Hello GSriders,

I am Xasuntox. I live in Belgium and i'm 20 years old. I am also an engineering student.
I ride my GS500 for a couple of weeks now. I have the Gs500E 1991 model. Recently I installed a new race/sport exhaust. The next problem is my engine runs a too lean.

First of all, I am a student so I want to do everything as cheap as possible. I just have basic tools to work on my bike.
What do you guys recommend me? I have a stock airfilter, the only 'tuning' is my exhaust.

1. Is it possible to just set the gasneedle at his highest position to make the engine run rich enough? And what is the perfect/ideal position for my mixture screws (how many turns out)

2. What if solution one doesn't work, which jets will I need to fix it? And also, what is the perfect/ideal position of the mixture screws.

Yesterday I tried to fine tune my carbs but it didn't worked out very well. The mixture screws are now fully turned out. But I have the idea my motorcycle is a little bit more lazy now and de mixture is still too lean.

I hope you guys can help me. Thanks you!

See...another perfectly good bike is now screwed up!

There is a definite pattern here!  (If you read the 10,000 or so posts of guys who get into "rejetting"....


Cookie

Quote from: Xasuntox on July 09, 2015, 01:44:01 AM
Hello GSriders,

I am Xasuntox. I live in Belgium and i'm 20 years old. I am also an engineering student.
I ride my GS500 for a couple of weeks now. I have the Gs500E 1991 model. Recently I installed a new race/sport exhaust. The next problem is my engine runs a too lean.

First of all, I am a student so I want to do everything as cheap as possible. I just have basic tools to work on my bike.
What do you guys recommend me? I have a stock airfilter, the only 'tuning' is my exhaust.

1. Is it possible to just set the gasneedle at his highest position to make the engine run rich enough? And what is the perfect/ideal position for my mixture screws (how many turns out)

2. What if solution one doesn't work, which jets will I need to fix it? And also, what is the perfect/ideal position of the mixture screws.

Yesterday I tried to fine tune my carbs but it didn't worked out very well. The mixture screws are now fully turned out. But I have the idea my motorcycle is a little bit more lazy now and de mixture is still too lean.

I hope you guys can help me. Thanks you!

Welcome to the site X!

You really shouldn't need to change too much from just swapping out you're exhaust.... and the mixture screws really should not be out more than three and a half turns - ever. But it's tough for me to say since the carb specs in Belgium could vary greatly to what's around here. Have you seen the Wiki yet? Lots of good info for jetting changes there.

I believe Belgium has 40/125 jets with adjustable needles stock.
You could try lifting the needle 1 clip, and setting the air screws to 3 out.
If you have a good clean stock filter in the airbox, it should work well. In fact we jet US bikes to 40/125 with your set up.
If you're still lean, you may have a vacuum leak.
Cool.
Buddha.

Clean air filter gives leaner mix by reducing inner venturi pressure same as vacuum leak does.  Dirty air filter gives richer mix.

Thanks guys for the replies. So new story...
Few days ago I took out the gasneedles and I changed the setting so the gasneedles were at their highest. (this was a tip a got from a dutch gs500 board). Okay, next the pilot screws, turned them out. They were almost completely turned out (screw border was at the end of the screw hole.). Motorcycle worked fine, I went for a ride for about 35 km'ers (22 miles).

Everything went fine, I thought the fuel mixture was good now. There were a bit more explosions in my exhaustpipe which is an indicator for a richer mixture. At a certain point when I hold the clutch, the bike dropped very fast in RPM.

I was like, wtf is happening... rode for a few more kilometers but the problem didn't go away. Looked again at my carburators, one of the pilot screws was fallen out because they were turned out almost completely. 
Looked at the spark plugs, they almost changed nothing and the mixture was too lean.

So what do I have to do? Have I done something wrong or do I really need bigger jets? In my opinion i'm afraid i need a bigger jet size to get the ideal mixture. My next question, which size will I need?
And another question, which parts did I lost when the pilot screw fell out?

I hope you guys will help me out with this problem.
Thanks guys!

Quote from: gsJack on July 09, 2015, 10:39:29 AM
Clean air filter gives leaner mix by reducing inner venturi pressure same as vacuum leak does.  Dirty air filter gives richer mix.

How much richer? I don't mean to highjack X's post here, but I'm looking at trying to diagnose a fuel economy issue, have some concern that the PO (once removed, as in PO's PO) may have rejetted the carb. I am only getting 130km on 10L of fuel.


I'm drinking in all the posts even slightly related to carb issues atm 

Quote from: twocool on July 09, 2015, 04:10:11 AM
See...another perfectly good bike is now screwed up!

There is a definite pattern here!  (If you read the 10,000 or so posts of guys who get into "rejetting"....


Cookie

No one fools around with a carb if its working perfectly. In fact is its fine, people rarely even bother doing a pipe or air filter. It usually has a problem, and then there is a desire to mod it, and there is gets worse before getting better ... if it even get better ... or in some cases just get better. Those people don't have multi page posts about how things went haywire.

Quote from: Xasuntox on July 13, 2015, 07:33:22 AM
Thanks guys for the replies. So new story...
Few days ago I took out the gasneedles and I changed the setting so the gasneedles were at their highest. (this was a tip a got from a dutch gs500 board). Okay, next the pilot screws, turned them out. They were almost completely turned out (screw border was at the end of the screw hole.). Motorcycle worked fine, I went for a ride for about 35 km'ers (22 miles).

Everything went fine, I thought the fuel mixture was good now. There were a bit more explosions in my exhaustpipe which is an indicator for a richer mixture. At a certain point when I hold the clutch, the bike dropped very fast in RPM.

I was like, wtf is happening... rode for a few more kilometers but the problem didn't go away. Looked again at my carburators, one of the pilot screws was fallen out because they were turned out almost completely. 
Looked at the spark plugs, they almost changed nothing and the mixture was too lean.

So what do I have to do? Have I done something wrong or do I really need bigger jets? In my opinion i'm afraid i need a bigger jet size to get the ideal mixture. My next question, which size will I need?
And another question, which parts did I lost when the pilot screw fell out?

I hope you guys will help me out with this problem.
Thanks guys!

Have you replaced the air screws You have the spring the washer and O ring on the air screw
If so, OK set to 3 turns out from lightly seated. Then what mains and pilots do you have ? And what set up do you have. That info is needed to steer you in the right direction.

Cool.
Buddha.

Quote from: The Buddha on July 13, 2015, 09:40:25 AM

Quote from: twocool on July 09, 2015, 04:10:11 AM
See...another perfectly good bike is now screwed up!

There is a definite pattern here!  (If you read the 10,000 or so posts of guys who get into "rejetting"....


Cookie

No one fools around with a carb if its working perfectly. In fact is its fine, people rarely even bother doing a pipe or air filter. It usually has a problem, and then there is a desire to mod it, and there is gets worse before getting better ... if it even get better ... or in some cases just get better. Those people don't have multi page posts about how things went haywire.

Quote from: Xasuntox on July 13, 2015, 07:33:22 AM
Thanks guys for the replies. So new story...
Few days ago I took out the gasneedles and I changed the setting so the gasneedles were at their highest. (this was a tip a got from a dutch gs500 board). Okay, next the pilot screws, turned them out. They were almost completely turned out (screw border was at the end of the screw hole.). Motorcycle worked fine, I went for a ride for about 35 km'ers (22 miles).

Everything went fine, I thought the fuel mixture was good now. There were a bit more explosions in my exhaustpipe which is an indicator for a richer mixture. At a certain point when I hold the clutch, the bike dropped very fast in RPM.

I was like, wtf is happening... rode for a few more kilometers but the problem didn't go away. Looked again at my carburators, one of the pilot screws was fallen out because they were turned out almost completely. 
Looked at the spark plugs, they almost changed nothing and the mixture was too lean.

So what do I have to do? Have I done something wrong or do I really need bigger jets? In my opinion i'm afraid i need a bigger jet size to get the ideal mixture. My next question, which size will I need?
And another question, which parts did I lost when the pilot screw fell out?

I hope you guys will help me out with this problem.
Thanks guys!

Have you replaced the air screws You have the spring the washer and O ring on the air screw
If so, OK set to 3 turns out from lightly seated. Then what mains and pilots do you have ? And what set up do you have. That info is needed to steer you in the right direction.

Cool.
Buddha.

First of all thank you for your reply. My setup is a GS500E from 1991 with stock airfilter and a Nikko racing exhaust (just a sporty exhaust). I don't know the standard GS500E jet size, but it is an European (Belgium) bike.
I didn't not replaced the air screws but I lost one pilot screw (and the parts that are going along with it) because it came out when i was riding.

I hope this is enough information to help me.
Thank you!

OK whatever it is that disappeared, You're gonna have to put those back in before you can go further.
Cool.
Buddha.

Quote from: The Buddha on July 14, 2015, 10:46:54 AM
OK whatever it is that disappeared, You're gonna have to put those back in before you can go further.
Cool.
Buddha.

So, everything that disappeared has been putted back in. Which jets do you guys think I'm going to need?

Stock air filter and slip on = 125/40/3 turns/1 washer.
On your bike 125/40 are stock sizes. Please verify. I am working off some blurb I read in a manual 20 years ago. Who knows how many brain cells I have killed off since then.

3 turns  - the air screws you just replaced - set those to 3 turns from lightly seated.
1 washer = needle clip on the middle groove.
Set floats to the top of the bowl. That should do it.

If you see different numbers on the jets = well, let me know what they are, and I'll suggest what you could do.

Cool.
Buddha.

From what I understand the stock GS runs slightly lean at higher revs, what would the correct jetting be for 2000m above sea level? Also at that elevation would running stock jets do any damage on long high speed trips?

The original US spec jetting may work just fine at 5k + feet. Of course at that high altitude you get that wonderful 85 octane ... so 
Cool.
Buddha.

Both my 97 and 02 GSs ran just fine at 5-6k feet completely stock, we spent several days every summer riding out of Maggie Valley into the Smoky Mtns.

Our fuel is 87 & 93 Octane

No biggie really - a handful of jets, some patience and a Dyno should sort things out