Very rough XJ550 after carb rebuild

Here is a video of the first time running my XJ550 after rebuilding the carbs. They have all been wet set with 3 at 2.7mm, and the 4th at 3.1mm.

I replaced everything in the carbs excluding the main needle connected to the diaphragm. They’re all extremely clean on the inside, and I have only bench synced these carbs, but something else seems wrong.

The bike actually ran pretty well before rebuilding the carbs, I mostly did it for the experience and I haven’t changed anything to do with the engine except the carbs.

Completely releasing the throttle causes the engine to stall, but anything passed slight throttle seems to have no effect. It simply runs this way with no change in RPM regardless of throttle position passed a quarter turn or so.

I’ll be taking the carbs off later today to recheck the wet set, but I’m pretty confident it’s accurate. I have a friend with a set of vacuum gauges to sync the carbs, but, it doesn’t seem like that should cause it to run *this* rough.

Idle mixture needles are all at 2.5 turns out on all 4 carbs.

Anyone have any idea where to go from here?

Thanks.

 

Need to get an IR hear temp gun. I would guess you are not running on all 4. It could be the carbs could be the plugs could be other things. Just start slow and go from there. Pull all the plugs out, insert them into the boots and put them on the head so that when you try to start the bike, you can check spark. If you have spark move on. If not, check the wires the plug boots screw into, make sure the wires are clean and making good contact with the boot prong.

While you have it running, carefully check to see if all four pipes are warming up the same? If not and you know you have spark to all 4, then it is a fuel or compression issue.

You did clean this jet in each bowl. Not the same are ours but you will see it is similar. Needs to be very clean and able to pass air and fuel to make the choke ckt work.
carbs_floatbowl_choke by Tim Brown, on Flickr

 

You’re right. They all get warm but some get significantly warmer. I’ll pull the carbs, got to be that. Rand great before after replacing all 4 plugs.

 

You gave us ne info, did you clean the carbs and put new plugs in at the same time? I would clean up the old plugs and then try it to see if the new plugs are the issue. Do the easy troubleshooting before the hard work on the carbs. If you didn't do the choke ckt jet in the bottom of the bowls you will have to pull the carbs again anyway. Step-by-step troubleshooting now lot of thing at the same time.