Help me with these carbs?

1982 xj550 maxim:

So I just recently did a big cleaning of my carbs, and they came together nicely. I was able to get the bike to start today, and no more leaking gas.

The bike idled great the first few times, but only with the choke on. I wanted to adjust it so it could idle without the choke so I started making some adjustments to the idle adjustment, and the air/fuel mixture screws.

I do not have the equipment to bench sync the carbs, so I was trying to keep everything how it was set when I got it, but that's not happening now that I see it needs the choke.

If I screw in the air/fuel screw, aren't I making it more rich?

Also, one symptom I'm having is that I'll twist the throttle a bit, and it takes a long time for it to come back down. My tach cable is broken, so I'm not sure where it's at, but by sound it's stays way high for like 20 seconds, then it will fall down to the idle rpms. I've never dealt with these diaphragm type carbs before that use vacuums for the throttle control... Are they sticking open for some reason?

Any insight would be great!

 

1. you don't need anything special to bench synch lots of threads on how to do it with a piece of 3x5, a paper clip or visually setting them even. cleaning them will change the sync so setting them to what they were is unlikely to work.
2. screwing the mixture screw in leans the mixture, out makes it richer.
3. hanging throttle is often from a vacuum leak. how are your carb to head boots and your butterfly shaft seals? also did your carbs go clunk if they didn't you need to go to the whole nine yards to the church of clean

carbs clunk: http://xjbikes.com/Forums/viewtopic/t=1 ... art=0.html

whole 9 yards: http://xjbikes.com/Forums/viewtopic/t=2 ... n+own.html

church of clean: http://www.xjbikes.com/Forums/viewtopic/t=14692.html

 

Hmmm... regarding the "clunk," wouldn't it "clunk" with the spring and diaphragm in? When I had them out, I pushed each piston up, and it dropped but only slowly. Or is that how it's supposed to go when the diaphragm is in?

my carb to head boots have some surface cracks... but i didn't think they were leaking yet. I'll spray them to see. And I don't believe I had butterfly shaft seals

I'll pull them again... man I hate that air box.

 

The piston slides in the carbs should just drop right down and go clunk when you have the carbs apart. When you put the hats back on its a different story. The diaphrams and springs will not let the piston slides clunk.
If they are coming back off and you have the tops off, polish the slide bores and see how the pistons drop in. Also bench sync with a strip of a business card. You will need to do a complete sync later and that means you'll need to verify your valve clearances. In any case good luck and report back on your progress.

MN

PS. you will need to check those shaft seals. Pop an e clip off of one of the outer carbs and see the condition of them. If they are hard and cracked see chacal for replacements.

 

So, while the carbs were still in the bike I "clunked" each slide, and they all dropped pretty good and heavy. I also sprayed wd-40 all over my carb to engine boots to see if there is a leak there, but I couldn't see any.

I did actually have the butterfly shaft seals, I had just forgotten... My mind was toast that day. Is there a good way to test those, or is that mostly a visual test? And thanks!!

 

Again, slides shouldn't "clunk" when the carb is assembled. The air metering port in the slide actually dampens the spring force and makes the slide smoothly slide down.

With the carb hats off, and only the weight of the slide pulling it down, it should go "clunk" when dropped from the top of the bore.

I recently assembled my turbo seca carbs after a thorough rebuild. I polished the bores and the slides went "clunk" when disassembled. After assembling, I noticed that 3 of the four would still clunk, the fourth moved smoothly. When I took off the hats again, I noticed that the diaphragm hadn't seated properly on those 3, and that's why they clunked. The loner was actually correct, and after re-seating all of the diaphragms, all of the slides act the same way.

Sticking slides can cause a hanging idle and a lean condition, because if they don't drop when you close the throttle, the air moving through the venturi actually slows down, creating less of a pressure drop, and just drawing less fuel in through the main and idle circuit.

 

You don't 'see' if there is a vacuum leak, when spraying the carb to head manifolds. (WHEN OPERATING TEMPERATURE HAS BEEN REACHED!) - you spray all around them, whilst you have a consistent 'idle' (it doesnt matter how high, or low - just 'consistent'), and you hear, an increase in rpm, above the current idling rpm (and maybe see on rpm meter) while you are spraying. If you notice an increase in rpm whilst you are carrying out this spray test, all around the carb to manifold head rubbers, it is indicative of fissures, cracks, which are causing vacuum leaks, and therefore one of the possible reasons for high idling at OPERATING TEMPERATURE.
If you do this test and find this is the case......the rubbers can be 'repaired' with silicone sealant, and reinstalled. (see my earlier threads)

 

So I sprayed my boots again, while at a constant idle, and I went from maybe 1200 rpm to 2000 rpm after spraying. I assume my boots are bad.

I saw the pictures in one of your posts... Did you just coat the outside with silicone? What did you use to clean them first?

 

I suspect a compound problem; not just a potential vacuum leak.

Mikuni carb: http://xjbikes.com/Forums/viewtopic/t=31061.html

How far apart did you have the carbs? (Reference exploded view linked above.)

Did you "wet-set" the float levels? For each carb, individually? This is critical.

When doing a bench sync on the Mikunis, it's much easier to use the relationship of the butterflies to the tiny bypass port holes in the top of the throat than it is to try to "gauge" the drag on a feeler of any sort.

By all means, seal the cracks in your intake manifolds. But also check and see if they actually go all the way through. (Flex from inside with fingertip.) Your problem could be throttle shaft seals, or as simple as rock-hard vacuum spigot caps. The spray could have gotten in via those avenues as well, you won't know until you check and see if the manifolds are actually cracked through. If they're not, the leak is elsewhere.

Once you get this sorted, you will have to do a running vacuum sync with the YICS blocked. You're not going to be able to "earball" it, trust me.

DIY tools for that can be put together for very little outlay.