07 GS500F Idle Issue Update

[tn335]

Update after my initial jet cleaning: So when I had the petcock set to prime, fuel was pouring out of the air box, so it seems like it was crazy flooding which is why it wasn't running well. I disassembled the carb again, found a tiny little brass flake from the jet in the float needle seat. removed it, blew into the line, and sealing great. Put it back together, bike began running without throttle needed, but the idle would kind of jump from 1500, hang out there for 5-10 seconds, then bounce up to 4,000 for 5-10 seconds. At some points it felt like it was going to die but a throttle blip kept it running, but it would push the idle back up to 4,000.

SO it's running now at least, but there still seems to be an issue of some sort. I triple checked that the carb boots were fully seated. Not sure if I maybe missed a vacuum line or something but I am almost certain everything is hooked up right. I'll pull up a diagram and double check. Any other suggestions please let me know.

I regularly ride my bike, put maybe 1500mi on since November. Monday, I rode it up about 80 miles round trip to get some mail from my old house. Drove beautifully, idled beautifully. Filled up about 60/80 of the miles into the ride just to top it off.

Drove home, parked it, went inside, and forgot about it. Went out the next afternoon to start it up. That thing would not fire. I gave it a throttle blip and it fired right up. So I kept the revs up for about 20-30 seconds. we are having a warm front so it was about 65 degrees. and let off. Bike stuttered and died. Tried again, same thing. Went out there a little bit later after taking care of my obligations (glad I have 2 other cars) and came back and just held the revs at 4k for about a minute or two. Still died immediately at idle.

So, I am not sure what's going on. To summarize

• Bike has never given me trouble.
• 80 mile trip,  only thing I did was fill up my tank, but granted it only needed a gallon and a half so it wasn't a full refill.
• Parked the bike, didn't hop back on it for about 20 hours
• Next afternoon, bike will NOT begin firing unless I give it a throttle blip
• Bike will run seemingly normally (it does sound a little burbly but it's always sounded like that), but as soon as I let off the throttle it will stutter and die
• Tried running in PRI on the petcock. no luck. Tried running with fuel tank open, no luck
• Petcock, sparks, and carb was rebuilt prior to my purchase in October

Haven't had too much time to duck around with it, but I wanted to see if there is anything I can check before I pull the carb out. Going to try to get it to my garage without letting it get into idle, but it's 20 minutes and mostly highway cruising, only a couple stop lights.

Any thoughts? Checked the wiki for common troubleshooting, but I couldn't find anything specific to my issue.

Appreciate it.

22,200mi on the bike, so not crazy high miles whatsoever.

I have a lot of automotive mechanic experience, but no experience with motorcycles or carbs.

[chris900f]

Tough call, since it was running well the day before.

It sounds like it may be running on one cylinder. Try starting it, keep it running with throttle, and check to see if both header pipes are heating up equally. If you have a cold pipe, check the sparkplug on that cylinder. If the spark is ok, then it's probably a fuel issue (plugged pilot jet, or water in the fuel come to mind)

[tn335]

Tough call, since it was running well the day before.

It sounds like it may be running on one cylinder. Try starting it, keep it running with throttle, and check to see if both header pipes are heating up equally. If you have a cold pipe, check the sparkplug on that cylinder. If the spark is ok, then it's probably a fuel issue (plugged pilot jet, or water in the fuel come to mind)

Hi Chris,

Yes I took the tank and air box off to check for obvious vac leaks and other noticeable issues. None found. I'm glad I did, because one of my fuel lines were so dry rotted that it tore easily trying to pull it off. Got it replaced, got some line at Advance. Anyway, I thought I found the issue, but I think it may have just been a CA emissions port so it didn't do anything.

I put it back together to check the spark as you mentioned, but both exhaust pipes were an equal temperature after 20-30s of running. I think I'm just going to pull the carbs and go to my garage this afternoon. I'm guessing it just has to be the pilot jet.

Spark on both side, no obvious vacuum leaks found, fuel isn't an issue since it runs under throttle. Can't see much else it could be. Frustrating, but we'll get it done.

So I only topped off with 1.6 gallons that got me completely to full. I did call the gas station as well (It's right outside a FedEx ground terminal) and they said no one had mentioned any issues with it. So, we shall see.

[chris900f]

If your fuel lines were rotted out, a chunk may have made its way into a pilot jet, so that makes sense.

Since you are pulling the carbs, consider removing the welch plugs covering the fuel-adj screws-The stock setting is 3 turns out (close to the limit), a good move is to change the pilots from 17's to 20's and run the adj screws at 2 to 2.5 turns. This gives you some range to fine tune your idle mixture for your local conditions as well as tuning for better off-idle throttle response.

[herennow]

Yes, I'm thinking about something in the carb blocked.

What were you doing with the choke when you try to start?

[tn335]

If your fuel lines were rotted out, a chunk may have made its way into a pilot jet, so that makes sense.

Since you are pulling the carbs, consider removing the welch plugs covering the fuel-adj screws-The stock setting is 3 turns out (close to the limit), a good move is to change the pilots from 17's to 20's and run the adj screws at 2 to 2.5 turns. This gives you some range to fine tune your idle mixture for your local conditions as well as tuning for better off-idle throttle response.

Yes, I'm thinking about something in the carb blocked.

What were you doing with the choke when you try to start?

So here's an update. I pulled the carb and cleaned all the jets. I sprayed some carb cleaner down the passages. I think there was a small block on the "left" carb, because it took a couple bursts of spray to see it shoot out the other side, whereas on the "right" carb, it came out immediately.

I soaked the jets in carb cleaner and could clearly see through all the small holes.

I came home, reassembled the next morning, and it would barely start. I'd have to really try to keep it running but it'd eventually die.

Today, I inspected, and I see that the petcock-carb (vacuum? The line that goes from the outer petcock to the bottom nipple of the carb) line was being pinched pretty bad by the airbox. Going to try to get that corrected tomorrow. Was way too cold today. I am hoping the reason for the struggle to start was simply that line being pinched. I will keep y'all updated.