Newbie, got a GS550L, having idle issues

[agreendaya]

I just got this bike, had a '78 Yamaha XS400 which was a little too wimpy, sold that to a guy & picked up this awesome GS. The guy I bought it from recently changed the oil, rebuilt the carbs within the last thousand miles or so, etc. It rides great as long as you don't have to stop, then it tends to want to die at idle. I adjusted the idle up so that wouldn't happen using the throttle stop screw, and it will then idle around 1100 rpm for 5-10 seconds then rev up to around 3k. I noticed if I lean the bike to the right, the idle comes back down to where it should be, does this mean I've got a petcock issue?
I've tried warming it all the way up then setting the idle to around 1100-1250 or so, but if I go off and ride it it dies after stops, I have to use the throttle to keep it from dying, if I do this for a bit it'll then idle right happily away.
The bike is being hard to start when cold, I can hit the electric start all I want,
kick it a bunch, and finally after a while it will just start perfectly with no rhyme or reason. When it's warm if fires right up with one kick or hit of the button.
Sorry for the long post, and thanks in advance for the help!
P.S. I tried the search, and wasn't able to find anybody with similar symptoms, apologies if this has been covered before.

 

[Steve]

First of all,

Second, even though the previous owner said the carbs were "rebuilt", you probably have no idea what he considered a "rebuild". You will be far better off to do them yourself, with the proper stuff. Do NOT waste money on "rebuild kits", they often have less-than-standard parts and not nearly enough of them. The brass pieces you have are likely in very good shape (maybe a bit dirty) and all you need to change would be the o-rings. GSR member Robert Barr has a site where you can order complete o-ring kits rather inexpensively. Go to cycleorings.com and look up information for your bike.

Your erratic idle issue sounds like bad o-rings in the intake tubes between the carbs and the engine. You can get those from cycleorings, too.

Hard starting when cold can be a combination of two or more things. You are already having problems with your carbs. However, even with perfectly-tuned carbs, if your valves are too tight, you will have a hard time starting the bike.

BassCliff has a wonderful site where he has gathered a lot of the wisdom found on this board. He will be along shortly to give you his little "howdy-do", so get prepared to be overwhelmed with a TON of information.

.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. agreendaya,

Thanks for the intro Steve.

Yes, I have gathered much information from the gurus here on this site. There are several TLC tasks you must perform to get your bike in tip-top shape. Replacing intake boots and O-rings, properly cleaning the carbs, checking the charging system, etc, are just a few of the many fun activities you have to look forward to. It may sound a little daunting at first, but if you do it right the first time you won't have to do it again for another 25 years or so. OK, I'll shut up now and just say "Howdy!".....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

 

[mike_of_bbg]

Welcome. I think Steve and BassCliff covered the basics. Thanks for including your location in your profile. I'd also recommend that you include your bike info in your signature. You didn't mention what year your bike was. The GS550L was made from 79-85, and there were 3 different carbs setups during that stretch. You said "kick it", so it's most likely to be a 79 (the only year GS550L intersected with kick starting), unless you were actually kicking your bike and not kick starting it

 

[agreendaya]

Thanks much for the welcome, that looks like a huge wealth of information, this could take a while to get through!
Whoops, my bad, it is a '79. As far as rebuild, it looks like most gaskets in various places on the bike are new or in good shape. Seems like o-rings would make sense, I'll get some of those ordered up, and will shoot for a valve job this weekend (gotta give it enough time to totally cool off, and I've still got to ride the thing to class). I just pulled the plugs, and 3 of the 4 are very carbon fouled, the other looks pretty good, just a little black & mostly tan. I would've thought that I'd be getting the opposite if the o-rings are leaking extra air in...

And here's some photos. Looking under the tank it seems like it was originally red, then repainted this blue...

Rode out to San Luis Bay/Avila Beach the other day with the girlfriend.

Apologies for quality on this one, el cheapo camera+my "garage"=ugly pictures.