DESPERAT CRY FOR HELP!! Calling all GS500 Experts

[liquid0715]

HI ALL!

I bought my bike last year and am a beginner rider and owner.   Currently, my bike is going through the right cylinder spark plug like a 1 year old goes through pampers.  The bike is at a professional shop for the last 2 weeks and they can not figure out what the problem is.  The bike has an open K & N filter setup and bigger jets than stock.  The carbs are clean, the valves just got readjusted and my bike is still managing to foul the right spark plug.  The left side is fine.  I foul the plug in less than 5 miles.
The shop suspected the choke getting stuck, that was not it.
Checked out the carb, everything was good.  They noticed the carb had 2 different size mixing screws when they first got it but replaced the screw with a matching correct size.  The wires are okay.
They are stumped and I am just frustrated.  I searched for similar topics on the forum and all of the suggestions that were made have already been checked out according to the shop.  The float bowl heights are correct.

This is either a very stupid problem that everyone is overseeing or its complicated enough where the only person that would know the answer would be someone that experienced the problem.
A lot of people on the forum seem to have the left cylinder fouling but mine is the right side.  I do not know anything about bikes so PLEASE HELP so I can go out and ride whats left of the almost over summer.

[joshr08]

more info on the bike would help year. mileage.  coil taking a sh!t?  have they done a compression test? 

[liquid0715]

1992 gs500, about 19,000 miles.
Compression test was good.
Coils are good.  That was the first thing I can think of was no spark.

[scottpA_GS]

The bike is at a professional shop for the last 2 weeks and they can not figure out what the problem is. 

Not a very "professional shop" then... Take it somewhere else  I couldnt imagine someone Im paying and trusting to fix my bike telling me... We dont know what it is...  

[liquid0715]

I can not disagree but they have been very nice and patient with my needs ever since I got the bike.
They are puzzled themselves, and havent asked for a dime yet for this problem.

[joshr08]

it has to be a carb set super rich or an intake valve stuck open to foul a plug that fast if its getting good spark

[bigfatcat]

How do you (they) know the wire is 'ok' ?

A weak / intermittent spark can let a plug foul,  making you think you've got carb/oil fouling problems.

Is your bike down on power ?

I'd look to the ignition circuit 'cuz seems like everything else has been covered.

[liquid0715]

Joshr08,

How is a carb set too rich?  do you mean larger jets? different mixing screws?

BigfatCat

Once the plug fouls you can tell the bike does not want to move below 4k RPMs.  Once I'm over 4K it really does not matter whether the plug is fouled or not.  But initially with a brand new plug the bike moves.  After a couple of miles of riding the bike feels like its bogging below 4K when you hit the throttle, say from a complete stop.

[joshr08]

different jet/bad diaphram in the top of the carb/needle set different/air mix screw set wrong/ not synced right

[liquid0715]

I am guessing all of those things you mentioned can easily be spotted at a professional motorcycle shop with just the carbs in their hand to play with?

I know I wont be able to tell unless I am guided step by step.

Does the gas I put in make a difference?  I have been using 87 octane.  Although if gas was the problem iit would be fouling on both cylinders.  The one cylinder is the key here.  The left side is fine, the right side is not, so I guess something has to be different than the left. 

What can really be different on the right cylinder/carb that a motorcycle shop might overlook?  Can I exchange the coils to see if the problem switches sides?

[joshr08]

yes coils can be swapped to see if it changes sides or stays the same

[Bridger]

Plan A: Sell it with new plugs....JK  Plan B: I would certainly agree that you have a carburetion problem.  I ,personally, would just rebuild the carbs and inspect/rejet them as per the recommendations laid out in the wiki and see what happens.  It's definitely not gonna hurt, lol.

[jeremy_nash]

I had a problem with carbs fouling out after maybe an hours time on them due to the tank liner dissolving in the gasoline.  changed tanks, problem went away.but that was on both cylinders, so shouldn't be your problem.   I would swap coils, and see if the problem moves with it, if it does, then you've found your problem

[liquid0715]

THanks everyone for the ideas.  Keepin Comin 
As I was writing on here is when I thought about exchanging the coils.  The carb was worked on so much I feel like the problem can not be there even though everything points in that direction.  I think they tested the coils and they got spark and moved on but i dont think anyone tested to see if it was consistent.
HOw does the coils work in the GS500?  Is there a timer that sends the spark every so many seconds.  I mean in a car it is the distributor cap that controls the spark and timing.  All we have are two coils, what controls the timing? 

[jeremy_nash]

there are pickup coils under the cover on the right side of the bike. 

[Chanse]

crash history? right low side? broke loose a pick up? it would only have to be off a few milimeters to deminish the spark.... Oil fouling plug, or gas? I know you said the wires are ok but how old are they. I have seen "ok wires" in a car look good and have no significant damage, but turn the lights off and watch the sparks jump right out of the wires. Crazy little light show. umm. I'm also leaning to jet size for some reason. What is your bike jetted at? What is the set up on the bike K&N replacement or lunch box, Jet size ?, Stock, after market, or stock modified (slip on)?   +1 on the swap coils check....   and the gas should not matter the manual just states "87 to 91 octane". so any of the three would be fine. Thats all I can think about right now. Been up since midnight at work... ITS FRIDAY BABY. YEAH.......

[liquid0715]

THe history of the bike is a problem.  I do not have it.
When I purchased it 2 years ago it wasnt running.  Mainly due to dirty carbs & a bad tank.
Had the shop clean the carbs and Buddha sent me a used coated tank.  Any problems due to the tank would result on both cylinders fouling.
I do not know the jet sizes, all I know is they are larger than the stock ones.  I have a K & N setup that came with the bike, straight K & N on the carbs, I believe the "lunch box" setup.
Stock exhaust.  I can find out the jet sizes from the shop.

[08GSSteve]

When the shops said they have looked at your carbs ask them if they pulled them apart fully?  A shop where I USE to take my bike say they have cleaned the carbs but all they do is spray a can of carby clean down the throat.  For a shop to fully strip down your carbs will cost you a packet (do it yourself if you are able and mech inclined).

It will not hurt to take the bike to a different shop regardless of how patient and nice your local is.  Is strange such a simple engine configuration has a pro bike shop stumped when they deal with complex EFI engines every day.

keep us informed, good luck

[lopee]

How do you (they) know the wire is 'ok' ?

A weak / intermittent spark can let a plug foul,  making you think you've got carb/oil fouling problems.

Is your bike down on power ?

I'd look to the ignition circuit 'cuz seems like everything else has been covered.

+!

[bassmechanicsz]

Just out of curiousity where are you located as someone on this board might be local to you and be able to offer better advice actually seeing the bike first hand and help you learn about it at the same time.