XJ550 carbs yet again...

OK, so I've been fighting with this thing most every night since I got it. I pulled the carbs and cleaned the bottom ends, with the exception of pulling the float valves. Upon winning the re-assembly battle with the airbox boots, I tried to start it. It will still run only for a few seconds before dying, and it has yet to exhibit any real signs of responding to the throttle. So last night, at the advice of Rick, which I unashamedly gleaned from someone else's post, I pulled the carb tops, diaphragms, etc., in order to shoot carb cleaner into the pilot air jets. Now my can of carb spray was waning, so I couldn't give it the giant shot I really wanted to, but I did get a healthy dose down each pilot air jet. After doing this, I reassembled and tried it again. Now, it fires pretty quickly almost every time, but it still dies almost immediately. The #1 header pipe is still cooler than the others, but that's better than before, when 2 pipes would be cooler at pretty much any given time.

I realized after trying it several times that the idle screw was probably set way too high, so I turned it way down. Now it starts without racing up to 3000 RPM, but it still dies after only a second or two. (The vacuum readings improved significantly when I turned down the idle, too, and don't seem to flutter quite as much...duh.) Maybe I turned it down too much (?)

So, here are the questions now: Why might it still be dying after only a second or two? The only thing I really haven't disassembled/cleaned in the carbs is the float valves. Could this possibly be the problem? (I hope not, but I'm afraid it might be.) What is causing it to die immediately when I try to crack the throttle after it fires? And finally, why will it not even attempt to fire or run without the idle enrichment valves (choke) being all the way on? This is really sounding to me like I need to pull the carbs again and get back into the bottom ends, but I'm really dreading the old airbox boot battle...

 

Could your fuel filter be clogged? Maybe its getting fuel, but not fast enough, and starves then dies... I'm very naive at mechanical stuff.

 

What about a fuel starvation issue? Have you determined that the petcock flows enough fuel to the carb bowls? Try running with the petcock in the prime position to see if it gets any better.

My gut feel on your post is that you are running way to rich. The bike starts because you have plenty of fuel on startup. It then races to high rpms because it is getting tons of fuel at idle but it dies when you give it throttle because the mix is too rich. Make sure all your mixture screws are about 2-1/2 turns out from a lightly seated/bottomed out position. If the same occurs try 2 turns, 1-1/2 turns or 3 turns. Really dial it in with a colortune later.

 

I'm using a rigged-up fuel bottle and not the tank. The only "filter" in the system is the screens in the float valves (and that's what I'm afraid of, since I dread fighting the airbox boots again.)

I'll try adjusting the mixture to lean it out. Maybe that'll help.

 

Hey, when you remove the carbs, I emptied out the fuel in them. Now that I am trying to start it back up again, it won't start. Is there some way to jump start it? I have starter fluid... Where would I spray it if I want to help jump start it?

 

You need to PRIme the carbs - meaning fill the float bowls using the PRI setting on your petcock.

 

My feeling is that if it won't start on its own, then you've got something not right. You're not going to want to ride it anywhere if you have to tote a can of ether with you wherever you go. I have an extra car battery that I keep charged, and I just hook it to the motorcycle battery with jumper cables - Positive on Positive, and negative on negative. I find this much easier than trying to keep the M/C battery fully charged for working on it. Just be more stubborn than the bike, and eventually you'll win!

 

FWIW, after trying to start this darn XJ for an hour last night, I finally walked over and fired up the 919, just to hear a freakin' motorcycle run! Fuel injection ROCKS!!! First flick of the button, and it's running like a sewing machine.

 

see i am having roughly the same problem except that mine with run continuously if the choke is at full. but when i turn the throttle it will raise to 2000 rpm before deing out. i thought i was running to lean and to much air was getting through. ive done a full clean of the carbs.and my petcock vavle works

im continously playing with it, and ill let you know what i find maybe my problem is related to yours ill keep you posted. good luck let me know how you fix it.

all the best

 

First off you do need to clean and inspect the float valves, and check the float heights, both statically and then with fluid.

When you've had the carbs off, did you bench sync them before reinstallation?

Did you "break the rack" when they were off?