Hi all, I just picked up a GS500F that has been sitting for about 5 or 6 years. I opened the float bowls on the carbs and found the jets were very dirty so I cleaned them out. The bike still runs funny and it makes a strange noise and it definitely sounds like it's coming from the carburetors. It's not really a metallic sound, it just sounds like a fuump, fuump, fuump sound. I will try to get a video up on here when I can so you guys can hear it. The bike does not like when I hold the throttle steady in one position. The RPMs hesitate a lot and it backfires through the carbs. The carbs are in sync but I have not touched the mixture screws yet. I tried to get as much old gas out of the tank as I could and put fresh gas in before starting it up. I checked to make sure the carbs and airbox were seated properly. Any help is appreciated.

did you clean the pilot jets? they are very small and you have to hold them up to a light to verify they are clean. no idea what the noises are. you can spray wd40 on the carbs and inside the boots when reinstalling to help them slide together properly.

Quote from: grader on March 02, 2019, 09:28:47 PM
did you clean the pilot jets? they are very small and you have to hold them up to a light to verify they are clean. no idea what the noises are. you can spray wd40 on the carbs and inside the boots when reinstalling to help them slide together properly.

Yes I did clean the pilot jets. I didn't do a thorough cleaning of the whole carb because I wanted to see if the bike would run first. Nothing else looked terrible though. I have read forums from people with similar running issues and they said that it might be a damaged diaphragm. It kinda makes sense because the noise sounds like it's in the top of the carbs. I guess I'll have to take a look at that. I might decide to just rebuild the carbs. Is that a difficult or expensive thing to do?

Here is a video of the sound: https://youtu.be/qiYF1FeZROE

The revs also fluctuate a lot at idle

if you take the diaphrams out DO NOT spray anything on them, carb cleaners can damage the rubber. i have even had to put them in a freezer to shrink them so they would fit properly (rx1 snowmobile) but i doubt these will be a problem.

Quote from: mrdrprof on March 03, 2019, 11:12:45 AM
Here is a video of the sound: https://youtu.be/qiYF1FeZROE

The revs also fluctuate a lot at idle

Edit: I'm an idiot. The noise was from me not putting the vacuum hose back on the air box haha. It's still not running right though. Sounds like it's misfiring. The spark plugs look good and they have good spark. I'm not sure what it could be

Quote from: grader on March 03, 2019, 12:33:33 PM
if you take the diaphrams out DO NOT spray anything on them, carb cleaners can damage the rubber. i have even had to put them in a freezer to shrink them so they would fit properly (rx1 snowmobile) but i doubt these will be a problem.

The diaphragms look fine. It seems like it might be ignition issue but I'm getting good spark from the plugs and the cylinders have good compression using the unofficial thumb test. I'm not sure what it could be

go back to the jets. remove, soak in CLR, blow out and look through them when held to a light. inside should be clean and round, no crud buildup. pilots can be up sized to #20 from the stock 17.5. when jets are out use carb cleaner in passages in carb bell and blow through using small tube on the can.

Quote from: grader on March 03, 2019, 05:15:11 PM
go back to the jets. remove, soak in CLR, blow out and look through them when held to a light. inside should be clean and round, no crud buildup. pilots can be up sized to #20 from the stock 17.5. when jets are out use carb cleaner in passages in carb bell and blow through using small tube on the can.

Thanks for the advice! I was thinking about going back and cleaning the carbs again because I didn't do a really thorough clean the first time, just enough to see if the bike would start at all. After thinking about it for a little it makes sense that something is probably still gummed up in the carbs after having 5 year old gas sitting in them!

Okay so I cleaned the carbs really good and now she runs perfect! Now all she needs is new tires and she's road worthy!