike run, now it just hits that rpm ceiling and misfires when it does. Would valve clearance do that? kinda like floating a valve?

[Nessism]

Is the airbox and air filter installed? Is the airbox sealed so no false air can enter? Is the filter clean and properly oiled?

The rpm celing could well be the ignitor, but it's most likely carb related.

Did you replace all the carb O-rings when you cleaned the carbs? Did you remove the idle mixture screws, and if so, how many turns open are they? And are the pilot jet plugs in place?