two cylinders not firing.

So, I started this project back in 2010, and with the help of this forum rewired and chopped and rebuilt the carbs (for the open headers and pods) getting it almost complete. Then life happened and it went on the back burner for almost a decade....



Im back. I have somehow rekindled the fire and I want to finally ride this thing...

So, after a little tinkering, I hooked up a battery and tried to fire it. It struggled to life for the first time since I tore it apart and I was ecstatic. I reved it a few times just to listen to the howl and shut it off. It wouldnt idle, which was no surprise, the valves havent been adjusted and the carbs havnt been synced. But then I noticed that only cylinder 3 and 4 were hot.

I took off the carbs and checked to see if maybe they had become plugged up again. Nope.

Then I fired a little starting fluid in the carbless boots. Sure enough, only 3 and 4 would fire.

I switched 1 and 4 leads and still, only 4 would fire.

I went and got a compression test kit, 1 - 120 psi 2 - 120 psi 3 - 125 psi 4 - psi

I figured the valves would need to be looked at, but I figured it should at least fire.

I took both 1 and 4 leads with plugs in and grounded them next to each other and they both seem to spark at the same time.

Please Help.

PICS - https://photos.app.goo.gl/rw6txf6RJJ8qU5AL8

 

if 3 and 4 are firing that would say that coils are good as one coil fires 1 and 4 and the second coil fires 2 and 3 . make sure that's how you have them hooked up
try swapping the spark plugs see if that changes which cylinders fire up
sounds like a fuel issue . check setting on mixture screws for 1 and 2 ,open them up a little more.

are plugs wet in cylinders that do not fire?

carbs bench synced?
carb bowls wells for enrichment circuit clean ? spray jets through them. sand down the red tube on can of cleaner so it fits in the hole at bottom of bowl.
could be you just need to clean passages in carbs

fuel level s wet set?

 

I havent checked the plugs to see if they are wet, Ive been shooting a small bit of starting fluid in the intake with the carbs off. If i spray 1 and 2, nothing... If i spray 3 and 4 it will fire right away. I figured I wouldnt try to play with the carbs until I can get it to fire on all four.

 

starting fluid will foul a plug quickly if not firing well.

try swapping the plugs from 3 and 4 into 1 and 2 and check the plug gap on plugs that do not fire

if you swap plug wires on 2 and 3 does that change which cylinder fires?

 

Not a good idea to spray into cylinders without carbs installed. I would recommend reinstall carbs , put 4 new plugs in and then see if it runs .

 

I picked up an 83 xj1100 last fall. Had a safety inspection done on it and it has been a great bike. Took it out today and it started getting boggy. Stopped for fuel, and noticed two and three were cold. I disconnected one and four and tried to start it. Nothing. So I'm looking forward to changing the plugs tomorrow. I just wanted to say thanks as this site has been a goto since I bought the bike.

 

Cylinder 2 and 3 share an ignition coil. May want to check for spark on both wires from that coil

 

Do I need to take the tank off or is it just under the seat? It's not the plugs. So just trace the wires back?

 

you will also want to check ohms on pickup coils a failed pickup would make no spark on 2 and 3

 

Yes, they are under the fuel tank. Once the seat is off the fuel tank comes off with a single bolt or clip and removal of fuel and vacuum lines

 

you can do it from the tci the 2 plugs connect to pickups and coils. if ignition primarys fail at tci then check at connector of the ignition coil.

the pickups aer tested from the tci connector any ways