Hi everyone, I am a new rider and just purchased a 96 GS500 with 20,000 miles on it.

Everything seemed fine when I got few weeks ago until just yesterday as I started losing power while riding.
Coming from a stop, I would try to speed up and all of the sudden the engine starts to go in and out where I get power at random increments.

I got the bike from a mechanic and was told to switch to PRIM to see if it helps with that issue. I tried it and it would give me normal throttle feedback, but now the problem is with the engine revving at around 5000 rpm and above as I come to a stop.  Then I would have to squeeze my brakes and let the clutch out to compensate for the high revving.

I've seen similar problems on the threads but can't seem to figure it out.

Carbs have been taken apart and cleaned before buying the bike. gaskets and rings changed.

am I just not setting the idle screw right? is there a leak in the air intake? kind of at a loss here.

I would appreciate any help trouble shooting these problems before I take it into a shop.

Thank you,

Louimart

High revs indicates an air leak or clogged pilot jets.

The common method for checking for air leaks is to spray something like starting fluid around the carbs while it's idling to see if the revs increase. Revs increase and bingo, you know you have an air leak. Check the boots on the carbs for cracks or deformation.

You can warm the bike up and fiddle with the idle set screw to see if it goes away. If you don't get any response from the idle screw then you've definitely got a carb problem.

Thank you Kijona!

I just took the bike for a quick ride and realized the tank was half way empty so I put some gas in. boom... no high revs or loss of power...

Was the engine just not getting enough fuel which lead to these problems?

But before I went to the gas station, I turned the idle set screw both ways... but not much response... I'm starting to think the "mechanic" I bought the bike from might not have cleaned and rebuilt the carb like he said he did...

would carb cleaning fluid be ok for checking air leaks in the carb?
Hoping to do this after work tomorrow.

Thank you again for your response!

I actually came across a small leak...

The bottom screw on in the middle of the picture seems to have oil slowly dripping from it.

And the fuel filter has some tiny pieces of rust or dirt in it. I only see a little but is that bad?


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For starters, get rid of the fuel filter.

That fuel filter is non-standard and now I understand why you were having fuel issues. Since the carbs are gravity fed, having a fuel filter can reduce the flow to the point of having a fuel delivery issue. My guess is that when the tank drops below half or whatever level it may be, it reduces the overall pressure in the system, and thus you have issues. Don't worry about crap getting in the carbs. There is (or at least should be) a fuel filter inside the tank. It's mounted to the shut-off valve under the tank.

As far as the oil dripping...welcome to the world of air cooled engines. Nothing to worry about. If you really want to be anal, you can attempt to tighten the bolt. Don't go nuts with it though.

The idle screw requires a few turns to produce results.

You can use carb spray also but I recommend something a little more flammable like starting fluid. Also, do it when the bike is cold, not after a ride. It will reduce the chance of flame up.

Thanks again guys!

Would you recommend replacing the non-standard fuel filter? If so, which one should I replace it with?
Or should I take RossLH's advice and take it out since there's a filter under the tank anyways.

Thank you for the tip on checking for leak when it's cold... Wouldn't want it to flame up on me!

Fuel filters are very known to cause fueling problems on GS500's. You don't need one.

Quote from: Louimart on May 15, 2013, 09:47:05 PM
Thanks again guys!

Would you recommend replacing the non-standard fuel filter? If so, which one should I replace it with?
Or should I take RossLH's advice and take it out since there's a filter under the tank anyways.

Thank you for the tip on checking for leak when it's cold... Wouldn't want it to flame up on me!

I should have been more clear. Remove the fuel filter, it's unnecessary as there is (should be) a fuel filter in the tank.

Also, carb cleaner may or may not harm plastics so it's best not to spray it up around the carbs while they're on the bike. Starting fluid is far less caustic (just don't breathe it).

I know the general consensus is that a fuel filter is not needed/desireable on the GS but the fact that it has rust flakes in it proves that it IS needed. It is doing its job! It is probable that the intank strainer is missing or punctured and is letting the crud through. The pilot jet is small and easy to block so the cleaner the fuel entering the carbs the better. I have been using twin in-line filters for three years without any problems. I have never touched the carbies from new, not even to adjust the idle mixture. The bike runs perfectly, starts easily and gives excellent fuel economy. As a mechanic for over 43 years I can tell you that the more you fiddle with your machinery the more trouble you will have with it. Keep is as stock as possible, service is properly and often, don't thrash it and it will go forever. Too many people here fiddle and try to get more power so they can go faster. If you want to go faster, buy a faster bike. A standard GS is a very good bike for its designed purpose. If you are happy to spend most of your weekends working on the bike then fiddle away. If you prefer to ride rather than get frustrated with continual  problems then leave well enough alone and enjoy the scenery.

The best way to avoid rusting in the tank other that not letting the rain in is to keep the tank as full as possible, especially when parked between rides. All air contains moisture so the less air you have in the tank the less moisture you have to condense on the cold inside surface. If you park the bike with a near empty tank after a ride on a warm, humid day you will get a lot of condensation on the inside as the tank cools down overnight. I always refill the tank, to the cap, after a ride and therefore there can be no moisture in the tank to cause rusting or to be pushed through to the carbies. A little logic and a few minutes after a ride will save a lot of frustration later on. 

Thanks for the tips guys.

got up this morning to find that my bike was leaking gas... seemed like it was leaking from the petcock. hoses seemed kinda rough too... im guessing its time to change the fuel lines.

again... another thing the "mechanic" said he just changed... fml... the hoses looked fine but i guess its old. I need to bring one of you guys with when i buy my next bike...

Regardless of the fuel leak, I took my bike to work today. Once I used up some gas through riding, the leak stopped completely. Everything else was fine until the ride home. Started revving high again, I pulled over, adjusted the idle screw and seems it has solved that problem.
I am worried though that in the morning when the bike is cold, it might not start or stay on since the idle was adjusted lower.

I forgot to pick up the starter fluid... I'm going to get it in a bit.

Do I need to take the tank off or anything when I spray the fluids around the carb?

Your fuel filter is fine. It can cause starvation ... but 5k is low for a filter that clean.
You may have clogged jets, but pilots are low throttle jets. Under 1/8th throttle. So 5K under load is not your problem.

You have to fix fuel leaks, and not ride with them. Cos you could go kaboom with a stray cigarette tossed out of a car.

I wont use starter fluid on anything. Diagnosis and repair is your only option.

As for the low on gas and getting it act lean - my question is - how low ... I think your petcock in the tank may have had the pickup installed backwards. If you were 4-5 gal to full tank ... then you were plumb out of gas. Good you found out before you had to push it.

Cool.
Buddha.

Thank you Buddha.

What is the pickup??

You said you had gas leaking.

Did you leave the petcock in the PRI position? If so, that is why.

No. I make sure its off Prim when I'm done riding.

I took a look at it before i went to sleep and the knob area looked like it was covered in gas and areas below had gas trailing but it wasnt dripping or anything.

Should i replace the petcock or or maybe just take the petcock apart and change the o-ring in it?
Im thinking i will do all of this along with replacing the fuel lines around it as well. Probably be a good time to reorganize how the lines travel through the body since some of it looks a bit bunched up and pinching each other in some areas.

Would anyone know what size fuel lines and o-ring i need for petcock on a 96 gs500?

Thanks guys for your continued support!

Louimart - This fuel line from MotionPro is terrific. It's very flexible ad won't harden. The 1/4" is a perfect fit for the GS. You can order it direct. You may be able to get it from a local shop a little cheaper. It's the best stuff I've ever used.

http://www.motionpro.com/motorcycle/partno/12-0052/

Quote from: Louimart on May 16, 2013, 06:07:40 PM
Thank you Buddha.

What is the pickup??

Plastic screen and pick up - sits inside the tank. Take off the tank petcock and its there. The longer plastic part needs to be toward the back of the bike if the screwdriver slot is facing right.

Cool.
Buddha.