misfire!!!!!

Yeah I finally got my bike up and running.(1981 Yamaha 650 maxim) ok here is the list. New spark plugs, battery, in line fuel filter, carb kits, really clean carbs. The problem I am having is that sometimes when I am riding I am having a powerdrop like I just lost a cylinder. But when I keep riding it seems to fix it self and will run perfect. And then later it will have a powerloss. I am pretty sure that it is the number 3 cylinder I have great spark from all of the spark plugs. during these episodes. It will spit and sputter you here it trying to catch itself. My friend has a cb900 and was having the same problem. He said he just drove it a couple of weeks and it cleared it self up. He says no matter how well you clean your carbs there is always some gunk that comes from somewhere. But there more you ride it will clean it self out? Any suggestions?
Joshua

 

floats that are set too low could cause something like this... or a loose piece of dirt in one of the float bowls.

what makes you think it's the #3 cylinder?

also.. what part of Oklahoma are you in? Seems like there's not many XJ's around these parts...

 

From Purcell about 20 miles south of norman. The number 3 because of the way it sounds when it is running.

 

bang bang donk bang.

 

Any ideas?

 

please somebody help
pretty please???

 

Joshua,
I would assume you have spark until proven otherwise.
First culprit I would look at is your spark plugs. What are they telling you? Chop the throttle and kill switch the next time it happens and pull over. Yank your plugs and have a look. Wet, dry? If they are wet, your spark is gone. Dry, well, let's look at the carbs. Have you cleaned them recently? Could be you have a sticking float/seat. Works fine 'till the fuel runs out. Another suggestion is to run some SeaFoam through the fuel tank. If you have any goo in there, it'll clean it out somewhat. Let us know what you find.

 

Pull the Ignition Side Crank Cover off and see if there's moisture in there. Leave the Cover off for some testing.
Clean the Ignition Pick-up's with Alcohol and Q-Tips.
Clean the Igniter Box Plug-in's thoroughly and re-connect the Plug-in's
Do the same for the Coil's Plug-in's to the Wiring Harness.

Install a new Fuse Panel if you haven't already.

Don't assume its #-3 !!!

Look at all four Plug Caps ... check for a hairline crack.

Begin troubleshooting Ignition.
Resistances.
Plug Wires for cracks or chafing.
Test Coils.

You can swap the Coils Wiring Harness Plug-in's and see if the miss goes to another hole. If it does ... you have a Coil Problem.

You might have the onset of a Charging Problem and the miss is from Current falling below the operating threshold.
For kicks:
Check the length of the Alternator Brushes.

 

Ok I was able to pull over safely and and check the plugs when it was acting up. All of the plugs were in good condition. Then i went to check for spark. Cylinder#3 wasnt getting any spark. The spark plugs wasnt wet or fouled it wasnt putting out any spark. I didnt notice any cracks in the cap but I will pick one up tomarrow since they are inexpensive. Anyways any advice?

 

Those Coils have gray beards.
It wouldn't be such a bad idea to splurge for a pair of new Dyna Coils.

Some of their Coils are straight bolt-on and go.
They have others that require a little fabrication to get them on.

There are others I am aware of who have swapped original coils for Harley-Davidson's.

I wouldn't be going too far out on the limb to recommend you find yourself a brand new set of Coils and get your ignition system a quality upgrade.