Hi, good evening. This is my first post here and wanted to say hello.

I picked up an 05 for a good deal. I'm currently trying to get it running properly and have an issue with the right cylinder. I cleaned the carbs and put in a new petcock rebuild kit and new valve and seat as they were really gummed up. I started the bike and it is only running with the left cylinder. Right carb is still seeping a little too. It starts with the choke on but will on idle on one cylinder. I guess I'll pull the carbs again. I'll check for spark on the right cylinder on the weekend. Jets were cleaned too. Maybe that cylinder is not getting fuel? It sounds noisy running on one cylinder, it's that how it sounds with only one firing? Thanks

Check for spark first so we can rule that out.

Quote from: Bluesmudge on October 20, 2021, 09:31:03 PM
Check for spark first so we can rule that out.

On the 04+ you'd lose spark in both if there was an issue, but I dont know what auxillary ground getting iffy would do cos I never had a 04+.
Cool.
Buddha.

Ok, so I have spark. I also noticed the plug was very loose, was able to screw it out by hand. Have not tried to start it as I got called away, will try later. Thanks

Ok, good spark, good compression, new spark plugs, new needle and seat. I can't seem to get the right cylinder to fire. I pulled the carbs off again to check pilot jet for blockage and took all the jets out in that carb and used a guitar string to clean to make sure. It's not getting fuel into the cylinder? A squirt of starting fluid will for a brief fire. Hmmm?

The right cyl in an 04+ has vacuum feed. If the rest is all perfect, you might have a vacuum line leak.
Cool.
Buddha.

Quote from: The Buddha on October 24, 2021, 11:16:37 PM
The right cyl in an 04+ has vacuum feed. If the rest is all perfect, you might have a vacuum line leak.
Cool.
Buddha.

Would running it on prime might bypass any vacuum issues? Thanks

Running it on PRI will identify fuel delivery issues that are due to no vacuum at the petcock. But that won't fix the vacuum leak at the carb that Buddha is talking about.

If there is a vacuum leak, it won't run right. Period. Buddha was pointing out a common cause of vacuum leaks. Poor fuel delivery would be an effect of this vacuum leak, not a cause.

Sometimes you can check for a vacuum leak by spraying aerosol around the carburetors. It may suck in the aerosol (like WD40) through the vaccum leak and you will hear the engine run differently. However, just because that test doesn't do anything doesn't mean there isn't a vacuum leak, it may be too small of a leak for that test to work.

Sometimes the best fix is just the replace any potential cause of vaccuum leak rather than trying to find the exact part with an issue. That is, replace any rubber part/o-ring between the airbox and the engine's intake. Airbox boots, carb o-rings, vacuum hoses, intake boots, intake boot o-rings.

Buddha, is the vacuum source for the '04+ carbs you are talking about a vacuum line? Does it get vacuum off the intake somewhere? I should know this since I have '06 carbs but I haven't messed with them in a long time. Are you talking about the caps on the top? Because I thought those just change the needle position somehow to lean out the mixture...pretty sure you can cap them off and everything still works.

Quote from: Bluesmudge on October 25, 2021, 03:39:48 PM
Sometimes you can check for a vacuum leak by spraying aerosol around the carburetors. It may suck in the aerosol (like WD40) through the vaccum leak and you will hear the engine run differently. However, just because that test doesn't do anything doesn't mean there isn't a vacuum leak, it may be too small of a leak for that test to work.

Sometimes the best fix is just the replace any potential cause of vaccuum leak rather than trying to find the exact part with an issue. That is, replace any rubber part/o-ring between the airbox and the engine's intake. Airbox boots, carb o-rings, vacuum hoses, intake boots, intake boot o-rings.

Buddha, is the vacuum source for the '04+ carbs you are talking about a vacuum line? Does it get vacuum off the intake somewhere? I should know this since I have '06 carbs but I haven't messed with them in a long time. Are you talking about the caps on the top? Because I thought those just change the needle position somehow to lean out the mixture...pretty sure you can cap them off and everything still works.

Can I just cap it off on the intake and use pri as my on/off instead of the complicated vacuum system?

The vacuum system isn't complicated. If you cap it you will be left with no reserve and probably flooded carbs and puddles of fuel from time to time.

Replacing vacuum hoses and o rings is not complicated or expensive. Not worth skipping.

Quote from: mr72 on October 25, 2021, 06:16:51 PM
The vacuum system isn't complicated. If you cap it you will be left with no reserve and probably flooded carbs and puddles of fuel from time to time.

Replacing vacuum hoses and o rings is not complicated or expensive. Not worth skipping.

Haha, don't want that, thx 😊

Out of curiosity, how did you know that it was running on only one cylinder?

Quote from: mentalshark on October 25, 2021, 10:02:37 PM
Out of curiosity, how did you know that it was running on only one cylinder?

I could just tell as it was running rough. Pulled off the the plug cap and no change.

Well, of course, check the spark on the dead cylinder. But most likely the pilot jet is clogged on that cylinder. Shoulda replaced them while the carbs were off if you didn't. Along with ALL of the o-rings. Just saying. That's a lot of work just go get the carbs off, should do everything you can to proactively fix IMHO.

If it is only running on one cylinder at idle, then it will take huge idle speed settings to just barely start, will run on choke when cold only at like 1.5k-2k rpm and will stall under any kind of load, like trying to ride it. If it's a clogged pilot jet only, then it should wake up and run on both cylinders when you wack the throttle open and let it rev above like 5K.

I would check:

1. is there spark on both cylinders? rule out ignition.
2. is there fuel in the right float bowl? You can also check the float height while you are at it by using clear tubing on the drain hose. But if no fuel drains out, that will tell the tale.

And when you determine "yes" to both of these answers, then pull the carbs back off and do a proper full rebuild and replace the intake boot o-rings while it's all apart along with the petcock vacuum hose and all the rest of the vacuum hoses.

Link in my signature for some step by step help, altho it's geared towards the '89-00 carbs so you'll have to make mental adjustments.

Quote from: mr72 on October 25, 2021, 06:16:51 PM
The vacuum system isn't complicated. If you cap it you will be left with no reserve and probably flooded carbs and puddles of fuel from time to time.

Replacing vacuum hoses and o rings is not complicated or expensive. Not worth skipping.

Lots of good advice mr72, but the vacuum system is pretty complicated on the '04+ carbs as Suzuki was trying hard to shoehorn the incredibly polluting GS500 engine into the 2006 - 2009 US emissions standard. There are vacuum lines and "Ts" going everywhere for emissions stuff. The Throttle position sensor, those weird vacuum controlled needle caps, another black box thing...I'v never known what it all did. I just removed it all and capped everything off, unplugged the TPS, and it seems to work fine...I did that because otherwise its too many unknown variables to troubleshoot the carb for a mere mortal. Like you said, you need the vacuum line to the Petcock but the other vacuum stuff is a bit of an unknown and with so many connections there are a ton of potential failure points.

Trollywire, you may want to do what I did and try to make the '04+ carbs resemble the '01 - '02 carbs by removing as much as possible. When you are done it should just be a fuel line and a vacuum line (that goes to the petcock) connected to the carb with everything else capped off. You will have removed a spiderweb of like 10 hoses. I actually want to try buying a set of '01 - '02 GS500 carb top caps and see if they fit the '04+ carbs. They use the same diaphragm part # and the carbs look similar so they might fit.

Good point BS. I don't have any direct experience with the later model carbs. A bunch of vacuum lines and T junctions gives a bunch of places for a vacuum leak to exist or a hose to come off or go bad. Plus it's a lot of opportunities to hook it up the wrong way.

But it's not really that complicated. If you methodically follow the vacuum diagram and replace the Ts and hoses with new ones you cut as you go then it should be simple enough. Very simple compared with sorting out jetting and needle profiles and all that.

I mean, one man's complicated is another man's simple I guess? My dad continues to think anything electrical is "complicated" and he even tried to figure out if there was a way to put a carburetor on his TU250X. To me, electrical and digital is super easy and I'd 1000x rather be tuning with my tablet and an OBD2 adapter than with jets and washers and needles and guesswork.

You guys are great! Thanks for all the helpful advice. I have the carbs off again and my float height tool came in yesterday so i measured the height on the right carb that the cylinder was not firing and... yep, way off! I bet that's what is was. I also checked the left side and it was only off a mm or two. The reason it was way off was when I cleaned it the first time the needle was stuck/gummed in the seat and I pulled up on the float to get it out and I'm sure that's what put it out, a lot. I actually had to use carb cleaner and needle nose pliers to get it out of the seat. That's why I ordered new seats/valves. I also had a good look at the vacuum lines and they appear to be ok. I'm just charging the battery now and will put the carbs back in tomorrow after work and report back on my progress. Thanks.

I recommend you do what I almost always fail to do. While the carbs are off, replace all of the o rings and do a thorough cleaning.

If anything was "gummed up", then I guarantee the pilot jets are clogged. And the rubber parts that come in contact with fuel are probably shot, and all other o rings are probably hard and flat.

Hear me now and believe later. Right now is the best time to fully sort these carbs and it's false economy to shortcut and skip steps. I learned this over and over, the hard way.

Quote from: Trolleywire on October 26, 2021, 07:31:09 PM
The reason it was way off was when I cleaned it the first time the needle was stuck/gummed in the seat and I pulled up on the float to get it out and I'm sure that's what put it out, a lot.

Woah...yeah thats a sure way to screw things up by A LOT. That is absolutely not how you are supposed to remove the float needle and seat....you are supposed to remove the float first, not bend it out of the way. The float is a piece where a tiny little adjustment will drastically change how the bike behaves. Don't just yank on it.

I will also recommend that you use the clear tube method to verify the fuel height when you are done. The float height is just to get in the right ballpark. Especially if the floats have been adjusted before so they are not 100% straight the measured float height might be outside the recommended range in order to get the correct fuel height. In the end fuel height is the only thing that matters. Float height is just a proxy measurement.