Hi guys,

I'm new to both the GS500 and this forum so I apologize in advance for sounding like an idiot

The bike that I'm riding is a '94 GS500. My friend bought it from a hobbyist about a year ago, and since my friend is travelling for 4 months right now he's letting me ride the bike. I just got my license last week so this is the perfect opportunity to get more comfortable on a bike.

Because I'm new to riding, the first couple of miles I was just too full of excitement to be critical, but as I ride it a little more often I started noticing some things.

When I rode it for the first time last week, the bike didn't seem too eager to rev. If I was at a constant speed at around 4000 rpm, let's say 30mph in 3rd, and then used full throttle, the bike would struggle to accelerate, I guess I could best describe it as a "stutter". As if the bike was struggling to break through a barrier or something. Apart from making more noise, not much would happen. If I used part throttle though, there were no issues, the bike would steadily accelerate like it was supposed to.

I rode it again earlier this week and it seemed to be better, especially after I opened up the throttle a few times and really rode it at 8000+ rpm for a while. Still the acceleration isn't silky smooth, but miles better than before. I'm hoping the issue resolves itself, but I hope you guys can maybe give me some insight in what's happening with the bike?

The 2nd issue is at the traffic light (only when the bike is warmed up after 25/30 miles). The bike idles nicely, no complaints on that. But as soon as I gradually open the throttle when the lights turn green, the bike almost stalls. It never actually stalls, if you play with the throttle a little the revs will build eventually, but it is concerning me enough to get nervous every time I see a red traffic light coming up 

My friend, the owner of the bike, isn't too technical, but he says these issues weren't there when he rode it last season. The bike was over at the local shop around a month ago. I don't think they did anything major, just clean carburettors, filters, etc.

I should add that the only previous experience I have is riding the CBF500 on which I took lessons. I'm not sure as to how much of the bike's behaviour is due to just having "a different character" than the Honda, but it really feels to me like the bike isn't running at 100%.

I'm not too technical, but I'm eager to learn so I don't mind spending some time working on the bike. I always did most of the maintenance on my 50cc scooter as well, and usually managed to work out everything by myself.

Thanks

UPDATE

Just took it for a ride. At some point the bike actually stalled at the traffic light. Not when I opened the throttle, just while idling.

When I got home I made this video of the bike idling. As you can tell, it's actually not idling so steadily anymore. In the video you can also see the bike dropping revs as soon as I slowly open the throttle.

have you tried playing with different choke settings? is there premium gas in the tank? might be running a little lean.

Quote from: AnonRider on August 10, 2014, 05:35:56 PM
have you tried playing with different choke settings? is there premium gas in the tank? might be running a little lean.

Honestly I never use choke as it starts immediately with the temparatures outside now.

When I rode it last week I heard some pops from the exhaust once or twice, doesn't that indicate it running a little rich? But anyway, is there any easy way of playing with the mixture, without getting new parts?

I just use regular gas. Actually I don't think there's much of a difference between the fuel types here (I'm from The Netherlands).

edit: I've looked around the internet a little more and this sounds exactly like what I'm experiencing:

1) Running rich
symptoms:
-Starts easily in the cold withoput using choke/enricher
-runs well cold but runs more poorly when warm
-hesitation/stumbling at part and/or full throttle
-sooty spark plug
-if very rich, a petrolly smell from the exhaust
-flames etc shooting out of the exhaust
-high fuel consumption
-Running VERY rich will cause the motor to shut down and feels very much like running out of fuel. Thats counterintuitive but there you go.

I understand there's a lot of ways to adjust the mixture, e.g. changing jets, but what would be the easiest way to start playing around?

Quote from: Adam46 on August 11, 2014, 12:23:27 AM

Quote from: AnonRider on August 10, 2014, 05:35:56 PM
have you tried playing with different choke settings? is there premium gas in the tank? might be running a little lean.

Honestly I never use choke as it starts immediately with the temparatures outside now.

When I rode it last week I heard some pops from the exhaust once or twice, doesn't that indicate it running a little rich? But anyway, is there any easy way of playing with the mixture, without getting new parts?

I just use regular gas. Actually I don't think there's much of a difference between the fuel types here (I'm from The Netherlands).

edit: I've looked around the internet a little more and this sounds exactly like what I'm experiencing:

1) Running rich
symptoms:
-Starts easily in the cold withoput using choke/enricher
-runs well cold but runs more poorly when warm
-hesitation/stumbling at part and/or full throttle
-sooty spark plug
-if very rich, a petrolly smell from the exhaust
-flames etc shooting out of the exhaust
-high fuel consumption
-Running VERY rich will cause the motor to shut down and feels very much like running out of fuel. Thats counterintuitive but there you go.

I understand there's a lot of ways to adjust the mixture, e.g. changing jets, but what would be the easiest way to start playing around?

What is the octane rating of your gasoline?  I believe the manual I have recommends 92 octane, so I put premium (93) in.  I would double check this before doing anything serious.

It does sound like you may be running rich.  I can't come close to starting my GS without the choke even in warmer weather. Note: you are not supposed to use throttle to keep it running initially, the manual suggests 30 seconds of choke at about 3500 RPM with no throttle.  You should see if you can do this.  If you're running rich I bet you'll have trouble using the choke as directed.

As for fixing the richness problem I am not qualified to answer.  You can adjust idle mixture via the screw on the bottom of the carbs, but if you're idling at 1200-1300RPM then I wouldn't mess with it (I don't believe it can affect the running circuits, only the idle).

I always question what and if shops did everything they say - not necessarily because they mean to get something over on you, but more because communication isn't always the best from the guy you talk to and the guy that does the actual work...
So, do you know the condition of the air filter?  It almost sounds like a dirty air filter or the filter is too restrictive - what brand/type/model number is it?

The flip side of this which could have similar symptoms is too much fuel - so a simple check of the float height would be beneficial to rule out as well.  This is done by simply attaching a clear tube to the carb bowl drain, set petcock to prime, open drain while bending the tube upward in a U-shape, observe for a minute and ensure the level of gas in the tube is equal to the carb bowl gasket surface.  If its above or below, you have a problem inside the carbs.  Do this for both carbs.

- Bboy

Quote from: DoktoroKiu on August 11, 2014, 10:40:06 AM

Quote from: Adam46 on August 11, 2014, 12:23:27 AM

Quote from: AnonRider on August 10, 2014, 05:35:56 PM
have you tried playing with different choke settings? is there premium gas in the tank? might be running a little lean.

Honestly I never use choke as it starts immediately with the temparatures outside now.

When I rode it last week I heard some pops from the exhaust once or twice, doesn't that indicate it running a little rich? But anyway, is there any easy way of playing with the mixture, without getting new parts?

I just use regular gas. Actually I don't think there's much of a difference between the fuel types here (I'm from The Netherlands).

edit: I've looked around the internet a little more and this sounds exactly like what I'm experiencing:

1) Running rich
symptoms:
-Starts easily in the cold withoput using choke/enricher
-runs well cold but runs more poorly when warm
-hesitation/stumbling at part and/or full throttle
-sooty spark plug
-if very rich, a petrolly smell from the exhaust
-flames etc shooting out of the exhaust
-high fuel consumption
-Running VERY rich will cause the motor to shut down and feels very much like running out of fuel. Thats counterintuitive but there you go.

I understand there's a lot of ways to adjust the mixture, e.g. changing jets, but what would be the easiest way to start playing around?

What is the octane rating of your gasoline?  I believe the manual I have recommends 92 octane, so I put premium (93) in.  I would double check this before doing anything serious.

It does sound like you may be running rich.  I can't come close to starting my GS without the choke even in warmer weather. Note: you are not supposed to use throttle to keep it running initially, the manual suggests 30 seconds of choke at about 3500 RPM with no throttle.  You should see if you can do this.  If you're running rich I bet you'll have trouble using the choke as directed.

As for fixing the richness problem I am not qualified to answer.  You can adjust idle mixture via the screw on the bottom of the carbs, but if you're idling at 1200-1300RPM then I wouldn't mess with it (I don't believe it can affect the running circuits, only the idle).

Over here the pumps offer Euro95 and Euro98, so octane ratings of 95 and 98. I usually go for 95.

Quote from: BockinBboy on August 11, 2014, 10:47:50 AM
I always question what and if shops did everything they say - not necessarily because they mean to get something over on you, but more because communication isn't always the best from the guy you talk to and the guy that does the actual work...
So, do you know the condition of the air filter?  It almost sounds like a dirty air filter or the filter is too restrictive - what brand/type/model number is it?

The flip side of this which could have similar symptoms is too much fuel - so a simple check of the float height would be beneficial to rule out as well.  This is done by simply attaching a clear tube to the carb bowl drain, set petcock to prime, open drain while bending the tube upward in a U-shape, observe for a minute and ensure the level of gas in the tube is equal to the carb bowl gasket surface.  If its above or below, you have a problem inside the carbs.  Do this for both carbs.

- Bboy

When it was at the shop a couple of weeks ago my friend was still riding it, so I don't know the specifics of what was done to the bike.

Thanks for your advice, I'll start checking those things over the next few days.

To get a better indication of whether the bike is indeed running rich, I checked the plugs.




Honestly I don't know how old these are, but to me it seems like they need to be replaced?

yikes