Hello everyone,
(I am from the Netherlands, hence why I include km/hr)

Since a 2-3 weeks ago I can say that I'm a proud owner of a Suzuki gs500 

The previous owner did not do alto of maintenance so I already bought new oil,oil filter, new rear brake pads, chain cleaner and lube. The plan is to do the maintenance for these parts tomarrow.

A little about my situation.
I don't go on the highway often but today I had to drive 41miles(66km) for a date. The drive went fine, tried to see how far the bike would go, reaching 100mph(150km/hr) at one point but didn't feel safe to go faster at that time. So I was almost there when my tank started to become empty and I had to switch to the reserve. That's where I experienced problem nr1. The bike wouldn't start. I also used the chose, started it but when I went into first gear it died again. I let it sit for a few min before trying again. It worked!! but I could feel that it didn't had the same acceleration as before(it also felt weird)I drove to a gas station, filled her up and the problem went away.

I got to my date, had a amazing time and went on my way to get back home.
So I was driving 80mph (130km/hr) and I had to overtake a truck so I went 93mph (150km/hr) and after I was done overtaking the truck I noticed I was losing speed. So I tried to give her more gas but still losing speed. It went down and down, but the engine was still running. I reduced the throttle and could feel a little pull, so I increased more.

I later realized that once I gave her a certain amount of throttle, when I go over that point it feels like she gets 0 fuel and start to decline in speed again. But if I keep it at the amount before it starts to not get any fuel I get a max speed of 75mph (120km/hr)

When I got off the highway everything went fine, first gear felt normal, second gear felt normal, all the gears felt normal. Just at around the 60mph (100km/hr) mark it start to have the problem. It would still go up to about 70mph but very slowly and steady.

So I decided to do a little test. I went in second gear (and I know it's not so good for the engine) and I pulled the throttle wide open and again at a certain amount I felt like the engine did not receive any gas.

I hope you guys/girls know what's wrong and thank you in advance for taking the time to ready

doeplidoep


PS. It's like I get no throttle response at a certain amount of throttle if that makes sence.

Hello everyone, a little update comming through.

So, I went to a parkinglot to do some troubleshooting and (while googling i read that some people have problems with the petcock) so I tried both positions but same result with both positions.

It's like when i pull the throttle, I get to a certain point where my rpms still increase but the speed goes up very slowely. If i'm in neutral and go WOT or atleast high throttle I can hear the engine revving very hard. But when i ride and i get to a certain amount of throttle my bike decides to just give me very little gas. Not the amount i want but the amount to go a little bit faster.

My only thought could be that either there is something wrong with the throttle cable or maybe when I give it the amount of throttle that one carb decides to not do it and let the other one do all the work.

Now that I think about it the second option could make sense because when I open her up to a certain point i still get speed increase but extreamly slowely but when i go over that throttle point she actuelly decreases i  speed.

Honestly I have no clue but maybe this update can help pinpoint the problem a little bit.

Thank you for reading.

Doeplidoep

Sounds like you may have a plugged filter that's not letting enough fuel to flow to keep up with demand.  This would get worse when the tank is empty since we rely on gravity to push fuel to the carbs.  If you have an inline filter, change it.  If you don't have an inline filter, there's a screen on the fuel pickup in the tank that may be plugged up.  You'll have to take the tank off and then the valve assembly comes off with two screws.  The screen is just a press fit onto the fuel pick up, replacements are just a few bucks on ebay and sometimes come with a new gasket.

There are other things that could cause what you describe, but fuel supply seems the most likely (to me).

Clogged or sticking float needle valve is also something to check. Although I'm having trouble following precisely what is happening.

hello, and welcome to the forum, and merry Xmas😉

the GS is not a very powerful bike, so comparing throttle response in neutral is very different to when the little engine is trying to move the large motorcycle.

It also seems to me as though you are suffering fuel starvation. This can be to the three causes already stated;
carburettor float level is too low,
or else a blocked vent in your fuel tank cap,
or a dodgy petcock.

First test is to run with petcock on Prime. If problem goes away check petcock and/or vacuum hose.

If problem is still there, a good test is to attach a length of clear hose over the carb drain and end into a bottle that is hard to knock over. Take all precautions - highly flammable.
If you open the carb drain, you should get around a cup, 250cc, of fuel per minute from a single carb.  If not there is a blockage such as in the tank cap or float fuel level too low.
Good luck.

Quote from: herennow on December 26, 2018, 01:41:57 AM
If problem is still there, a good test is to attach a length of clear hose over the carb drain and end into a bottle that is hard to knock over. Take all precautions - highly flammable.
If you open the carb drain, you should get around a cup, 250cc, of fuel per minute from a single carb.  If not there is a blockage such as in the tank cap or float fuel level too low.
Good luck.

Great tip there, thanks!  I'd suggest doing it on a near empty tank so you don't have the mass of fuel pushing it through a minor blockage.  It'll also have to be done with the fuel chicken on Prime or some vacuum applied to test in the normal position.

I would be looking towards a clogged fuel system as well, but as an alternative if it only happens at higher speeds and not when stationary it could be that your breather tubes are missing or in the wind.

Often wind passing over the open end of some of the breathers, namely the carb breather, can cause weird fuel delivery issues.  By factory most of the breathers are routed to terminate behind the air box where they are open to the atmosphere but also protected from the wind.

A hose routing diagram should be easy to find.

The floats are suspect.

If they're ok then see if the breather tube is OK.

Floats first.

Thank you all for your replies.

Sadly i did not read them before working on my bike and I would advise you to prepare yourself cuz you're gonna hear some stupid shaZam!.

Okay so, all I could think of was some sort of restriction somewhere. Something that did not allow my engine to get the fuel it needed when I opened the throttle so I worked my way towards the carbs. While doing this we unscrewed the wrong screw on the throttle cable. Yeah, I know what you're thinking. The bike now runs like shaZam!....

We did get to the carb and it was clean, really nice and clean. The only problem I could see is that one of the jets. (the one that's hidden in the tube) had a torn head, aka I couldn't get it out. But besides all of that the carb was clean, no problem with the floaters.

I called the repairman and they told me to get it fixed will properly cost me close to 1000 and I bought the bike for 1000 so there is no way I'm going to do that. So my plan is to figure out how to fix the throttle part so I can at least ride the bike around town and than work my way to doing the things you guys are recommanding me to do.

Pretty much if I ride the bike now, I don't only hear weird noises it also stalls without the choke on when I stop. -.-

Thank you again for the replies


This might be a clear way of describing the initial problem

I open my throttle to lets say 30% and if I open it more, I still get slow RPM/speed increase but I don't feel the pull you would feel when opening the throttle more. So I can for exemple get to 80km/h but than if I open her up more it can even happen that it actuelly declines in speed.

PS
Is the prime ON position when the arrow is pointing down?

Yeah, this is what I was afraid of, I was misunderstanding the description.

It sounds like you have two issues:

1. some carb problem, could be a half dozen things and likely more than one. I recommend doing the procedure outlined in my blog to get to a correct starting point rather than trying to diagnose issues that may have multiple causes.
https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html

2. clutch adjustment issue, in this case not enough free play. You need to do the 3-point clutch adjustment outlined here: http://wiki.gstwins.com/index.php?n=Maintenance.FrontSproketCoverRemoval ... this will likely fix the issue you are describing as, when accelerating at high speeds, the engine revs but the bike doesn't gain speed.

Good luck.

mr72,

do you by any chance also have a guide on how to fix your throttle cable on your carb? how to tune it correctly. Or is that just a case of trial and error until the bike runs correctly?

thank you for your quick respons

I don't know what you mean about "tune throttle cable". On my GS there is just one throttle cable, and adjusting for 2-5mm of free play is pretty easy and intuitive to do.

I'm talking about the cable on the carbs that make the valves in the carb open and close
(sorry, I don't know the correct name for all these parts)

Are you perhaps referring to the idle screw (big knob between the carbs that raises and lowers the butterfly valve to increase or decrease idle RPM)?

Quote from: doeplidoep on December 28, 2018, 07:50:29 AM
I was refering to the cable that goes from the throttle to fhe carbs.

You see, we opened up the carbs but in order to do tgat we had to detatch the throttle cable on the carbs, we did that but we unscrewed the longer screw on there so  now the throttle is messed up. What I mean by that is that now when I run the bike it not only makes weird noises it also stalls alot without choke while that before nevrr happend.

Hi, dpd, are you attacking this work with a manual or are you going in blind?

Quote from: herennow on December 29, 2018, 12:53:49 AM
Hi, dpd, are you attacking this work with a manual or are you going in blind?

Half, at the time I was using this video: https://www.youtube.com/watch?v=AJh1hxNf7BA + the digital manual. I figured that this did not work for me and I ordered the manual.

In the video on 5:50 I by mistake unscrewed the barrel adjuster(the one that determines the slack on the cable). I'm not sure but I think the nut on the throttle does the same thing. Anyways mr72 already gave me a good description on how to fix that small fuckup.

Quote from: mr72 on December 27, 2018, 08:17:46 AM
I'm not sure what year your GS is or whether this applies. If you have a Mk1 (pre-2000) GS500 then it's just a matter of attaching the cable and adjusting the lock nut which IIRC is a 10mm. First turn the barrel adjuster at the handlebar all the way in so there is the maximum amount of slack. Then loosen the lock nut at the carb on the cable adjuster and adjust until there is >5mm or so of slack in the cable when you turn the throttle, then tighten the lock nut. You can then turn the barrel adjuster at the handlebar out until you get the free play correct, about 2-5mm. Depending on your handlebars and cable routing etc. more slack may be required to keep it from pulling the throttle when you turn the handlebar.

and I read his blog.
So what I think I need to do after I get the throttle cable in correctly with freeplay doing the "first time running and adjustment" he mentioned in his blogpost.

After I get this to work correctly, I will go back to the initial problem and stay away from the carbs.

I don't have a garage or a indoor place to work on my bike and was working outside, I postponed my work on the bike until after newyear because 1. I don't feel safe working on the bike while kids are playing with fireworks (don't feel like going kaboom) 2. I am waiting for the manual to arrive.

EDIT: It will take 3-4 weeks for my manual to arrive but I will be leaving for a long internship starting februari, so I decided that I will work on the bike in the mornings when there are no fireworks going on and continue next year aswell

Hello everyone, so I worked on the bike this morning to fix the small issue I had and it now runs pretty decent. This time I also made pictures to tell what is did.
I opened up the bike and went straight for the throttle cable on the carb. The screw holding the cable was loose so I first adjusted it until the cable had >5mm of freeplay and than tightened it up again. I checked the freeplay on the throttle and turned the handlebars both ways to look if that would move the cable. It did not. I put everything back together but ofc forgot to open the valve below the fuel tank -.-


Now it was time to go for a ride.
Previously I never had to play with the choke. Now I have to so that was a little bit new.
I started the bike, it ran for approx, 60sec before dying so I started it again with full choke. After a few seconds it revved up to 5-6k RPM.
After letting it run for a little less than 30 sec on full choke, I did half choke and let it sit at around 3k rpm for around 1,5 minutes.
Now it was time to actually start riding, I drove on it with half choke but noticed I had to increase it while waiting at stop lights.
After driving around with half choke I got to the point were I was able to turn off the choke completely and idle at around 1300rpm, later when I got home I adjusted the idle speed screw until the RPM was around 1100. I was not able to adjust the idle mixture yet because I first have to look around the house for a screwdriver that is small and fits in the hole were the mixture screw is hiding.
I did notice that even tho I have to use the choke now until I drive for around 15-20min to warm up that the bike makes less weird noises, before when I shifted I would hear weird noises (hard to describe what exactly)


I did notice that I gave multiple confusing descriptions of the main problem. I used the time of riding around to figure out what exactly is going on so that I can give a good description
first, second and third gear absolutely no problem. I can accelerate pretty good.
I don't think there is a problem with 4th gear, at least I did not notice anything.
Only when I get on the highway in 5th gear, and I speed up to around 110-120km/hr(depending on wind) when I get to 6000 RPM it does not matter how far I open the throttle, I get no RPM increase, no speed increase. It does feel weird. It feels like the bike wants to go but cant. I can actually feel it going forward but than backwards if that make sense. (like its bouncing forward but than realises it cant and goes back and than tries again)
Than after I decrease the throttle to a certain amount I can feel the loss in power and increase when I open her up a little bit more. But when I go over a certain point it feels like I hit a wall in the RPM/speed aspect

petcock position while running

This means that it is on ON position right?

I did try and shift down to 4Th gear but same thing, once I get to  a certain point it feels like I hit a wall and cannot accelerate more.

i hope this description is better.

Thank you all for reading, and thank you alot for giving tips and advice, it really helps alot!

doepidoep

That sounds like one of the various fuel delivery issues others have mentioned here.

1. slide is not coming up in the carbs due to manifold vacuum leak somewhere
2. float level is low or float needle valve sticking shut
3. fuel delivery problem between tank and carbs, like petcock not working right or clogged/collapsing lines

Bike should exceed 120kph quite easily especially in 3rd or 4th gear.

Are you sure it's not a beginner's bike that has been throttled to keep it to 25 kW (or whatever it is) in Europe?  Normally a plate in the carb.
Also is filter clean and unblocked? This symptom could be a blocked air filter.

Also,did you check the sizes of the jets while you were in the carbs? If someone put in a ridiculously large main jet, this could also lead to the affect you describe...

Did you get a Haynes manual or a factory one? Factory manuals are usually for "trained technicians" and they leave out lots of stuff you should have learner in your training. Not to say it's not usefully but it can be tricky if it's your first time wrenching.