couple of issues with a GS500

[73ch13]

Hey all... I'm a newbie rider and newbie wrenchmonkey, please be gentle. I just started riding and I have a 2007 Suzuki GS500F with under 10k miles that I bought last year used, from a dealer. First bike. I've changed the oil, lubed the chain for this season. I just noticed a couple of things.
1. On cold starts, with the choke on, the bike will start fine. I shut off the choke after about 30 seconds and the bike will idle fine at about 1200 RPM, except I'll hear popping every once in a while. The popping will be followed by a puff of white smoke coming out the exhaust which stops soon afterwards.
2. After warming up properly and riding for about an hour or so, I notice that at stop signs/lights, the engine hangs at about 3000 RPM and will not come down to the normal idle.
I have checked the choke cable and throttle cable, both seem to be fine. I took the fuel tank and the air filter off the bike and started it. I noticed the popping I mentioned above happens in the air box. It looks like something is blowing back from the carbs into the air box. I think it's gasoline. I'm attaching a pic with the area from where the blow back occurs. The pic is of the right carb viewed through the air box. I'm not quite sure what I'm looking at as far as what those ports are for. Any suggestions?

[Motorcycle Forum]

[Easy Rider]

1) lubed the chain for this season.

2. After warming up properly and riding for about an hour or so, I notice that at stop signs/lights, the bike hangs at about 3000 RPM and will not come down to the normal idle.

1) Lube'ing the chain is NOT a once per season operation. It needs a little shot every few hundred miles or so.

2) Have you tried to adjust the idle speed when the engine is hot and it's running about 3K ??

The idle speed should be set with the engine hot. That will probably mean that you will need to keep the choke partially ON for much longer as it warms up.

If the idle speed adjustment has no effect at that point, then there is a problem that needs to be fixed.

A healthy dose of carb cleaner in the gas would be a good idea. I like Berrymans B12 Chemtool.

It's possible that your float level is too high........or that you have a vacume leak around the carb boots......but you should take a shot at the easiest and cheapest and most common things first.

[73ch13]

Thanks! Things I needed to know. Without using a vacuum tool, is there any way to check for vacuum leaks?

[Easy Rider]

Thanks! Things I needed to know. Without using a vacuum tool, is there any way to check for vacuum leaks?

With all the stock equipment in place, you carefully squirt a LITTLE bit of carb cleaner or starting fluid or even propane around the boots ahead of and behind the carbs........and listen for RPM changes. If it's bad enough to cause what you are describing, just a close inspection might turn up something loose or cracked.

[slozomby]

more on chain: lube every couple of weeks or few hundred miles. whichever comes 1st.

[73ch13]

Thanks everyone. Much appreciated!

[73ch13]

With all the stock equipment in place, you carefully squirt a LITTLE bit of carb cleaner or starting fluid or even propane around the boots ahead of and behind the carbs........and listen for RPM changes. If it's bad enough to cause what you are describing, just a close inspection might turn up something loose or cracked.

On the air intake side and the opposite side?

[Easy Rider]

On the air intake side and the opposite side?

Anywhere there could be a leak.
On the boot between air box and carb.........on the gasket or boot between carb and engine......and around any vacume hoses, like one going to an automatic p e t c o c k.

You seem to have homed in on the vacume leak thing but it is maybe more important that you check the other things in my first post.......like does the idle speed screw DO ANYTHING when the engine speed is high.

Also, is it possible that the "choke" is working it's way to partly ON from the vibration of riding ??

[73ch13]

Anywhere there could be a leak.
On the boot between air box and carb.........on the gasket or boot between carb and engine......and around any vacume hoses, like one going to an automatic p e t c o c k.

You seem to have homed in on the vacume leak thing but it is maybe more important that you check the other things in my first post.......like does the idle speed screw DO ANYTHING when the engine speed is high.

Also, is it possible that the "choke" is working it's way to partly ON from the vibration of riding ??

Easy Rider, I did sorta home in on the vacuum leak. I can't tell whether or not the choke is working itself into the on position. I checked the movement on the choke and it seems fine. As for the idle speed screw, I checked it when the RPM was hanging at 3000. Turning it in either direction causes the RPM to drop back to normal. Almost burned my hands doing that! But what's it all mean?

Yet again, all the help/advice is highly appreciated.

[Easy Rider]

Turning it in either direction causes the RPM to drop back to normal. Almost burned my hands doing that! But what's it all mean?

Are you sure that you are talking about the idle speed stop mechanism......which is usually easily accessible in an area that is not dangerous to your skin.......or the idle air mixture screw ?? (although I'm not familiar with that model bike).

Anyhow.....that is sounding more like there is a mechanical binding somewhere.
Spraying the outside of the carbs and mechanisms with carb cleaner might be a good idea, as well as inspecting the cables and external connections. Sometimes the butterflys in the throat can stick too.....so a good shot of spray cleaner down the throats might be a good idea too. You can check the choke by pushing it toward OFF when the problem is occurring.

And finally, whatever is causing this will probably turn out to be something rather simple and a shop visit probably wouldn't be very expensive. I'd encourage you not to ride it much until it's fixed though. Things like that can put you down if your attention strays for just a second at the wrong time.

[krishnkhanna]

Hey, I know its late in the year. Hopefully you havent put your bike away for the winter yet. But I am going to post anyways for you or others who are having this problem... Bottom Line: I think its a cracked intake manifold.

I had the exact same problem. Literally. Except my popping got to the point where one of the cylinders was firing. My bike had started running at half the normal idle and lost half of its power. I would have to rev it to 6K just to be able to get it to move from standing. And it was smoking up a ton!!! People would honk at me because it was smoking so bad.

I cleaned the carb like 4 times, cuz I knew it had to be a air fuel problem. I had heard that popping is a sign of your engine running lean. Which made sense... But the smoke meant there was uncombusted fuel being expelled which is a sign of your engine running rich... Every time I opened it up, the left side would have fuel caked onto it. A thin yellow film. And it was obviously the side that wasn't working. I would clean it up. Check and fix the float heights, and reassemble. It would work well for a day or two, and then the same problem would return. After 5 months of this %%%%, I was so frustrated, I was about to sell my bike. But decided to take it to the shop instead, even though I couldn't afford it.

Turns out I was right. It was a fuel air problem. But not in the carb. THE INTAKE MANIFOLD HAD CRACKED!!!! Its the part that connects the carb to the engine. It had cracked on the left side (the side I knew was giving me problems)... SO every time, I would take the carb out, I would increase the size of the crack and make it a little bit worse. More and more air would go into the cylinder (causing the popping and lean running), until it got so bad that the cylinder stopped firing, making the bike run like %%%% and smoke up to the max. The shop put a ton of silicone on the manifold and it fixed it temporarily. I bought some new manifolds (they are like 20 bucks a piece on Bike bandit). Installed them with some silicone sealant (but the stuff that is rated for automotive use-- it gets pretty hot in that area of the bike) and everything works like a charm!!!

I looked for hours on forums for these symptoms and found nothing. Had to dish out $100 for the labor at the shop. But its worth it.

Vayo Con Dios Brah