Carb syncing. WTF>!>!>@ Help PLZ

So here is my situation:
Followed instructions to the T:
-Pulled carbs and cleaned everything according to "In the house of clean"
-Bench synced the carbs by placing a small feeler into the butterfly opening and clamping all of the butterflys to the same shim.
-Checked valve shims (replaced 2 intake shims on #3 and #4)
-Checked float height using the clear tube method
-Made sure my carbs went "clunk"
-Spun my idle adjustment screw 2 and a half turns clockwise
-Tightened down my air/fuel screws and unscrewed them 2 and 1/2 out
-Reinstalled everything on bike properly
-Made a homemade manometer
-Stuffed the hell out of the YCIS tube using oil soaked t-shirts and replaced the bolts
-Pulled all of the vacuum boots off the intake boots and hooked my homemade manometer to #3 and #4.
-Synced them (moderate increase in idle; I turned it out 1/2 to make it normal again)
-Synced #1 and #2 together (noticed fluctuations in the vacuum when they got closer to one another)
HERE IS WHERE IT GOES CRAZY+++!+@
When I start up the bike with the manometer inserted into intake boots 2 and 3, 2 attempts to suck the ATF straight out (WAY OFF)
-As I get closer to the sync, the idle raises high; I mean WAY high. It seems like it is going to explode if I dont turn off the bike.
-Turning the idle adjustment screw is not effective at all at this point (no matter what I do)
-Checked choke cable. Choke system is fine, all of the caps are down in their seats nicely and not raised.

The idle goes down if I ride it and hit the brakes; but if I pull in the clutch, the high idle returns with a passion (REVVING LIKE CRAZY). What in the world could be the deal? I have tried to apply diligence, it just seems that it is fruitless.

 

This advice is for stock airbox, carbs, and exhaust. If you have pods someone will be along shortly to add that advice.

Did you have all 4 vac caps off at the same time when you did the sync with only a 2 carb manometer?

If yes, then you gotta re-do the sync. You should only have the vac caps off the intake boots that you have the manometer hooked to. This is presuming you have a homemade two carb sync tool, not a 4 carb tool.

If no, then you need to start looking for air leaks in the carb seals, throttle shaft seals, intake boots, vac caps, etc.

 

Ok. Yes I had all of the caps off. I will try it with them on. BRB!

 

You're out of sync and probably over-adjusting.

First off, if you're using a "comparative" manometer (that only attaches to two spigots at a time) then the other vacuum spigots need to remain capped until it's their turn.

The idle is racing because at that point, one of the carbs is no longer running at idle, its slide is beginning to rise, and it will pull all 4 up off idle.

Don't sync by opening the various throttle plates; sync by closing them.

You want to turn the main idle knob down so the bike is running at about 1000~1100rpm for the sync; and then if any adjustments you make cause it to go up, turn it down a tad.

Make smaller "incremental" adjustments; 1/8 turn is HUGE.

"Blip" the throttle after each tweak, and wait for the motor to settle back down.

Be sure you have a box fan blowing on the motor for air circulation; also be sure the bike is fully warmed up before trying to sync. As in, went for a ride warmed up.

It actually sounds like you're close, provided you set the float levels individually and accurately. (That can cause this behavior as well.)

 

Still high revving. Idles just fine until they get "in tune" (turning the middle screw to set the sets). once the vacuum is right, the bike goes nuts

 

Its peculiar just because it only does it, RIGHT when they get in sync. Then all hell breaks loose in my garage

 

The "middle screw" is the #2 sync screw. #1 has one, #4 has one, #3 is adjusted only by the big knob. When you adjust #2, it brings #1 with it.

SNEAK UP ON IT. You're still opening the throttles to sync; you need to be closing, or keep turning the main knob down.

Go back and check the 3-4 sync again; maybe it's far enough out now to be the culprit.

Just making sure you understand: #1 will "follow" #2; #3 is home base, and #4 just gets matched to #3.

Set your mixture screws at 3 turns out instead of 2 1/2 then sync and see what happens.

You also might want to check up on your DIY YICS blocker; if it's not blocking all of the YICS passages from another, it can drive the process crazy; especially if a couple passages are blocked and others aren't. It's gotta be packed pretty tight.

 

Ok. I am going to try to turn out the screws three turns and repack the blocker... It sounds absolutely terrible... Just to confirm, here is the order that I have corrected them:
Given that there are 3 screws (1,2,4) and one main knob(3):

[]s[]s*[]s[]
1 2 3 4

First I turned 3 clockwise 2 and a half times.
I then synced screw 4 (successfully bringing 3 and 4 into sync with one another)
I move to screw 1 and complete it (again, success. Although it starts to rev, I am able to turn out 3 to compensate.
I start on screw 2 and hook up to cylinders 2 and 3 to read. WAY OFF, ATF almost gets ingested into my motor through the suction in cylinder 2. I start to bring them into tune, engine rev is directly proportional to the tuning. I get them tuned; my neighbor reminds me that her mother is sleeping. Star knob (screw 3) has no longer found relevance. It is fruitless to attempt to bring the idle down (short of placing the bike in first, letting it idle high, let off the clutch and cruise down the street with the brake partially placed down) However, if i pull the clutch in, the idle shoots straight to the roof and I am left looking like a moron. There has to be something wrong with my method.

 

You may have done your bench sync with the main knob too far out to begin with, thus running yourself out of "turn-down ability" just when you need it.

The big knob should be in at least about halfway, or as far as possible that will still allow you to bench sync.

That, or you're opening one of the throttles to far to sync it rather than closing it, and it's pulling the whole rack off idle.

Try my previous suggestions.

 

Ok... So, redo the bench sync, but this time try it with the idle set screw a bit further (tightened?) turned. that is plausible; given that it doesnt howl like a dog as soon as I turn it on following the bench sync

 

Every time you make and adjustment (after blipping the throttle like BigFitz said), adjust the idle knob to bring the idle RPM in the proper range (i think it's 1000 +/-50 for the shafties).

For example, if you adjust 3/4 to sync, and the idle rises to say 1500 rpm, lower it back down to 1000 using the idle knob, before syncing 1/2.

Remeber, idle is determined by the fuel air mixture reaching the cylinders, it isn't absolutely related to the throttle position. So if your sync is off, the "idle" actually is the result of the throttle being opened, with once cylinder compensating for another.

The blipping the throttle inbetween adjustments also helps set the adjustment screws. When you push down on the screws, you actually turn the throttle shaft, so blipping is important.

 

3 screws 1/2, 2/3, 3/4, you messed up your bench sync with 2 1/2 turns, way too much.
here's what to do
start it and turn the idle knob till it has some effect on the idle, you might have to turn it way in, now take the fuel line off, all vacuum caps on, start it and let it run out of gas, if it gets too fast use the choke, no more run away idle.
now put the hoses on 3/4 and set 3/4 screw with the starter only, only crank it 1 thousand, 2 thousand, 3 thousand, then stop, you should be trying for better not perfect. now do 1/2 with the 1/2 screw, again 1,2,3 better not perfect. now 1/2, 3/4 with the 2/3 screw, same 123, just better. you should be close now back off the idle knob a half turn and start over, then back off the idle knob and start it up. any time the idle knob has no effect, stop, somethings wrong. sounds like a pain but two and a half turns on a sync screw is about two and a quarter too much

 

You're advocating vacuum syncing on a stopped motor using the vacuum produced spinning it with the starter???

Just as a starting point for a RUNNING vacuum sync, right?

That's either brilliant or horribly wrong. I'm just not in a postion to say exactly which. I'm leaning toward brilliant.

TRY IT. I hear experience speaking...

 

well i kind of get the feeling Mr. Lohkie isn't real fond of trying to work on a hot motor reving that high and i don't blame him a bit.
granted it's easier with a set of gauges than bottles, i think that's what he made, right?
it shouldn't take long to find the closed butterfly that's holding the others open and get him close enough to do a running sync again without runaway rpm's.
i'll take a guess that 4 is holding 3 open and as he sets 2/3 they open to 3 and away it goes, varoomm.
you'd be surprised how close the sync is with just the starter.
Lohkie, if you have a tender or a charger, leave it on while you do all this, no sense running the battery down.
this is where having the valves set right really shows up

 

Actually, I do similar with my 4 tube Manometer - tap the starter and see which way the water wants to go at first. Make adjustments before even starting the bike. Water will quickly over-top a 5 foot rig.

Also, I found the BB sync idea on another site, which is a great way to at least get into the ball park quickly, with an easy-to-understand devise - - a BB in a tube.

BB Sync thread link

For bench sync, I found 2 narrow slips of printer paper, at 0.010 total thickness, gives me the correct "drag feel" while setting up the carbs.

 

i use the little holes on the top of the carb throat, half a hole showing is about right

 

I think you're way out of sync. As you're trying to bring 2 and 3 together one or more of the butterflies is closing down and holding others open. This is why the idle stop screw becomes useless to you.

Your 2 line comparative manometer only tells you how the two cylinders compare to each other. It gives no indication if they're closed tight, just right, or wide open. All you know is they are the same and you have no idea where the other two are.

It's not as straight forward as matching 1 to 2, 3 to 4, and finally 2 to 3. Each change affects all the others. You have to iterate through it several times.

The tool you're using pretty much requires that you start with a decent sync and takes a lot of patience. As far out as you are it's virtually hopeless.

You can pull the carbs back off, get a good bench sync and try again. Or you can go with a tool that lets you read all four. I suggest an inexpensive 4 gauge sync tool. It'll do the job well enough, is about the easiest to use and won't break the bank.

 

Some things I want to mention:

1. I thinks tskaz has the right idea here....sounds like only two carbs are being hooked up at a time.... SO, the other two must have caps over the vacuum ports when not hooked up to the gauges. I prefer the CarbTune gauges, as they hook right to all four at once and are very easy to read.

2. You're not going to get good results when hooking to 2 and 3 first. Do them in this order:

Sync 3 with 4 ( or 1 with 2) though I prefer to start with 3 and 4 first
Sync 1 with 2 (or 3 with 4)
NOW sync 1&2 with 3&4

3. I want to change what I THINK fitz said (if I'm understanding him the way that he wrote it)

There are ONLY 3 sync screws. One is between carbs 1 and 2; one is between carbs 2 and 3 ( the middle screw); one is between carbs 3 and 4. These are seen looking straight down between them. The fourth big screw is the idle speed screw and that is adjusted from the back of the rack, between carbs 2 and 3, that is NOT the middle sync screw, that's the IDLE speed screw. Yes, it directly affects the 3rd carb, but that's why we adjust the idle as it raises or lowers......by keeping everything balanced to 3. (That's exactly why I prefer to sync 3 with 4 first. keep the idle happy doing that, then adjust 1 with 2 and keep the idle happy, as it was with 3 and 3w/4, then bring 1 and 2 in with 3 and 4 and adjust as needed.)

Adjust the levels between 1 and 2 by turning the vertical screw between carb 1 and 2 (left sync screw). Adjust the levels between carbs 3 and 4 by turning the vertical screw between 3 and 4 (right sync screw). Adjust the balance between the left half and the right half by adjusting the vertical screw between carb 2 and carb 3 (middle sync screw).

As you adjust, it is OK for the idle speed to either climb OR drop. As you hear it doing either, then reach in behind the carbs and adjust the idle speed accordingly (Idle speed screw, yes it's in the middle, but you reach it from behind and sort of below the carb rack) . Make ALL adjustments in small increments and blip the throttle after EACH adjustment and wait for the idle to settle down to it's 'purr' so you can make the next adjustment.

Also, don't lean on the throttle, or the carb rack while working......it is very easy to throw the readings off by doing that.

Last, if you're continuing to get a crazy racing, then you still have a vacuum leak somewhere.....check to make sure the airbox to carb boots and snug on the snorkels of the carbs, and make sure that the carb to head boots are tight. As the bike is running, an unlit but open propane tank briefly aimed and rotated around the boots will tell you if there is a leak or not, but a sudden surge in revs when the propane gets sucked in through the leak.

Keep us posted on what you do, and we'll get you through it. Just ask Moellear what we went through with HIM!!!!! But we got him straightened out.

Fitz, if I am interpreting what you said incorrectly, and you do have it right, I apologize in advance........maybe I'm just reading YOUR post wrong.

Dave Fox

 

Wow, yes! A plethora of information. Lol. Just so everyone knows, yeah I did do the bench sync (albeit wrong i suppose; I only have the idle set screw turned in 2 and 1/2 times). However, I just found it peculiar that after all that time it gets correct and all of a sudden it EXPLODES. I think I am going to try polack's suggestion about tapping the button; it seems that it makes me less nervous to do that. Furthermore, I think my stuffed t-shirts (courtesy of RickCoMatic's post) are drying out inside the FICS tube. The reason I say this is because during the tuning the bike is getting super hot and when I remove the shirts at the end; they are toasted dry. I think that I will try four things tomorrow:
1. Insert more shirts and stuffing into FICS tube
2. Bench sync the carbs so that the idle set screw has a bit more leway
3. try to sync using polack's method of momentary tapping
4. leak propane around my carbs.

I will keep you guys updated to know how this shakes out! I appreciate the help; its awesome to see some of the big names around here pitching in (makes me feel special I suppose!).

 

man you guys are helpful - preparing to sync my bike in a week or so ( when the weather warms up lol ) plan to follow the instructions in the Clymer manual - is anyone aware of anything missing in their instructions ? - have proper sync meter, YICS shut off tool and compression 130 lbs ( give or take 1 or 2 lbs ) at each cylinder - thanking you all in advance

 

I'm still confused about the whole thing with turning the idle screw in/out 2.5 turns, the #3 carb butterfly screw 2.5 times, etc.....

The ONLY thing that I know of that get's an initial 2.5 turn setting is the mixture screws.

As far as I know, for the #3 carb, the butterfly is closed to where a business card or other 'sliver of light' feeler is used for that initial position. None of the other 'flys are clamped down, or anything for that. I leave the screws out far enough so that they don't interfere with setting the #3 'fly first. Once that is set, THEN I adjust the other butterflys to match. Once they match, then the carbs go on the bike. The idle screw is almost all the way out. I start the bike, giving it throttle as needed to get a steady idle WITH the throttle, turning the idle screw in enough til I can release the throttle completely. Once it holds an idle THEN I start the actual syncing, using the Morgan Carbtune. So far, has taken about 5 minutes or so, to do the actual syncing at that point.

FWIW,

dave fox

 

I have a hell of a time doing the carbs sync and only because it was leaking (or sucking) air, just because the boots (carbs joints) where not the correct for this bike...

 

Maybe I'm too new to bikes, XJ's and/or this forum, but what is the "Morgan Tune."

Everyone, thanks for this WEALTH of information. Since buying my first bike, my first XJ AND joining this site ALL less than a month ago, I've learned a LOT. I've got a set of XJ bookmarks categorized for carbs, clutch, general info & maintenance, engine, brakes, you name it!

My carb joints (carb to intake) were dry rotted and crumbling and my bike needs choke to run normally. I've bought a parts bike with good ones and am about to start the process of moving them over tonight, then cleaning the carbs and finding what (if anything) needs rebuilt. Then I get to start tuning. Fortunately, I also saw the posts about checking valve clearances. Since it won't seem to take much time, I'm going to do that, probably while I wait for carb rebuild kits!!! I just have no idea where to get the shims from!!!

Can't wait to get her running again!!!

I'm going to try to film and photograph my efforts at tearing down, cleaning, rebuilding, bench syncing, valve clearance checking, and on-bike tuning (probably with a homemade manometer, unless someone with a 4-gauge sync kit near Columbus, Ohio want to join!) Also, if anyone near me has a colortune... I have beer and an amazing woman who cooks amazing food!!!!!!! (Just to clarify, you get the beer and food ONLY).

-jon