Carb problems and holding back

[Vinizio]

Hello guys 'n gals,
Yesterday I picked up an old 1989 GS500E with 26000 kilometers on the clock, this may not be a 100% accurate since they changed the engine with a '94 model. Bike drives well but sometimes she holds in a bit. The previous owner said the gas needles are worn out, so I ordered an used carb to replace it with. The rpm gauges wobbles around a bit and the dash light is bust. Headlight needs a new bulb as well but I think I got a good deal though. Bike shifts like a champ. But my question is if someone expirienced the probs with the holding back as well. And how they solved it. 

Cheers!

[The Buddha]

gas needles are worn out.

Aaaaah, yes, please make sure you also replace the blinker fluid, the original brinker fluid is only good for 150,000 blinks, or 20 yrs, whichever happens first on the 13th tuesday of a leap year if the model year ends in a 9.

Sorry, never seen that happen on a GS, in fact I've seen dirty/no air filters on a desert ridden GS wear out the whole slide, on 1 bike, but never a needle that's worn.
You mean a float needle is not sealing yea possible, but that's a $3 float needle. no need for a whole carb.

I dunno, clean and examine your carb, its likely to be a lot less work than a new and unknown carb, whcih could have a worse worn gas needle (whatever that is).

Cool.
Buddha.

[Watcher]

Can you clarify what you mean by "holding back"?

[Vinizio]

Can you clarify what you mean by "holding back"?

Yeah, well when you pull the throttle half open it stutters and doesn't speed up linear like. It stutters around 2000 rpm 'till like 4000 rpm and then picka up normal acceleration again. Someone told me that the gap where the gas needles go through is a bit worn so the needle will get stuck a bit and forces the bike to accelerate a lot slower than normal. English is not my main language so I hope I made myself a bit clearer.

[Vinizio]

gas needles are worn out.

Aaaaah, yes, please make sure you also replace the blinker fluid, the original brinker fluid is only good for 150,000 blinks, or 20 yrs, whichever happens first on the 13th tuesday of a leap year if the model year ends in a 9.

Sorry, never seen that happen on a GS, in fact I've seen dirty/no air filters on a desert ridden GS wear out the whole slide, on 1 bike, but never a needle that's worn.

You mean a float needle is not sealing yea possible, but that's a $3 float needle. no need for a whole carb.

I dunno, clean and examine your carb, its likely to be a lot less work than a new and unknown carb, whcih could have a worse worn gas needle (whatever that is).



Cool.
Buddha.

Well the previous owner said it wasn't the needle itself, but the gap it goes through. I will take them off and clean them though. See what happens.

[The Buddha]

Can you clarify what you mean by "holding back"?

Yeah, well when you pull the throttle half open it stutters and doesn't speed up linear like. It stutters around 2000 rpm 'till like 4000 rpm and then picka up normal acceleration again. Someone told me that the gap where the gas needles go through is a bit worn so the needle will get stuck a bit and forces the bike to accelerate a lot slower than normal. English is not my main language so I hope I made myself a bit clearer.

This is likely 2 things. Likely both, but fix one and its likely to be mild enough you can retrain your wrist, and not resort to mangling the slide like DJ wants you to.

1. Float is high. This is normal age and wear, the 89-00 floats go high with wear, and likely what that genius was trying to tell you by saying gas needle is worn. Its not, the spring closing the float is bent to allow more fuel, bend it back the other way and correct it.

2. Slide rises too fast. This you train your wrist to not snap it open, just open it fast enough to let the engine be able to catch up.

Needle going through the emulsion tube is just called needle or needle jet. That wearing to the emulsion tube does not happen on a GS, it used to on those pre 89 GSXR's but not a GS. I dunno why, maybe the GSXR needles were more loose in the slide allowing them to wobble more .., but not an issue on a GS.

You may need to nicely set the floats and try it. Now you're likely to be lean, that's cos - well you are, get it rejetted to a 40/125/1 washer/3 turns while you're in the carbs.
Remove the caps on the air screws and jet away.

Cool.
Buddha.

[Kito]

Mine is stuttering until 2k rpm.... Yesterday I clean once again the pilots...

My pilots are #20  .. to be honest, the lettering is quite confusing

seems like 20 to me , besides that squarish symbol.. I may be looking it upside down..



Can anyone tell me the relationship between the number and the hole size ( milimeters )

I would like to check if at some point someone has drilled them.... who knows.

[gsJack]

Can you clarify what you mean by "holding back"?

Yeah, well when you pull the throttle half open it stutters and doesn't speed up linear like. It stutters around 2000 rpm 'till like 4000 rpm and then picka up normal acceleration again. Someone told me that the gap where the gas needles go through is a bit worn so the needle will get stuck a bit and forces the bike to accelerate a lot slower than normal. English is not my main language so I hope I made myself a bit clearer.

Geez guys it's a GS500, rev it up a bit!  I found that a 7000-9000 rpm range gave the best performance in the mountains and ran many hours at those rpm's.  Put 80k miles on my 97 GS and 100k miles on my 02 GS and they were stock all the way.   I found 4k rpm to be the minimum usable rpm on my 97 GS with the 2 circuit carbs but my 02 GS with the 3 circuit carbs would pull smoothly from 3k rpm  Lugging an air cooled mc engine at too low an rpm will do far more damage than running it at higher rpm's.

[The Buddha]

20 is a rejetted pilot size for a 01 and later GS, stock is 17.5, and no we don't drill them, you'd never get it precise enough @ any where near what you need, and 20 is what you need so forget that anyway.
Cool.
Buddha.

[Kito]

20 is a rejetted pilot size for a 01 and later GS, stock is 17.5, and no we don't drill them,

Hey Buddha, I was planning just to check them... My gs is a second hand bike... so I already changed my point of view.. and now believe that anything is possible.

Thanks a lot.

[Kito]

20 is a rejetted pilot size for a 01 and later GS, stock is 17.5, and no we don't drill them,

Hey Buddha, I was planning just to check them... My gs is a second hand bike... so I already changed my point of view.. and now believe that anything is possible.

I am trying to solve this thing on my bike... I wish a smooth delivery of power from 1 up... is annoying to launch the bike needing to rev a little bit...    I may try a pilot larger... I saw some folks using  pilots #40  ( on the gs wiki if I am not mistake)

Thanks a lot.

[The Buddha]

Yeesh dude that 40 pilot is a 89-00 carb rack. 01 on you cant put a 40, 20 is your correct pilot.
oooo wait a sec ... 40 is 89-00 - with a 20 it wont even run.

Look into the mains, if its a 125, you're pretty much spot on for a stock or slip on.

So from there on its just fine adjustments, cleaning and unclogging and ehat not.

I dunno if your carbs are 89-00 now, put pics please.

Cool.
Buddha.

[Kito]

... hmmmm... I am understanding now  the reason people call you Buddha, lol


My gs is a 2004.

Ok, you completely convinced me to stay with my #20 pilots. I cleaned them once more this weekend.. I will try to fine adjust that "awesome"  mixtures screws to see what I achieve once more.

So I will take this chance to extract one more advice from You.

My main jet is 120 (was what i got with my jet gauge accuracy), and after 9k the power drops rapidly.

I was also thinking of going a little larger on the main too. At least this makes sense?



Thanks

[mr72]

There's no need to rev past 9k. Hp peak is around 8k. This is due to limits of the head, valves, etc.  Jetting won't change that.

If you have any problem besides being unfamiliar with the bike, it could be a vacuum leak. They are very common. The jetting is right. You're nor going to change the top end behavior with pilot mixture adjustment, pilot is idle.

[Kito]

Hi Mr 72,

I always try to stay ( when inspired)  between 7k -9k.. the useful engine range (7k torque peak and 9 k power peak).. so I try to shift as close as 9k as possible to fall inside this range again in the upshift.

However, I wish not have a sudden loss of power when eventually passing the 9k.. I was thinking if it could be fuel starvation or as you said project limitations.

Note that I am dealing with two issues... bike stuttering below 2k (now seems to got a bit better after cleaning the jets once more)

And also trying to clarify this 9k up behavior.

[The Buddha]

... hmmmm... I am understanding now  the reason people call you Buddha, lol


My gs is a 2004.

Ok, you completely convinced me to stay with my #20 pilots. I cleaned them once more this weekend.. I will try to fine adjust that "awesome"  mixtures screws to see what I achieve once more.

So I will take this chance to extract one more advice from You.

My main jet is 120 (was what i got with my jet gauge accuracy), and after 9k the power drops rapidly.

I was also thinking of going a little larger on the main too. At least this makes sense?



Thanks

Original mains for a 04 is a 130. You sure you're reading that 120 right You're originally supposed to have 17.5/130 and 60 mids - if it was a US bike.

We jet it to 20/132.5 and leave the 60's alone, we swap the washer from above the needle e-clip to below and set the mix screws to 3.

You may need to rev past 2k when its at a dead stop, but on a rolling slow down and accelerate situation 2k should let it motor along in 1st just fine. You should be able to do that riding @ walking speed without clutch and fits and starts where you rev to 4k and launch only to be in panic as you approach the bumper of the car in front @ breakneck speed, then clutch and brake ... and repeat.
Buddha was due to some weird conspiracy between a few people ~10-12yrs ago.

Cool.
Buddha.

[Kito]

You sure you're reading that 120 right

I will check when I get home.. I am sure that the mid is 60!

However, the mains I am not that sure is they are 120,, and as I said the lettering of the pilot ( I posted a photo here ) is a bit confusing!

Maybe the 04 model here in brazil can be a 03 in US,,, now things are more synchronized, but is not rare to have some delay in what you got and what we get. 
I think this can be related to Einstein's relativity principle of time, maybe!

[mr72]

However, I wish not have a sudden loss of power when eventually passing the 9k.. I was thinking if it could be fuel starvation or as you said project limitations.

It's airflow limitations. Easiest way to overcome that is to get a different motorcycle.

Note that I am dealing with two issues... bike stuttering below 2k (now seems to got a bit better after cleaning the jets once more)

That's probably because it's never running on the pilot circuit. I would first check to be absolutely sure the fuel passageway beneath the pilot jet is clear, and then ensure the air inlet in the little hole in the edge of the throat of the carb is not obstructed, and that air passageway is clear. You can hit my blog and read about how this works and a bunch of other stuff about GS500 carbs (mostly I am talking the Mk1 but it also makes sense for the Mk2 carbs): https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html

In answer to your previous question, and this is why this can be a problem, that pilot jet at size #20 is 0.2 mm opening. That's a very tiny opening. It doesn't take much to obstruct it or clog the passage that feeds fuel to it. Also it doesn't take much of a leak in the pilot needle o-ring for the fuel that's supposed to go to the pilot jet to leak out the pilot needle in the bottom of the carb, which will result in fuel starvation at idle and low revs/light throttle.

And also trying to clarify this 9k up behavior.

It's clear. This is a 2 valve/cylinder head. It can't flow enough air fast enough to sustain >9K for this displacement. The redline is like 10K or higher, that's just because beyond that you risk mechanical damage to the engine, but that doesn't mean it will make power up to those revs. The engine will spin at 11K like on the center stand it just may not make enough power to pull the bike, or not enough to make it worth it to not shift.

In short, you've already found the answer. Shift up after 9K. The bike makes more power at 7.5K in the next gear than it does at 9.5K.

[Kito]

This was a pretty thorough explanation!
I bought the gs a year ago also to learn about bikes mechanics,

Thanks to a lot of grease in my hands, a lot o small issues in my bike, and also because of the help that you guys give....

It has been an intense learning method, and I still have a long way to go!

Tks Mr72 and Buddha!

Clint Eastwood sent applause to you two!

[The Buddha]

Kito and vinizio - sorry I am getting the 2 of you confused.
So kito - your carb seems to be a 01+ and 17.5/60/130 is US spec for it.
Vinizio - you put pics or more details of your carb please.

Cool.
Buddha.