GS400 Choke/Idle problem

[DamageCase]

Hello, this is my first post here!

I've got a 1977 GS400 with the stock Mikuni carbs and aftermarket exhausts, with individual K & N air filters. I've been having a problem wherein when I start the bike with the choke on, it revs up to around 4K and stays there. I have to let it do this for about a minute before it will run with the choke off. Occasionally, it will stop doing this for a brief time, but it always seems to come back. Is it possible that I have an air leak somewhere which is exposed when the choke is active, or is it a case of the choke being adjusted improperly?

[BassCliff]

Greetings and Salutations!!

Hi Mr. DamageCase,

After your bike is started, try pushing the choke in so that you keep the revs about 2500 as the bike warms up. 4000rpm is too high to warm up. Are your carbs thoroughly clean? Have you replaced intake boots and O-rings and done all the other maintenance on the air intake system? It's all in your "mega-welcome". Let me share some GS lovin'.


I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

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

[tom203]

Is this bike an old friend or new to you? As Basscliff said, when it starts push choke in -maybe halfway- to keep revs reasonable. My bike takes a good minute to stabilize- I usually just ride off and turn off choke completely in 3 minutes.

[Nessism]

You do realize the bike won't run properly without rejetting since you have changed the intake and exhaust? Common problem and number one reason to leave the bike stock unless you enjoy fiddling with carbs.

[DamageCase]

Thanks for the welcome folks.

I saw the carb rebuild and o-rings material, but the carb stuff looked to only cover the later four-cylinder bikes, and the o-rings were for bikes of at least '78. My boots do not have the the recess for o-rings, and use some kind of flat gasket instead. The bike had the pod filters and the aftermarket exhaust on when I got it. The carbs have been rejetted at a shop, but evidently not very well, because it didn't do this before they messed with it.

Do you think I could, for the time being, just try using a partial choke setting? I will try that next time I can. Really appreciate this forum and its resources, which I have been using for some time now before joining the forum. Thanks!

[tom203]

Thanks for the welcome folks.

I saw the carb rebuild and o-rings material, but the carb stuff looked to only cover the later four-cylinder bikes, and the o-rings were for bikes of at least '78. My boots do not have the the recess for o-rings, and use some kind of flat gasket instead. The bike had the pod filters and the aftermarket exhaust on when I got it. The carbs have been rejetted at a shop, but evidently not very well, because it didn't do this before they messed with it.

Do you think I could, for the time being, just try using a partial choke setting? I will try that next time I can. Really appreciate this forum and its resources, which I have been using for some time now before joining the forum. Thanks!

Sure, you can cope with it any way you want. But remember, the PO and his shop might have done a poor job and you are now the lucky recipient of their efforts! The carb cleaning stuff doesn't care whether you have one carb or a half dozen- the general procedure is the same.