Please help! 550 problem!!!

Ok, so let me fill you in on the problem.

My 82 xj ran fine a few days ago, after purchasing the bike less than 3 months ago I cleaned the carbs and bench synced them and the bike ran fine afterwards. A little while ago, the carbs started leaking fuel into the airbox... so I figured something was making the floats stick (still haven't put a fuel filter on yet but it's coming)... So, I took the carbs apart again and sure enough there was something stuck in the needle hole... and I replaced all 4 o-rings because they were looking bad and I thought that would be a good idea. I checked and all the floats are set evenly, and everything else seemed fine, so I put the carbs back on the bike and changed the oil. I started her up, and she ran beautifully with no leaks. Now here is where it gets weird.

I few hours later, I come back to start her up, and she starts fine, but then she slowly seems to loose rpms... even with full "choke" on. I give it some throttle, and it drops a bit before kicking in and the rpms jump up like they should. So, I come back a few hours later, and now it won't even start up... weird. So, I decide to replace the spark plugs with brand new ones a few days later (today)... starts up fine, with full choke on it's idling a little above 2k but I figure I'll let it get warmed up before I take it off. I pull the throttle a bit and it kinda hesitates and drops slightly right before the rpms rev up. So I let it idle for a few more seconds and it starts to lose rpms. So I pull the throttle and it dies. I start it back up and it's barely idling, and when I pull the throttle, it dies... everytime. After a few more times it gets consistently worse, and now it won't start at all...

I tried turning up the idle adjustment, and I made sure the pilot screws were about 2.5 turns out from bottomed out since I haven't had time to tune it since replacing the o-rings and the spark plugs... any ideas on what I should do? Does any of this sound like a problem that is identifiable by my symptoms? Thanks for your help, I need to fix this soon too because I have to use it to get to class this semester :|

 

what are the plugs looking like? sounds like you may be fouling plugs... the petcock on is set to 'ON', not 'PRI' right?

you might be getting hydro lock from gas still getting into the oil, just a thought.

 

Yeah petcock is set to on, but I believe the floats are holding the gas level correctly anyway, which is also why I doubt any gas is getting into the oil anymore. When I changed the plugs they were pretty dark, but I figure that was just because of the leaky floats at the time... the new ones still look new because they were just put in.

 

Strange problem. did you make sure the choke cable isn't getting hung up and keeping it open somehow? it does sound like she's getting too much fuel but will be hard to tell until you get the newness off of the plugs...

 

You think it's getting too much fuel? Why would that cause it to die when the throttle is pulled?

 

if the mixture is too rich, from what I've seen you'll have a boggy motor... if the choke was hung up a slight bit that would be giving it more gas than it could probably handle at the time, that's all...

 

When properly rebuilding carbs all those O-rings should have been replaced the first time you had them apart. Taking shortcuts only leads to having to re-do what you have just done. Since you just bought the bike , the fuel system is one of the first thing to get right. Clean the tank, clean and rebuild the carbs, install a fuel filter. While you are in there adjust the valves and replace the carb boots if needed. Follow the procedures to the "T" and it will run right the first time and most likley you won't have to do it again for awhile. After it runs good start going through other things like brakes and suspension. Then after you are familiar with all those thinge you are ready for a ride.

 

Well the choke is definitely not getting hung up on anything, it moves just as it should... and thanks for the advice mlew but non of that really answers my problems at the moment. I just had the tank cleaned, lined, and painted, the carbs were rebuilt shortly before I bought them and they are damn clean. The only thing I haven't done yet is install a fuel filter because I'm trying to solve this problem first. If it sounds like it's too rich should I turn in the pilot screws a bit? Would that stop it from starting?

 

Its good you had the tank cleaned. Reading the problems you have I would bet that your pilot jets are pluged up and/or the carb slides are sticking. Pluged pilots = hard or impossible to start. Sticking carb slides= dies and sputters when throttle is opened. Next thing to do is remoce the carbs, clean the pilots, check the slides and install a fuel filter. If the carbs are clean the position of the idle mixture screw won't make the engine not start. It will just not run well. You have them a 2 1/2 turns and thats a good starting place.

 

That sounds like a good plan, does that have anything to do with it loosing rpms during idling? It's never done that before and it started loosing those rpms before I even opened the throttle.

 

Yes, the pilot jets have really small holes. It does not take much dirt to clog one. If the fuel has stuff floating around it will get sucked in the jet and clog it. You most likley won't need to replace anything, just remove the bowls and pilot jets. Find a small wire that will go through the jet and "poke" it out. I'll use a single wire from a small wire brush, others have used guitar strings.Spray some carb cleaner through to get the rest out. Install that fuel filter to keep them clean. Check to see if those carb slides are free moving also. Search the forums for "clunk test" and read up on them, they might need some work. While they are out do a bench sync on them.

 

Alright, I appreciate the info. I noticed you live in Apex, if for some reason I'm still having problems after I address the issues you listed maybe you could help me? I live up near NC State.

 

Hold on a sec. We already know there have been float valve issues.

Have you checked the float heights using fuel and the "clear tube" method? The Mikunis on the 550s are VERY SENSITIVE to float height adjustment, trust me. That could be your entire problem.

Get an inline fuel filter fitted pronto. No sense having crud complicate your tuning efforts.

Unrelated but important: How many miles on the bike? Have you checked the valves yet? How OLD are the tires? (check date codes.)

HAVE YOU CHECKED THE REAR BRAKE SHOES YET???

 

No I haven't used the clear tube method but the floats are all lined up and visibly look identical in height. I never had any problems float wise until that crud got stuck. On another note, just got new tires but haven't checked the rear brake though it is on the list. I just got done cleaning out the jets and it passes the clunk test with 4 loud clunks. I fitted a fuel filter on the fuel line and put em back on the bike, so now I'm just waiting for the fuel to fill everything to start it up.

 

Visibly checking the float heights won't do it. You've got to be in the middle of a 3mm range; dry setting isn't accurate, it just gets you started.

Trust me here; a 550 with one wacky float won't run right; two and it will make you nuts.

You've had the floats apart. You HAVE TO confirm (and adjust) the heights, period.

Or screw with it forever trying to compensate.

 

Fitz is right its a little messy but u have to do it to get it running any where near smooth on the 550's