help with carb sync

83 xvz12

idle ~1100

#1 balanced at about 4-6 in mercury

#3 balanced at about 18-20 in mercury

idle screw maxed out up

When trying to bring #3/4 down to match #2, can't keep it running, drops idle

Needs #1/2 brought up with idle screw, but already max up-screw limit

Carbs torn apart and cleaned, new gaskets,orings- but missed main fuel needles at the time, recently found it after removing pressed in needle caps, screws were factory? set under caps a mix from 1/2 to 2-1/2 from bottom, reset all a 2 turns

#2 cylinder has less compression than other 3, 150 psi vs 180 psi

also carb#3 leaking small drip from top overfill drain

Suspect I need to pull carbs again due to #3 fuel leak, and re-adjust float,

and clean out needle ports I missed, but not sure that this will let me lower idle screw, while raising #2 vacum?

Open up #2 needle for more fuel?

Disreguard #2 and match other 3 due to lower compression on #2??

Suggestions???

Sounds to me like the butterfly in carb#2 (front left) is being held open by the idle screw, that will reduce vacuum right there. Take the air box off so you can view the throats directly, back out ALL the idle/synch screws. The butterfly valve should be touching both sides of the throat in all 4 carbs and you should have some slack in the outboard throttle cable. Now bring in the idle screw just until the valve starts to open. Then adjust the synch screw for carb 1 (rear left) just until it starts to open. Do the same with 3 & 4. Then reinstall the air box and try doing a synch again. Remember, carb 2 is non-adjustable except for the idle screw. All 3 other carbs are set to this one. The idle will probably be high at this point, bring it back down to 900-1000 before you do the synch. You should see your vacuum increase and be close to the same on all 4. Other than that, it could possibly be a vacuum leak on 1 & 2. Check to make sure they are seated properly in the lower boots and tight.

Good luck and let us know what you find.

Dan

Sounds to me like the butterfly in carb#2 (front left) is being held open

 

Dano, your right. #1and#2 butterflies are open

Backed off idle screw, only 1 turn down greated gap to link(not correct I think)

1 and 2 still open, Backed off all 3 sync screws, 1 and 2 still open

Covered #2 with hand and cranked, created bunch of vacum

3 and 4 closed tightly and appear to be holding 1 and 2 open

Can force 1 and 2 to close a little more with reverse throttle, but will not close tightly

 

Looks like linkage problem, ideas what to look for? :think:Maybe butterflies not centered in bore?

#3 still leaking fuel at overfill and fuel standing on throttle plate

 

Have to run into town, will pull carbs this evening

 

Brian

Sounds to me like the butterfly in carb#2 (front left) is being held open

 

 

Looks like linkage problem, ideas what to look for? :think:Maybe butterflies not centered in bore?

Brian

 

Try adjusting the throttle cables up at the handlebar, sounds like they are too tight (should be a trace of slack in both of the cables) & holding the butterfly open.

 

You will probably have to adjust the idle speed screw afterwards, as needed.

 

 

Try adjusting the throttle cables up at the handlebar, sounds like they are too tight (should be a trace of slack in both of the cables) & holding the butterfly open.

 

disconnected at sliders, didn't help

pulled carbs

with left/right link disconnected, all butterflies close

link about 1/4in too long:think:

 

attached pics, can;t figure how to post here

link is 154mm long, is this correct for 83 xvz12, or do I have a wrong part

considering cutting and rewelding

or is something assembled real wrong?

Make sure that all four carbs are on on axis, that is flat and inline.

A couple of 2x2's under them on hard flat work surface and loosen all the screws on the mount brackets. A couple more 2x2's on the top and clamp them down. When all four carb throats are flat on the surface tighten all the mounting backets screws securely.

That is one way to get them close if you don't have an assmbley plate anyway.

Then check your linkage again. Might be closer. These carbs are extremely picky about being on axis.

One you get them close then while still on the bench adjust each sync screw until each set of butterflys are closed and begin to open at the exact same time.

Cutting and rewelding the link will bring you more problems than you want.

Make sure that all four carbs are on on axis, that is flat and inline.

 

Assembled on 1/4 in steel plate cut to fit between all bracket protrusions. They are flat and do not rock. Did not clamp down, will try it, but don't think this will help.

 

They fit my boots (tightly), but I could try to spread them out Left to Right and see what happens.

 

With all butterflies closed link measures exactly .25in too long.

 

Almost like I have the wrong link?

Make sure that all four carbs are on on axis, that is flat and inline.

 

Assembled on 1/4 in steel plate cut to fit between all bracket protrusions. They are flat and do not rock. Did not clamp down, will try it, but don't think this will help.

 

They fit my boots (tightly), but I could try to spread them out Left to Right and see what happens.

 

With all butterflies closed link measures exactly .25in too long.

 

Almost like I have the wrong link?

 

Ok, reset all brackets while clamping, and wedged carbs as far apart as possible L-R.

Gained a little on the link, but link still too long by width of wall of bushing, .10in.

Can take up this difference with #3 sync screw, but it takes all of it screwed all the way in with counter spring completely compressed. (this would be alright only if I need to loosen #3 sync screw during sync test)

 

Any more ideas? Could try to Z-bend link a little bit?

There's something bent in the Linkage. Usually, it's on the left Side because it sticks out from underneath. Could it be possible, you clamped the Carbs down while mounting first without a cutout to take up the Lever ?

There's something bent in the Linkage. Usually, it's on the left Side because it sticks out from underneath. Could it be possible, you clamped the Carbs down while mounting first without a cutout to take up the Lever ?

??

Unless something is assembled very wrong, the only things thay are below the level of the bottom throats when on a flat plate are the bottom mount rails with drain tubes and idle screw.

No linkage is this low, unless something is wrong

Someone have pics handy of proper linkage setup?

Sorry, no Picture, but i can ensure you, the Linkage gotta be sticking out a bit, maybe 4 mm or so on the left Side. I made up a Jig for this a long Time ago, so i i can't say for sure how much it's sticking out above the Level of all Carb Foots. The Mount Rails which take the Drain Hoses are even lower than that, but my Jig is smaller than the Distance between the Rails.

Heres pics of this pain in the _ _ _ _

Anyone see the problem

2 pics left carbs link too long and ruler across throat, lots of clearance

1 pics right carbs clearance-close

2 pics right carbs sync screw, to long, and adjusted for link to fit

1 pic left link fits with with right sync screw all the way in

all pics with butterflies properly closed

can cams be rotated on butterfly shafts?

Well, those Pics aren't too sharp in the depth, but from how i see it, it looks like the Linkage Parts are on the wrong Carbs. Did you have them completely apart and exchanged Linkages between front and rear left Carb ?

I honestly don't know if thats possible, some of these a pressed on, some have thin Nuts on the Butterfly Valve Axle.

I don't work on the Carbs every Day anymore, so i could be all wrong, but that's the Way i see it.

Well, those Pics aren't too sharp in the depth, but from how i see it, it looks like the Linkage Parts are on the wrong Carbs. Did you have them completely apart and exchanged Linkages between front and rear left Carb ?

 

I honestly don't know if thats possible, some of these a pressed on, some have thin Nuts on the Butterfly Valve Axle.

 

I don't work on the Carbs every Day anymore, so i could be all wrong, but that's the Way i see it.

Can I take some specific pics to determine if linkage is correct?

Yes, I seperated carbs, but they are back together the way they were when I got this bike. did not pull butterfly shafts/cams.

I have a disassembled Carb Set lying in the Shop, i could take Pics of these and put them up here. But i won't get to the Shop until tomorrow, or better said 18 Hours from now on.

If there's no one else chiming in, we'll have to postpone until then ...

After much discussion, and studying over and over again of my setup, I finally realized that the L-shape link that the #3 sync screw pushes against was bent/angled. Upon straightening, long link fit at about 1/2 depth of the #3 sync screw.

Thank you all for your assistance, would not have figured it out without your help.

Now I just have to put the rest of this beast back together

Again Thanx

Brian

:big-grin-emoticon:

After much discussion, and studying over and over again of my setup, I finally realized that the L-shape link that the #3 sync screw pushes against was bent/angled. Upon straightening, long link fit at about 1/2 depth of the #3 sync screw.

 

Thank you all for your assistance, would not have figured it out without your help.

 

Now I just have to put the rest of this beast back together

 

Again Thanx

Brian

 

:big-grin-emoticon:

Yup, lots to put back together.

Good time to check / lube the throttle & choke cables, during assembly (if not already done).