my 1981 missing on 2

i am new here
i have a 1981 xj650 somebody layed it down 14 years ago and it sat till i bought it
i have cleaned the carbs i have cleaned everything in them and i do mean everything
now it starts and runs with choke on
exhaust pipe on number 2 is cold when others are hot
i can pull the plug out on the wire and i see sparks
adjusting the fuel mixture screw doesnt seem to help
any suggestions would be great

 

possible problems:

-a stuck float valve that doesn't let any fuel into the bowl....
-a dirty beanie screen on the float valve
-float level way off or float installed upside down
-clogged siphon tube for the enrichment circuit
-clogged passage in the bowl that the siphon tube sits in
-clogged idle jet or passage (the holes in those buggers are TINY)

since neither the idle nor the enrichment circuit is getting any fuel to that cylinder, I'd start with the float valve and go from there. Check the fuel level in that bowl before you take it off again. It should be within 2mm or so from the line where the bowl and the carb body meet.

soon someone will chime in with more possibilities, but that's a start

 

thanks stereomind the floats were way off now its running pretty smooth

i can fix just about anything once i know the problem my only issue is trouble shooting

 

i got it running real well
but it was flowing gas aout of 4 so i pulled the carbs and adjusted the float in four
waited a day to start it
it fired right up no choke but new problem started running at 3000rpm and 2 and 3 arnt running now
somebody help please

 

it has gas in the bowl
and i pulled a plug and grounded it against motor it gets spark

 

Swap the Leads to from the Coils to the wiring harness and see if the problem shifts to 1 and 4.

If it does you have an Ignition issue that might be related to the Coils.
If not ... you have a problem inn Fuel Delivery that would be related to the Pilot Mixtures.

It's not at all uncommon to have a Pilot Mixture problem on a bike that sat for a time.
You have to be sure the Pilot Fuel Jet is unclogged.
You have to remove the Pilot Mixture Screw from up-top and flush the Air Passage down through the removed Pilot Jet.

That ought to allow you to adjust the Mixtures with better results.

 

i know its not a dirty carb problem because i cleaned them out following a forum post from rickcomatic they are spottless inside the only thing i need to do in them is polish the diaphram barrels

it was literally running perfect 2 days ago

however the coil issue sounds like it
if iswitch the wirs does it matter witch ones go where am gonna lock it up if i do it wrong

the only thing i did between now and then was adjust number 4 carb float and i lubricated the throttle cable and the throttle assembly on the outside of the carbs with some wd-40
when i started it today it idled rough and i turned the throttle it went up to 4000then very slowly went down to 300 and wont go below

 

You can swap the Coil Wiring without any problem. The Ignition is a "Wasted Spark System" Both the Coils are firing all the time ... but, only one fires the Plugs on the Ignition Stroke.

There's nothing to worry about.
It's the prescribed Test for a possible Coil Defect.

Which brings us to the issue of AGE of Components.

If you find that the Coil is at fault. Instead of buying one Coil to replace the defective one ... you might want to consider buying a set of NEW Coils and benefiting from the Power and reliability of some State of the Art Coils from DYNA or Harley.

Those who have replaced their Factory Coils with modern ones have all commented on how well they perform and allow for using High Performance Plug Wires and Caps.

 

RickCoMatic,

Will the defective coils cause only one cylinder to miss? I bought a 83 XJ750 for my neighbor. It was only running on cylinders 2,3,4 at first. Tonight I found a loose end on the #1 plug wire and put it back on and cleaned the plug. I restarted the engine and #1 fired just briefly. I restarted the engine and #2 and 3 only was firing. The pipes for #1 and 4 were cold. I restarted it a couple more times and it was back to #2,3 and 4 firing and the pipe for #1 was cold . I looked at the fuse box under the seat and found a fuse with foil around it and all the other fuses were gone and two wires tied and twisted together to replace two fuses.
This is a very decent looking bike and I only gave $525 for it. Oh, the tach is crazy also. It goes to zero when you shut the engine off. When started it goes to around 1000 and stays there. If you rev it up several times it creeps up to around 3000 and stays there until the engine is cut off again. I don't know if I need another tach or not. I saw another instrument cluster on ebay that looks identical to mine but off of a XJ650. I don't know if they are interchangeable or not.
I first thought that the problem was with the carbs dirty, but since the firing is jumping around to different cylinders I am not so sure now. Any help you can give is most appreciated.

PS, I just checked again, cylinders 1 and 4 are dead again. Tomorrow I will try and switch the coils around as you described earlier to see if that makes a difference. I did notice that in the process of checking the plugs when I first started fooling with the bike that when I would turn the ignition or cut-off switch off that it would backfire even though the engine was not running :?: . It acts more like an ignition problem than a carb problem.

Ed

 

Ed:

It's extremely hard to kill and XJ-Bike. You have to be deliberately nasty to the thing and it will still come back strong.

Everybody who a an Early '80's XJ-Bike needs to get on the same page with regard to some Preventative Maintenance and Repairs.

1. After nearly a Quarter of a Century there are components that have outlived their design parameters.

Fuse Panels and Clips being the Number-1 item to be replaced on the beloved Yamaha Shafties.
The Fuse Panels were cheap when the built the Bike.
Age had deteriorated them to near self destruct a few years ago.

Replace the Fuse Panel with a Modern Fuse Panel and you'll eliminate a good deal of your Electrical Problems in one fell swoop.

Coils and Petcocks:

The Coils are Old and prone to failure.
Those of us who remember having a Hot-Rod Car as a kid knew one of the first things we'd have to do for the enjoyment of being able to get the thing moving away from a Red Light was to have a High-Performance Coil.

There isn't anyone I know that will tell you to try and resurrect the Stock Coils if they have deteriorated from sitting around and are cracked or susceptible to breaking-down and losing spark.

Petcocks will develop a leak.
You can buy a kit and struggle with it ... or,
Buy another new Petcock that will last as long as the old one.

My advice to you is to eliminate ALL your Gremlins.

Replace the Fuse Panel:
(Wirewerks.com or our resident Merchant)

See what happens after you have a good electrical path working for you. You might find-out that you don't need Coils after all!

As for RPM Creep and Tuning Issues:
Clean the Carbs
Bench sync them
Install them after cleaning with an inline fuel filter.
Do the tuning and enjoy riding a bike that was engineered for leting people have fun!