XJ550 carb help

I got the carbs from my friend's 82 550 Maxim fairly cleaned and reassembled yesterday. I didn't break the rack, but I did dip them for a couple hours and spray them out. I know, I know... I should break the rack and pull the shafts, but I'm not comfortable with that, especially not on a bike that's not mine.

Anyway, before the cleaning, it ran only with the choke on, and raced badly. Not sure what kinda RPMs it was turning as the tach cable is MIA, but it sounds like 4-5k. When I got the carbs off, they were FUBAR. Mains were filthy, #1 needle was seized in the nozzle with crud, and the #1 and #4 mixture screws had to be taken out with my impact driver. The PO replaced the float needles and seats with aftermarket ones, obviously didn't even really try to clean the carbs, and most likely didn't set the float levels.

I installed Dynojet #140 jets and their needles at the request of the owner, since they came with the bike. Set the mix screws to 3 turns out as the Dynojet instructions called for/ I replaced the rack, and tried to fire it up... almost as bad as before. Now it'll run with the choke off if I give it throttle, but won't idle at all without the choke, and still races with the choke. Tried turning the mixture screws out to 3.5 and then 4, it seemed to help a bit, but not much.

Obviously I need to clean the carbs more, and set the float levels, as I have no clue where they are... but I know the petcock passes fuel. :roll: Engine side carb boots are new, the airbox side boots are seated and look good. Is there anything else I'm missing to fix the lack of idling, besides the universal answer of "break the rack and replace the shaft seals"?

Also, what would cause the racing with the choke circuit on? My 700 barely needs the choke, and will stall with it on after about 30 seconds of running, so I wouldn't think it should be adding enough fuel to cause the RPMs to get that high. At first I thought someone had dinked with the idle screw to try to mask dirty carbs, but the butterflies are nearly shut with no throttle. Symptoms sound like there must be an air leak somewhere...

 

First off, float levels are CRITICAL and can cause all sorts of weird symptoms. So if those haven't been set using fuel and the "clear tube" method, then start there.

You said the carbs were fubar nasty. Pull the circlip and nylon washer off the ends of the throttle shaft and inspect the two of the eight seals you can see. If they're toast, you can be reasonably sure the others are as well. If they're ok, it's no guarantee as to the others but it will tell you if they're bad for sure.

"Dipping" the carbs is not a good idea if they're not going to be fully disassembled, the throttle shaft seals are trapped in there. If they get loaded up with your "dip" it can cause new problems, especially if they were marginal to begin with.

-Float levels

-bench sync

Then it should at least start.

 

I knew there was a possibility of the dip trashing the shaft seals, and told the owner as much. We agreed to risk it, since if I disassemble the rack they should be replaced anyway... might as well take the chance since he's not paying for labor. I took the chance with the easy way when I got my 700 and won, so I figured I'd press my luck for 2. :lol:

As asked in the other 550 carb thread, what does one use for 'nipples' off the Mikuni bowl drains? Or do I just find some tubing that press fits into the drain hole?

 

(See other thread.) Any conveniently-sized plastic hose fitting; like I said I don't remember if I got mine at the auto parts or stole it from my Mity-Vac kit.

Believe it or not, there's a "factory" tool which is a little brass fitting with an o-ring but it's actually a hassle to use so I use the plastic fitting.

 

Bigfitz, is it one of the fittings from this kit? I was thinking about getting it but want to make sure the right fitting will be there to help me with my float test:

Mityvac

 

I don't remember. I "whittled" it down from a little plastic vac fitting, I honestly don't remember if I yoinked it out of the MityVac or picked up an assortment of plastic vacuum fittings from the "HELP" rack at the auto parts.

All you need is an appropriately-sized tube of any sort to jam in the drain hole, (something a tad more substantial than a ball point pen barrel.) Go look at the auto parts store; it shouldn't set you back more than a buck or two.

 

Well, I managed to get it running last night. We wound up replacing all 4 pilot fuel jets, I had to use an EZ -out to remove them, so I figured that was a good sign they were the culprit. With new jets, mixture needle spring seats and O-rings, and a couple adjustments, it idles and runs great once it warms up.

Surprisingly, all the float levels were very close to correct. 1/8" I.D. clear hose and the tip from one of those clicky Bic pens, with the end that goes into the pen barrel flared out a little, works great.

Only remaining issue is the RPMs when the choke is on. It's finicky to start at anything but full choke, but I have to quickly knock the chock lever down to 1/2-1/4 once it starts, or it 'idles' at 4-5000rpm within a few seconds. The only engine-related checks we still need to do are checking the valve clearances, and properly syncing the carbs, so I'm a little lost why it would be doing this.

 

Carb sync. But you need to do the valves first, or you'll have to go back and re-sync after the valve adjustment anyway.

 

I know they both need to be done, and in order. That's why I said we still needed to check the valves and sync the carbs.

It was more a question of whether either of those things could be causing the super-high-idle with the choke on.

 

Yes. What will happen is if one carb is high enough to start to come "off idle" and lift the slide, it will pull it way up.