Surging and Choke?

[Gbarnes]

I have had my 1989 Gs500E for about 2 years now and I have been trying to get this thing running and driving for the entire time. I even took it to a shop and had them rebuild and sync the carbs and adjust the valves along with a new ignition coil installed.

So here is the skinny on it, It starts up and runs fine for a short ride then it starts to surge and try to die, it will idle at about 800 rpm I have it set to idle at about 1300 when warm. I can pull off the road and throw the choke on and it idles up I turn it off after a minute or so its idling at 1300 smooth not hunting for idle or surging, then we are all good for the ride back. The case doesn't get to cold or anything along those lines and I just can't seem to get it to work right.

suggestions would be great because no one seems to know what is going on with it.

[Jonny Boy]

Try blipping the throttle in neutral when it plays up and see what happens, iirc hanging revs that take a few seconds to drop down indicates a lean condition and revs bogging before going up means it's rich. If it's lean you could have air leaks. Cracked intake boots or bad intake o rings are a classic cause.

[mr72]

Try blipping the throttle in neutral when it plays up and see what happens, iirc hanging revs that take a few seconds to drop down indicates a lean condition and revs bogging before going up means it's rich.

Good old internet myth pops up again.

If the revs hang it means the idle is set too high. If it dips it means idle is set too low. Now, you might have set the idle too high because it's lean and won't idle otherwise, in which case it's not really idling, and that's why it surges. It's pulling fuel out of the main jet with a very small throttle opening so the airflow is inconsistent and therefore the "idle" will be inconsistent.

I have had my 1989 Gs500E for about 2 years now and I have been trying to get this thing running and driving for the entire time. I even took it to a shop and had them rebuild and sync the carbs and adjust the valves along with a new ignition coil installed.

So here is the skinny on it, It starts up and runs fine for a short ride then it starts to surge and try to die, it will idle at about 800 rpm I have it set to idle at about 1300 when warm. I can pull off the road and throw the choke on and it idles up I turn it off after a minute or so its idling at 1300 smooth not hunting for idle or surging, then we are all good for the ride back. The case doesn't get to cold or anything along those lines and I just can't seem to get it to work right.

suggestions would be great because no one seems to know what is going on with it.

Read the link in my signature.

In short, there is at least two, maybe three problems.

1. the idle is set too fast. It should idle at more like 1100 rpm when it's warm.
2. you are turning the choke all the way off before it's warmed up enough, that's why it stalls and idles low after you run it for a few minutes. It really takes like 5 minutes or more of actual running through the gears to get it warm enough to come fully off the choke.
3. maybe: when the shop rebuilt the carbs they either didn't change the pilot jets or put stock 37.5 pilot jets in the carbs, so your idle mixture is going to be lean no matter what you do. You will probably wind up setting the idle too high to compensate. Pull the carbs and put in 40 pilot jets. Then set the idle speed and mixture as instructed in my blog post in my signature.

[Gbarnes]

Thanks for the advice I will drop the idle down but as far as kicking the choke off early it had been warming up for about 10 minutes. I don't want to over heat it. But I will give it a go thanks for the advice.

[mr72]

IDK what you mean about warming it up for 10 minutes. You mean sitting on the side stand running? Or actually running through the gears and revving?

It's not going to overheat on choke. It's not going to overheat riding on the road on choke or not. I've ridden my old GS a lot in 100F+ central Texas summer and never had a hint of it overheating. Don't worry about that.

There's a section in my blog post about startup and running procedure, but I'll post it here just as an FYI:

Step 1 (if the bike has been sitting for an hour or more): turn the choke all the way on, pull the clutch in (or put in neutral), turn on the key, and push the start button. The bike should start with full choke and no throttle and within moments it should rev up to 4,000 or 5,000 rpm. This is normal. Let it run like this for a minute or two while you put on your helmet and gloves.
Step 2: Ride the bike away and reduce the choke to maybe 1/2. If you turn the choke all the way off while the engine is still cold, it may stall when you try to let it idle, such as when coming to a stop. So don't turn the choke all the way off.
Step 3: After riding for about 5 minutes, the bike should idle with no choke. You can turn off the choke. It will idle lower than normal but probably will not die. It is not fully warmed up.
Step 4: After riding about 15-20 minutes on the road, that is going through gears etc., the bike will be fully warmed up. Now you can assess the idle speed and mixture, but not before.

If it doesn't behave like this^^, then something is wrong. There are lots of things to go wrong, again, read the blog post, it'll probably get you sorted, especially if your bike is stock (airbox, exhaust, jetting, etc.).

[sledge]

Can I point out (assuming the carbs are originals) are now 33 years old and well past their `best before` date.

You need to carefully check the slides, slide guides and emulsion tubes for wear before anything else!

You can fiddle with the settings and the jets as much as you like but if these parts are worn stop right there......... anything else is a waste of time and effort !!!

[herennow]

A nice old suzi!!! Post pictures!!!

[gag.]

Hello buddy


Sent from my iPhone using Tapatalk

[sledge]

A brief article that outlines the wear problems that Mikuni slides are prone to and how to identify it.

The internet is full of articles on how to rebuild GS500 carbs but very very few mention the slides and emulsion tubes.

https://store.moto-lab.com/articles/bst36-slide-guide-wear-indicators

[Jonny Boy]

Try blipping the throttle in neutral when it plays up and see what happens, iirc hanging revs that take a few seconds to drop down indicates a lean condition and revs bogging before going up means it's rich.

Good old internet myth pops up again.

It's in the GS Twins Wiki on rejetting so perhaps needs removing if the myth is incorrect.

[sledge]

Good carb men are few and far between.

You need a lot, and I mean a LOT of.........not just knowledge. but also experience to diagnose and rectify carb issues, especially if the carbs in question are not in front of you to examine and if you are going to overhaul/rebuild yours you need to look at and consider EVERYTHING contained within them.