Running slow, stalling out, high idle..carbs?

[somaticshorty]

Hope this is the right thread. I am new and learning, learning, learning. Forgive my lack of terminology and possible lengthy explanation as a result.

81 GS400L

Riding yesterday, started fine and seemed warmed up. Taking off in 1st gear, it would idle high but barely move. Gears changed fine, but sluggish. Id have to really put on the throttle to get any movement. Shifted fine. But Id have lots of throttle on, so high RPM but only going btw 40/50km, when I would shift to 3rd then it just sounded like it wanted to stall out and the bike would not pick up speed.

It was feeling a little better have about 20 minutes, then I hit the 80Km road, got the bike geared up and moving upward 80km but it felt like a huge struggle and then it died on me.

Pulled over, wouldn't start (power but wouldn't turn over), very hot against my right shin, little smell but not of exhaust or gasoline, sat for about 20 minutes and then it started again.

On the way home, it was worse, could barely get going to 50, or up an incline. Would have to keep throttle on when stopped at lights or else it would stall.

So reading through this forum..Do I start with cleaning the carbs? or does it sound like a different issue?

Your input much appreciated!!!!

further background if this helps:

Bike is new for me and my first bike. Only put on about 100kms so far. Hour city/side road ride every 1-2 weeks. Starts with choke on, takes a few minutes push in the clutch and its fine.
Lots of gas, oil fine, new battery.

[BassCliff]

Greetings and Salutations!!

Hi Mr. somaticshorty,

It sounds like you have a 30 year old motorcycle that needs 20 years of maintenance. In addition to all of the regular maintenance found on the lists in your "mega-welcome", it seems your clutch is slipping. Let's roll up our sleeves and get started.

Anyway, let me dump a TON of information on you and share some GS lovin'.

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Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. 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. I will put you on my prayer list.

Thank you for your indulgence,

BassCliff

[somaticshorty]

that would be Ms.SomaticShorty

okay will starting reading on clutch slipping

thanks for the reply and welcome. I am looking forward to learning...and sound like the 20 years of needed maintenance on my bike will offer the opportunity....sheesh.

[mike_of_bbg]

Wait a second.

So, where you said push the clutch in and it's fine after a few minutes I assume you actually meant choke and not clutch? You are turning the choke off, right?

You talk about high RPM. With clutch slip the motor will rev faster (usually drastically) but the bike won't go any faster. That's when the motor is over-powering the clutch. But maybe what you're saying is that you're keeping the gears low to have any power. You talk about it struggling in 3rd gear. Were the RPMs shooting up then? Or was the engine struggling to handle the load? That sounds more like carb issues.

[Big T]

Sounds like it's only running on one cylinder

[BassCliff]

Hi,

that would be Ms.SomaticShorty

Please accept my apologies.

It's a pleasure to make your acquaintance.


Thank you for your indulgence,

BassCliff

[somaticshorty]

Yes, Mike, I did mean to say choke not clutch. I did turn off the choke.
and exactly...i was in 1st and 2nd to get power, but the RPM were very high. Once I shifted into third id lose that power, RPMs were still high, Id shift to 4th, even though speed was not there, to try and drop the RPMs but id lose the power and not be able to get any more speed, then the bike sounded like it was idling down to stall out. So settled at 3rd gear, bike only allowing about a max of 40.

Big T, Are there other signs, of running on one cylinder?

[tom203]

thanks for the reply and welcome. I am looking forward to learning...and sound like the 20 years of needed maintenance on my bike will offer the opportunity....sheesh.

Basscliff meant 20 years of neglected maintenance to catch up on! Cheer up, you might be able to do it by winter depending on where you live.Anyways, start with simple checks like fuel tank petcock- make sure it perforrms as intended and allows decent fuel flow. also make sure that gas cap is not causing a vacuum in tank to develop ,restricting flow at random times.

[mike_of_bbg]

Once you get the bike running you can check for heat from the exhaust headers (carefully, they get VERY hot - lick fingers and tap-touch). If one is cool then that cylinder isn't running. You can also try pulling each of the plug wires one at a time while the bike is running. If pulling one of the caps makes no difference then that cylinder isn't doing anything.

As tom203 mentioned, if your gas cap isn't venting then you'll build up a vacuum in your tank and fuel will refuse to drop into the carbs. That's easy enough to check - if it stalls remove the cap for a second, put the petcock on prime for a few seconds, back to on, and see if it suddenly gets better.

Do you have an extra spark plug? If not think about changing yours and carry one of the old ones as an extra when you ride. If it stalls and won't re-start, remove the wire from each installed plug, and put it on the spare plug. Hold the outside against a metal part of the motor to ground it, and see if there's a nice blue spark when you're trying to crank it.

[Big T]

Big T, Are there other signs, of running on one cylinder?

As mike says, one exhaust pipe will be hot, the other will be colder

Lack of power, inability to climb hills,etc

Did this bike ever run well?

What have you done to it?

[somaticshorty]

Yes, other than idling high sometimes, or stalling on its own when waiting at a stop light sometimes, the bike has been running okay since i bought it a few months ago. It was just my last ride that this problem happened.

As it was running okay, I haven't done anything to the bike since getting it, except replace the battery.

Thanks for all the suggestions, look forward to trying them.

[mike_of_bbg]

Idling high is usually a sign of an intake leak. On the models with intake boot o-rings those are notorious for getting old and cracked.

http://cycleorings.com/intake.html

You'll notice the boots themselves are two-part pieces with metal on the head side and rubber surrounding it and continuing to the carbs. If the rubber starts to deteriorate with age it can develop cracks and perhaps separate from the metal part as well, leading to air leaks.

The extra air causes the high idle. It also causes your bike to run very lean and thus, poorly.

[Big T]

Shorty,

I've got a few questions

1. Is your bike a 450/4 valve model or a 400/8valve model?
2. Where in the world are you?
3. Your problem could have a lot of a causes
a. Rust in gas tank now stuck in carbs
b. Bad ignitor
c. Carbs boots ( as above)
d. Bad petcock
e Other

[somaticshorty]

Big T, I know the bike is a 400, I do not know of the number of valves...??

Im located in vancouver Canada

Hoping to start tackling this issue in the next while, I will update on the findings