I just finished rebuilding my 2005 GS500F engine's top end. Finally, I got to test the bike running without burning a quart of oil per minute. Now, before reading on, understand this is the first carburetor I've ever touched and have only cleaned it once, all while learning as I went (I cleaned it before the first fire up after buying it. I bought it knowing it didn't start). Although I know I'm pretty good with mechanical issues, a carb is something that I have yet to completely understand enough to be able to diagnose.
Initially starting up, I used the choke, which would start it okay but made the RPM's jump up high very quickly. When trying to moderate the RPM's by lowering the choke, it would try to die until the bike was warmed up. While this isn't my main concern, I believe it's one of the symptoms.
Once warm, I can get the idle to stay within range. However, when you throttle/rev the engine, it has a 99% chance of sticking... or staying at anywhere between 3K and 5K RPM. It won't go back down, and I have to shut off the motor with a higher RPM. I found a post with a somewhat similar issue, and he mentioned the fix being a washer's placement on a "user-adjustable" part, and I think he was referring to the pilot screw. It's the only part on the diagram I can find with a washer and spring as he described. He said that he placed the washer on the wrong side of the spring, which hindered the spring. Know that I haven't adjusted this pilot screw, so if there is a problem with this, it was pre-existing. Perhaps it needs adjusting?
Also, I initially started the bike on prime, and then again on reserve (I'm keeping the gas low until I get it going correctly). There was no difference in the two. I admittedly was hoping that the gravity fed gas had something to do with the "sticking" symptom.
I thank you ahead of time for any help or ideas. I can't wait to finish the mechanical part of this bike and start on the final paint job.
Sounds like an air leak around the carb boots.
Can you provide a link to the thread with the screw/washer discussion?
i have the same year and mine is a little similar. have you turned down your idle adjusting screw/knob, its a white knob on the bottom in between the carbs ? Its a tight fit while the bike is running so were a small glove to prevent burns
I tried to find the article again but no luck. I will try again later. However, I did find this one that should help me: http://gstwins.com/gsboard/index.php?topic=41199.0.
So how do you check for air leaks on the boots? And by boots, you mean the round rubber pieces that connect the carbs to the intake right? I've seen people say something about WD40 to check for it, but I'm not sure how you would do that. I guess it would bubble? Or would it be sucking air in through the leaks?
And as for the idle adjustment, I just didn't think it was that since it idled fine until given a twist of the throttle. It's definitely worth a try though.
Yeah when I first played with the knob it did the exact same thing. It would idle fine but when I gave it a twist on the throttle it would stick my rpms in the same range as yours does. It's real easy to play with and if it is the problem you'll find out real fast
The idle rpms will increase when you spray wd-40 (or better starting fluid) at varoius areas along the air/fuel path. e.g the carb boots, carb diaphrams, etc.
Thanks guys. I haven't had a chance to try anything yet, but hopefully tomorrow I can toy with it for a bit. I'll update this post as soon as I know something else.
i think what x-ray was trying to say...if you spray starting fluid around the carb boots and it does raise the rpms then u have a leak...but if not then it would be a different problem but according to many other post...a hanging idle problem would be an air leak somewhere around the intake boots!
From the air box with the filter, all the way to the boots bolted to the head. If there is an air leak it will cause hanging RPMs. CV carbs are very touchy about the air intake.
Could that also be the case if I rev it up an it takes longer than it should to rev back down?
Problem seems to be solved. :woohoo:
Even though I highly doubted the simplicity of an incorrectly adjusted idle being the problem, it seems to be the culprit. I toyed with the idle today and found out that it's very sensitive. I had the engine warmed up completely and the idle was at 1250, which I thought was in range. After getting it to repeat the hanging idle issue, I lowered the idle to 1000, but it seemed like it wanted to die, so I brought it just a tad up to about 1100. I then "commenced" some more testing, including a road test, and it drops idle back down like a champ. I'm waiting for the problem to arise again, because I'm so surprised that it was that sensitive.
I still plan on testing some starting fluid on it with everything sealed up. I'll follow the directions you all gave me, because I want this to be in top condition when I put it up for sale (not that it's still having problems, but just to double check). I'll have to put up photos of the final bike to show off and thank everyone for their help with everything.
I have suffered with this same issue with a 2004. No matter what or how I approached the situation I could not get the bike to idle right. It was either too high or too low. No matter what I did. After checking for air leaks and found none; I looked at the valve shims.
The two exhaust shims were very tight, from my limited understanding and assembly of many different postings from this web site I determined that the culprit had to bee the tight shims.
So I tried to fix it and I did such a bad job that the bike is being triaged by the local shop. Your post says that you built your engine, nice job; did you have to replace any shims and are your exhaust valves with in spec; some like the clearance to be between .08 and .13 mm.
No I am assuming that during your rebuild you did replace the shims?
I had an SV 650; I owned for three years, never had any carburetion issues period. The 2004 GS is more than making up for the lack of issues with the SV.
You would think with such a simple and efficient engine design; these bikes would not plague their owners with continued tinkering with the dam carbs.
Could be my expectations are truly misaligned; but this Suzuki platform should be a very simple, change the oil and tires then point and shoot. Maybe I just don't get it yet.
Let us know what happens over the next few weeks. Good luck