Xj running problem HELP!!!!!!!!!!

right here goes i have an x reg xj550, just put a new battery on, changed the rectifier(2nd hand) and cleaned the carbs. The problem is the bike will struggle to start when it does start it runs very lumpy, sometimes it pops n backfires not all the time though. if keep the revs around 2000rpm it will run forever altho sounding a lil rough let the revs drop and the bike will die sometimes needing a jump start from another battery to get it going again. On occasion i have had to hold the throttle fully open just to get it to tick over im really scratching my head over this now. could it be the alternator bushes? any ideas?

 

Sounds like a lot of things. Not wanting to run unless held over 2K RPMs and not wanting to start unless jumped seems to indicate that the battery you've got in the bike is shot. I'd replace the battery for starters (no pun intended) and go from there.

Reasoning behind my suggestion: the charging system is idle until the engine RPMs come up to around 2,000 RPMs. Below that you're running off the battery. If your battery is no good, there's just not enough juice to share between your ignition system and the lights.

 

When was the last time the carbs were off and cleaned??
You have a volt meter hooked up to your battery and make sure you have at least 13 volts plus when running above idle around 2K . If your battery is bad you won't have enough power to run the Ignition System.

 

bike has just had the carbs cleaned and a brand new battery

 

Check the voltage then and see what you have

 

What does "x reg xj550" mean? How many miles are on the bike? After the carb cleaning were the float levels checked with FLUID; and were the carbs bench-synced before you tried to fire it back up?

 

You shouldn't need to jump the bike if the battery is fine/new. You've got something going on there that needs to be remedied. If you're confident that the battery is all charged up and the bike still doesn't crank and start on it's own, then I'd remove and clean all the battery cables--both positive and negative.

What voltage does the battery read before cranking? While cranking? Held at high idle?

I suspect that the popping/backfiring is caused from the ignition system dropping out while running. This will fill the exhaust with unburned fuel that will eventually reignite when the ignition system returns. This will also flood the engine if it stalls with the throttle open and make it hard to restart.

 

before cranking the voltage sits just over 12 and around 14 at high idle and drops to between 10 and 12 while cranking

i put some washers between the casing and the alternator brushes to move them closer and give better contact and it did start with out a jump start but still ran very lumpy carbs are coming back off today but i really dont think it has anything to do with the carbs as no settings have been changed and the bike ran beautiful before this

and im sorry but the milage is totaly irelivant to the problem im having so x reg xj550 means its an x reg xj550 :evil:

 

Unfortunately, we're mostly North American here, so help us out and tell us what year an "X reg" vehicle would be.

 

How much did you shim the brush carrier? They shouldn't need it if your springs are in good shape. I would encourage you to change the brushes rather than shim.
Is it possible you are putting too much pressure on the brushes?
Another issue may be your wiring. Did anything get pinched upon re-installation?
Clean the carbs anyway, they can always use it.
And +1 on Maximum, what does x reg xj550 mean?

 

1981/82

i put in a washer around 2mm thick, all wiring seems fine and the carbs are clean and set up correctly thats y it has me so baffled

 

This really sounds plausible. I also agree that shimming the alternator brush holder is not the way to go. It sounds to me like the bike is having a hard time running off the battery below 2K rpm; this could be exascerbated by carburetor issues.

The reason I asked about the mileage on the bike had to do with things like valve clearances and/or the possibility of worn alternator brushes.

 

can you not use a spray bottle and see if this is a fuel problem before taking off the carbs? The battery and alternater seem to be working. Maybe the pilot jets got plugged. Mine will start right up if spraying a little gas in even one carb. Might be just starving for fuel. Are all the plugs firing?

 

If you have a propane tourch on hand, just add raw propane to the air box and see if it runs. The propane will burn just like gas and or richen up the intake charge at idle. Its also a good way to see how lean you are at idle. If your bike is running ok but not great idle quality. Add propane and see if the idle picks up, if it does your lean. I have found even after cleaning the daylights out of the carbs you may not be able to get enough fuel at idle. That means taking them back off and going through the smallest pasages with fine wires to dislodge all junk in there. I finally have the carbs on my Black 750 running right and I can actually adjust the idle mixture screws out enough to make it run rich enough so the propane will not make it idle up. Hope that helps

 

If you pull the carbs off again i would double check your idle jet circuit. Make sure the jet is clean and the passageway. then check the setting on your mixture screw (if you can)