The bike that just won't cooperate...

This has been discussed a thousand times but I just can't get the information through my thick skull. I've read through a thousound threads, posted about it before, tried just about everything. I'm at the end of my wits with this bike. 1981 Xi550

I'm trying to get my bike tuned in and it just wont idle. It's either idling at 200 rpm then stalling, or the idle hangs at 2-3 grand, there is no in between. Its hard to even keep it running around 1000rpm by hand.

Bike Starts just fine, revs up to about 4-5 grand with choke. Turn off the choke and it drops to 2500rpm. I very slowly back the idle screw between the carbs out and it does nothing for about 2-3 turns and suddlenly the idle drops down to very low where it eventually stalls. Turn it back in and it will creep up and as soon as you blip the throttle it gets stuck back at 3 grand. The bike runs great going down the road. Lots of power.

Here's what I've did so far.

The carbs have been off and cleaned about 10 times so far to the church of clean (yes, I'm that guy)
-Broke the rack Cleaned thoroughly.
-Replaced all throttle shaft seals
-Replaced #3 carberurator Broken Float pin
-Replaced all needles and o-rings
-Replaced all enrichment plunger Hats
-Cleaned all vaccum slides and clunk tested them
-Cleaned the pilot circut and emulsion tubes well.
-Bench Synced carbs
-Wet set all float levels to 2mm +/- 1mm
-Adjusted all mixture needles to 2 1/2 turns out
-Replaced #4 mixture needle and tapped hole (threads messed up)
-Replaced all mixture needle o-rings and washers

I removed the head, removed all valves and checked the valves and springs.
-Lapped the valves in
-Replaced valve seals
-Replaced Intake boot gaskets and checked boots
-Replaced head gasket

-All Valves shims are in spec.
-Fuel tank is clean and petcock works correctly.
-airbox with filter is installed.

-Good coils
-New spark plug caps
-New spark plugs
-Good wires
-all plugs are in decent shape, doesn't look lean or rich.

The bike runs exactly the same as before I removed the head and broke the carbs and did the throttle shaft seals. so I don't think that I messed something up after I did the top end.


I'm trying to sync the carbs with a single vacuum gauge using the old school method. It's hard to get a consistent idle but I have them all very close to 20hg at around 2-3 grand.

I can get it to idle at partial choke at around 1000 but it hangs BAD when you rev it. I get consistant vaccum readings of 10hg on all 4 carbs but I don't think I can trust that as the mixture is diffrent with the choke. I would like to buy a carbtune tool but I already have about 800 dollars in this bike and i really dont want to spend any more if it's a lost cause.

I don't know what else to do! I've been over the bike with a fine tooth comb 30 times and either I'm missing something or i'm just not being precise enough..

 

Well, some things come to my mind right away:

1. I would ONLY use the Morgan . I wouldn't try to balance four carbs by setting only one at a time. You're trying to BALANCE them....

2. Have you checked for vacuum leaks at- the boots, the throttle shaft seals even though you already did them, the boot-to-manifold gaskets, etc....

3. Are you absolutely positive that you didn't accidentally swap some of the air jets?

4. Diaphragm holes?

 

1. I agree with that, I'm just trying to hold off incase I have to take it to somebody, they can tune it properly and I can use the money to have them do it.
2. Yes I sprayed carb cleaner and made sure there are no vaccum leaks.
3. The jets were removed and cleaned one at a time.
4. If you mean holes in the diaphragms, They are like new, no pinholes.

I just took it for a 12 mile ride and it ran good. Still had to help it at stops but took longer to stall. i noticed if you let it stall, it was VERY hard to start. When Running down the road the idle won't hang until you let it sit and idle

 

You're gonna pay to have them do it.... You get the bike done, your money is gone.

Or

You buy it yourself, do it yourself, your bike gets done, you own the tools, now you can do it for others.... Sync anything, Make a few $$, too....

 

almost sounds like a low compression problem. Have you checked the compression of the engine?

 

Re-visit the pilot wells and jets. Did you spray carb cleaner through each one?

Gary H.

 

Check to make sure the enrichment plungers are properly seating in the plunger well. The plungers may have developed a wear ring where the plunger meets the plunger seat. IIRC this involves using a golf tee to burnish the seat smooth and also dressing the matching enrichment plunger end as well. This may explain why your idle only drops to 2,500 once closing the enrichment (choke) circuit. If the plungers aren't seating properly you might be introducing fuel through enrichment when you think it's closed. Then when you run out the idle screw to lower rpms, you end up over-correcting. Just a thought.

 

are you sure that the throttle shafts are closing, fully, onto the idle stop screw, could the throttle cable be sticking , after you blip the throttle, and get the high hanging idle,
if you push down on the throttle linkage, does the idle drop?
maybe the shafts are stiff ,or cable is stiff, not allowing the butterflies to close fully
stu

 

Have you tried with the throttle cables disconnected? And just working the throttle with your hand or a screwdriver if you have big hands.it really sounds like a cable sticking.

 

I'll look into the cable, but it operates freely but the throttle snaps shut with alot of force and I checked the butterflies when I bench synced the carbs.

Everything in the carb is surgically clean and has had a lot of carb cleaner sprayed through it.

I inspected the enrichment plungers but I'll check them again.

 

this statement concerns me s I will ask

when you had the slides out and the main jet out as well as the asperator tube did you spray carb cleaner into the main air jet and see it coming out the holes in the passage where the asperator tube goes?

when you had the pilot jet out did you spray down thw pilot air jet and see cleaner coming out the location where the pilot jet goes as well as into the mixture screw passage and the little holes where the butterfly plate is?
same with the enrichment circuit?

if you did then thay are clean

make the baby bottle sync tool 10$
its easy and will get you into the ball park

do you know what syncing is actualing syncing?
read and you will understand why 1 vac meter is the wrong way
TALKIN' TECH: Various thoughts on various issues

Because YOU'RE NOT "SYNCHING" THE CARBS!


$5 tool
http://www.xjbikes.com/forums/threads/5-carb-sync-tool.4191/


How To: Make a 2 bottle synch tool

 

A single vac gauge will do the job if; the gauge has little needle flutter, and the operator writes down the baseline vacuum reading that he is using as a target.

 

there is also a thread on how to do it by ear,
it is just a matter of having the skill set to do it that way

 

Mr. Massey did a good write-up for using a single gauge. I use four gauges...it's easier.

Gary H.

 

Okay update:

Got the carbs ball park synced. very close. Still having idle problems though. I'm not getting, is I can make the bike sit the and idle smooth all day long if I crack the throttle a little bit by hand, doesn't hang or anything.

Plugs, after doing "chop" test
:

Now, If im correct the idle knob is doing the same thing I'm doing with the throttle, right? Keeping the butterflies open a certain amount. If I set the Idle screw to where It has the butterflies open to the same spot where I would hold it open by hand( (only a few turns in), the idle zooms up like it has been, and takes FOREVER to drop back down to the point it stalls. If I back the screw back out, the engine slaps right back to idle as fast as it revs up, but it still stalls. I figure thats because it is shutting the proper amount, but somethings still up with the idle circuit. I'm damn sure its clean, and the jets are right (unless someone messed with them before I got the bike, but it all looked untouched)

I took the time and did a proper compression and leakdown test. Here's the results:


I just did the top end and multiple people told me to just put it back together and run it and see if the valves fix it, or rings free up or something. Shoulda just did the rings while I had it apart.
I did a leakdown test, and at 25 PSI, I had zero leakage through the valves, but feel air coming out of the oil fill hole. The tester didn't exactly tell me much in terms of % of leakage, but I know the valves are good.

So the big question is with the condition that my engine is in currently, is it a lost cause trying to get the thing tuned up till I get the compression up? The bike has 16000 miles, which I find hard for it to have compression issues, but it seems like it's been pretty neglected in its past life.

I'm trying to get it going but paitence is wearing thin, and pretty much every bike shop around here has told me that they will not touch these older bikes as they are just getting too rough. So it's up to me or nobody I guess haha. Thanks for everyone's helpfulness and paitence.

 

Your pics aren't showing up. Many photo-hosting sites are blocking links to other websites (because they are really just wanting you to store photos there to use their printing services). What hosting site are you using?

 

Now on to the trouble. You have an hanging idle, which is most often a symptom of a lean condition caused by an air leak.
I would like you to describe your carb cleaning procedure.
Did you follow the methods that are explained in The Church of Clean?
What solvent(s) did you use?
Did you dip the carbs?
Did you replace any of the throttle shaft seals or any of the o-rings?
Did you inspect the intake boots for cracks?
If you removed the air jets; did you put them back into the holes that they came from, or did you follow the picture that is in the service manual?

As for your big question: It runs. You have a viable motorcycle., but there is still work to be done.
16,000 miles over 30(ish) years means that it has sat for a lot of those years. The most likely cause of low compression in a bike that runs, but has sat for extended periods, is stuck rings. Compression will come up over time if that is the case.

I agree that you could have pulled the cylinders while the head was off, but there is no sense kicking yourself for doing what you did. Unless the goal was a full refresh of a low-mileage engine (a route that I would not take) then you made a sound decision.

 

Not to sound critical are you running stock airbox and filter? If you are not it could cause some problems. Or maybe i did not read it right .

 

Yes stock airbox and one of those foam filters chacal sells

 

Pods won't cause a hanging idle.

 

I did not dip them.
I have cleaned the carbs about 5 times so far, using 1-2 cans of cleaner each time.
Jets were put back where they came from.

What I did:

I thoroughly cleaned the carbs the first without breaking them apart just by using an assortment of brushes and spray carb cleaner, paying extra attention to the idle and enrichment circuits. I followed the church of clean.

Put it all back together and had problems with the floats sticking and hard starting. I went back through and replaced all the needles and adjusted the floats. Broke a float tower in the process and tried to repair it. Adjusted all the float levels and cleaned the carbs fully once again.

Put them back on and the bike still didnt run right, (chacal was very correct when he said do it right ONCE) So I fully broke them apart, cleaned everything again, replaced the throttle shaft seals, carb plunger boots, idle mixture orings and washers, needle seat orings, and replaced the carb body with the broken float tower and thouroghly cleaned it before installing. Sprayed carb cleaner through every hole and reassembled them. Made sure the carbs were all aligned with the face of a level and bench synced them.

Put new intake boot gaskets and inspected the boots (like new) and lapped the valves(seal beautifully) and made sure they had the correct clearance. Installed the carbs, set the idle mixture screw about 2 1/2 turns out. synced them and drove it about 30 miles. Used carb cleaner to check for leaks. That's where I'm at.

All the picture is, is a chart of my compression test with engine cold.

Dry: 1-75psi 2-75psi 3-80psi 4-80psi
Wet: 1-90psi 2-95psi 3-95psi 4-105psi

Hot readings aren't much different.


Thanks

 

Compression is to low. XJ550's should be around 125psi/cylinder. Low compression leads to incomplete combustion which is most likely why it's running poorly

 

Low compression won't cause a hanging idle.

 

Will low compression cause a low idle/stalling condition?

I'll try to explain this as clearly as possible. There's 3 scenarios.
As I said earlier, it only hangs when I turn the idle screw in to where it "should run at the correct rpm"

But when I do that it causes the bike to run like this:

Bike will be running at 500rpm barely running. I turn the idle screw in SLOWLEY, and it does nothing (idle should be creeping up as i turn the screw in right?) Until I hit a few turns in and the engine takes off and hangs at 3grand. I can back the idle screw off maybe 1/4 turn and it drops back to 200-500 rpm and stalls out. It acts like there is no middle ground between 500 and 3000 rpm.


Scenerio 2:

If I keep the idle screw backed out, it does the 400-500rpm idle problem, but does NOT hang at all. You just have to help it run at stops.

Scenario 3:

I hold the throttle open by hand just a tiny bit to where it idles at 1000grand. Runs how it should. If I turn the idle screw into where it would be holding the butterflies open the same amount it does scenario 1.

I'm lost

 

so in scenario 3 you use throttle to go to 1K rpm then when you turn the screw in to hold carb 3 at 1k rpm it jets up to 3 k rpm when you release the throttle grip.
when reassembling carb bodies it is my understanding that you align on 2 axis across the front of carb throats and across the top where the diaphrams sit.( I have a spare set on my shelf where#1 body is 1/8 inch lower that other 3 bodies)
it could be you miss alined the throttle shaft linkages or assembled the connecting parts incorrectly
look at what changes from the pull of the throttle cable to the holding up of the throttle linkage

 

550 engines:
Minimum: 100 psi
Standard: 121 psi
Maximum: 135 psi
Max. variance between lowest and highest: 14 psi

your readings are low and 15 psi different

read this thread
http://www.xjbikes.com/forums/threa...l-1-4-high-valve-clearance.83115/#post-500621
could be stuck rings
need to figure out idle problem first

 

I aligned them by putting the engine side on the face of a (straight) level and putting another level on the intake side, the lightly clamping everything down with light pressure. Then I installed both rails.

I double checked the straightness again before I put them on and it looked pretty good. Everything looked pretty even when lookin through the carbs at a light. After bench sync. When the throttle was closed completely there were no light gaps. I'll have to look into checking it with the diagram side though.

 

If the bench is good, the floats are good and there are no leaks then it's this...

Gary H.

 

This is interesting, I aligned my rack the same as buyerz78 - intake and output sides squared up.
XJ550H, it is intriguing that you have a rack that has one carb lower than the others, seems the rails should align the 'up and down' - curious what others think . . .

Back to Buyerz78 issue; when you are turning the idle screw and there is no apparent rpm change have you tried blipping the throttle after every 1/4 turn or so?

 

A thick piece of glass large enough to cover the rack should be easier.

Gary H.

 

Well yes, I actually used a granite square set on the work bench, placed the intakes on it then used a 2x6 (notched for throttle linkage), to apply pressure to the carbs to square them up against the granite.

What has my curiosity peaked is the idea that the carbs also need to be squared up top to bottom (as I believe XJ550H was inferring to).

 

Unless the rails are bent, the carbs should all end up at the same height and depth. There really isn't much wiggle-room in the holes for the machine screws.

 

when i take them apart I will find out why #1 is lower the only thing I did was remove the bowls to see what I was in for as far as how gummed up they were. the po was inside of them for sure. not a good thing.