Difficult Warm-Up: Idle, Throttle

[Euphonious Jack]

Year: 1981
Model: GS650L

Problem: This bike takes an embarrassingly long time to warm up. It turns over fine. With full choke, it starts fine. But then it's a 10-minute game of mess-with-the-choke. With full choke, the RPM's hang around 4000, when I push the choke down; sometimes it dies, sometimes it hovers below 1000, sometimes I give it gas and it dies.

When the bike finally maintains a constant, comfortable idle, the throttle issue persists unless really, really warmed up. When I give it gas from low gear, it puts or dies. Not a good feeling when pulling out of a stop into an intersection.

What I'm asking is, what will it take to start and ride this bike in a normal, safe way?


Variables:

*The carbs were recently pulled, ultrasonic cleaned, and o-rings were replaced.
*Because the bike is such a bastard to keep running, the fuel mixture has been set slightly richer and the idle is set around 1400.
*The weather is nice, 60's at night, 80's at day.
*The diaphragm of the petcock was removed - leaking fuel.
*New air filter, fuel, oil filter, oil, and plugs.

Thanks in advance for recommendations in this matter.

 

[Danjal]

Youre too rich IMO. If you give it throttle and it does thats one indication of it. You could also have an airleak on the intake boots if you have those. The boots or metal around them could swell up from heat and seal up.

When was the last time you cleaned your carbs?

 

[Steve]

What is your definition of "deep cleaning" the carbs? Just spraying heavily with carb cleaner isn't enough.

Which "seals" were replaced in the carbs? There are a BUNCH of o-rings, I guess you could call them "seals".

I will have to respectfully disagree with Danjal, and suggest that it's running LEAN, not rich. When you "cleaned" your carbs, did you also remove the idle mixture adjustment screw? There is an o-ring around its base and a very tiny passage for the idle mixture to go through. That is a very common place for crud to build up and keep the bike from running.

Also, when you put the idle mixture screws back in (assuming that you removed them for cleaning), where did you set them? A good starting point is three full turns out from lightly seated. At that setting, you should not need any more than half "choke" to get the bike running, and will be able to turn the "choke" off well within a minute, while you are riding off.

What new fuel filter did you install? The only filters that are stock are the one around the petcock intake on the inside of the tank and the screen on the intake of each float valve in the carbs. There should not be any other filters in the system. Too many of them are too restrictive for motorcycle use. If you absolutely insist on having another filter, make sure it's rated for a gravity-fed fuel system. A good place to look is the lawn tractor aisle at Lowe's.

Why did you remove the diaphragm in the petcock? That is your first line of defense against having your carbs overflow gas into the crankcase. If, for some reason it was not working correctly, FIX IT, don't Band-Aid it. By the way, the success ratio for petcock rebuild kits is about 10%, so you will be better off just spending a little more money ONE TIME and getting a new petcock.

The only practical way to clean the carbs is a full dismantling to remove all the non-metallic pieces, then dipping the carbs for up to 24 hours in Berryman's Carb Cleaner Dip. Follow that with a warm water rinse, then carefull assembly with a new set of o-rings from cycleorings.com. Set the float height to the proper 22.4mm, make sure your jets are correct for your engine (if you have stock airbox and exhaust, stock jets are fine). Do a "bench sync" to make sure all the carbs are opening about the same amount at about the same time, put them on the bike. Start the bike, warm it up. Install a set of vacuum gauges to do a dynamic sync.

Also, since you might have other questions about the bike, it would also make sense to check the valve adjustment to make sure that they are right, too. Valve adjustment should be performed before a carb sync.

.

 

[Dave8338]

Valves adjusted?
Intake oring replaced?
Why the additional fuel filter?
Air filter over oiled?
Battery holding a full charge?

Replace petcock...



Welcome to the GSR.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. Euphonious Jack,

Long warm-up times are indicative of tight valves. Your bike would benefit from a full dose of TLC; valves, carbs, electrical, etc. In your "mega-welcome" you will find a couple of maintenance lists that will lead you down the path of GS nirvana, if you take no shortcuts. If you stray from the path you will be cursed with stuttering performance, hard starts, dead batteries, and become stranded on the side of the path instead of riding briskly down the path. Do it right the first time. Let's get started...

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

 

[Danjal]

EJ didnt you have a line in your post before stating that it blew black smoke at an idle while warming up or am I imagining things here?