'81 650 Maxim - Likes to die in intersections...

After searching these forums for a while, and realizing that I know very little about my motorcycle, I'm taking the plunge and putting up a post. Thanks in advance if you can help!

As of today, my bike has decided to sputter and die in every major intersection that I come to. Which has resulted in a number of chaotic situations of me having to push my bike through a lot of traffic.
I hadn't rode my bike (1981 XJ650 maxim) for the past 10 days because I had been away. Before I left it seemed to be functioning fine.

So a brief summary of the problem:
The bike starts okay at first, I can ride it for a while normally. After a bit of riding i'll have to bring the bike to a stop at a traffic light, where it idles fine, but when I apply the throttle to take off the bike loses all power, sputters for a while, and then stalls. Sometimes it will catch before it stalls and take off like a rocket, but usually it just stalls. Every time this has happened i've been able to get it started again after 5-10 minutes of trying, but then it will stall again at the next stop.

What I have done to try and fix the problem:
-Filled up with gas
-Boosted my battery (it had died during one of the sessions of trying to restart the bike)
-Drained a bit of oil because it was at the maximum marker
-Checked the spark plugs for spark (they all had a good amount of spark, but were sooty)

The carbs were cleaned at the beginning of summer, and again about a month ago.

Any ideas of what the problem could be? I'd appreciate any insights, but remember that i'm fairly new to biking, and even newer to bike mechanics. That said, layman's terms would be appreciated!

Thanks a lot!

 

How well was the carbs cleaned? Did you sync the carbs after cleaning them? Have you check your valve clearances?

 

I'd run a bottle of Seafoam thru it and see if it cleans up any jets. Then start looking at the sparks right after it dies on you. See if they're wet. If so I'd look into the petcock

 

Get a New Set of Plugs in it.
Lets have a look at the Old Plugs.

Pull the Old Plugs ... Line 'em up: 1, 2, 3, & 4 ... close together.
Take a nice, well lighted, close-up picture of the Sparking ends and put them in a Post.

Look at your Carbs and locate these "Screws" on ALL the Carbs.
These are the Pilot Mixture Screws.
Determine if they are Visible or Hidden by a Plug.

We'll proceed in getting you running a bit better after we see the Plugs and find out if you have access to those Screws or if the Carbs will have to be removed to begin a Cleaning and tuning process.

 

Since you said the plugs were sooty it sounds like you could be running rich - Rick is right need to see the plugs and go from there....

 

Gentlemen,

Thanks for the input. Here's a picture of my spark plugs. I'm not sure if you'll be able to tell, but the plugs are black/sooty/dry. Also I do have access to the mixture screws.

Also, I did check my valve clearances last time I clean my carbs.

A side note: Do you think that overheating would have anything to do with it, seeing as the problem doesn't arise until i've been riding for a while? I'm running 10w-40.

Thanks again for the help!

 

Results:

3 Cylnders Running too RICH >> Bogging you out.
1 Looks Lean >> We'll adjust it for Peace of Mind.

Locate Pilot Mixture Screws:
Tweak >> NOT "Turns" Fractions of Turns.
As you further Fine Tune:
Degrees ... Barely moving the Screw at all.

Begin with:

1) Showing slightly RICH. 1/8th of a Turn IN (Down)

2 & 3) Showing Too RICH. 1/4 of a Turn IN (Down)

4) Showing slightly Lean. 1/8th of a Turn OUT (Up)***

The 4 Plug is also showing a Clean Ground Electrode Arm.
If the adjustment of the Pilot Screw doesn't improve the way 4 looks, ... investigate that Hole for an Air Leak.

Throw-in a set of New Plugs.
Have those there "Media Blasted" clean and we'll use them for a Plug Chop after the initial correction.

*** > I can't tell from the Pic ... But, if the Ceramic on the 4 Plug is eroded or has fractures. Double the Tweak and make that Hole run Richer!!!

 

Some good advice has been given so far. If you get your carbs adjusted and still have the problem, make sure all the spark plug caps are on tight and that the resistance is good. I had a bad plug cap and that made for some initial hesitation from a standing stop, especially after it was warmed up. I found this out when I first started the bike and carefully put my hand on each header pipe to make sure all cylinders were firing. Number one was not, so further testing with an Ohm-meter confirmed the problem.

Hope you get things solved soon,

 

A stupid question of sorts, but one that relates to the topic at hand. How often should you clean out and/or resync your carbs.

Thanks much and sorry about the topic hijack.

 

as long as you do the regular winterizing of your bike and keep the gas from gumming up and varnishing your carbs, you shouldnt have to clean them much at all. syncing shouldnt be required unless you do a full teardown on the carbs.

I am a firm believer in seafoam to keep things cleaned up on the insides.
I haven't tried it yet, but they say it works to stabilize the gas during the winter. I do use it to keep things clean in the very very tiny passages.
your mileage may vary

 

If you haven't been through the Rack to "Dust and Clean" them ... you should.

You can accurately measure the depths of your Pilot Mixture Screws to return them to the precise settings before removing them.

The Diaphragm Piston Rubbers should be inspected.
The Diaphragm Piston Bores ... Scrubbed and Polished for performance.