I need help figuring out carb sync issues

[thebottle]

I'm having problems syncing the carbs... I'm using a vacuum gauge and right now I have carbs 1,3,4 all the same, but I can't get carb 2 in line... carb 2 is much, much higher than the rest of them. Also, I noticed that the vacuum advance is making noise, sort of sounds like it's rattling back and forth for some reason... and that's connected to that carb, so could it be something with that?

Here's the thing, it runs great! I can do the 5th gear roll on. I have no power loss all the way up, low-mid-high... except for one thing, when I let off the throttle and come to a stop, it takes longer for it to come all the way back down, and sometimes even hangs at 1,500 for a while before dropping back into the normal idle, which I have set to about 1,000. What the hell is going on? I'm at a loss, and any advice would be greatly appreciated, thanks!

[DAVINCI]

What have you done to the carbs lately?

[Schming]

Is your vacuum advance hose hooked to #2 carb or the intake manifold ?

[MindWebs]

Wi...

check the engine side intake boots with propane or carb cleaner..

with the bike running, spray carb cleaner around intake's to see if you have a leak. if the RPM's increase then you've got leaks..

what town are you by? i may be able to lend a hand.

i'm 20 minute west of menonmonie

50 minutes west of eau claire

are you using harbor freght gauges?
they work ok, but can "lose" calibration.

this the bike running and the throttle locked, switch gauges between carbs and see if the numbers read the same between gauges per cylinder.

alway's remember to keep a fan going on the motor while running, and don't run it too long. overheating will take out the rings.(among other things)

let me know, PM or whatever works.

[motoman]

If vacuum advance can is rattling at idle, U have the vacuum hose plugged on #2 intake boot instead of #2 carb which is ported vacuum and has a built-in restricter at base of brass tube.(no vacuum at idle).

From left to right, first screw sync's #2 to #1. Third screw sync's #4 to #3. Second screw sync's pairs together. #3 is 'master' carb.
Still being out of sync attributes to the 'hang-idle' and idle mixes are likely on the lean side. Changing idle mixes changes sync......they go hand-in-hand.

[thebottle]

What have you done to the carbs lately?

I rebuilt them last year. And this year cleaned them again, and checked all the float heights.

Is your vacuum advance hose hooked to #2 carb or the intake manifold ?

It is hooked to the #2 carb body, not the intake boot.

From left to right, first screw sync's #2 to #1. Third screw sync's #4 to #3. Second screw sync's pairs together. #3 is 'master' carb.

Is that right? I thought, the first screw adjusts #1 carb, the middle screw adjusts #2 carb, the third screw adjusts #4 carb, and #3 can only be adjusted with the main idle screw, which also changes all 4 carbs together... at least when I had the carbs out and I was adjusting them to be close, that's how it seemed to work for me.

with the bike running, spray carb cleaner around intake's to see if you have a leak. if the RPM's increase then you've got leaks..

They are new boots, last year. But I will check for this tomorrow.

this the bike running and the throttle locked, switch gauges between carbs and see if the numbers read the same between gauges per cylinder

I'll have to wait until tomorrow to check on this too.

what town are you by? i may be able to lend a hand.

Neenah, I'm pretty far away, .

Still being out of sync attributes to the 'hang-idle' and idle mixes are likely on the lean side. Changing idle mixes changes sync......they go hand-in-hand.

I have not tried adjusting my mixes yet... I wanted to get the carbs synced first... but 1,4 are tan/white like they are supposed to be, but 2,3 are on the black side so I definitely need to adjust those.

[Ken Talbot]

...
Is that right? I thought, the first screw adjusts #1 carb, the middle screw adjusts #2 carb, the third screw adjusts #4 carb, and #3 can only be adjusted with the main idle screw, which also changes all 4 carbs together....

The screw between carb#1 and #2 sets butterflies #1 and #2 relative to each other. The same happens with the screw between carb #3 and #4 - it adjusts butterflies #3 and #4 relative to each other. The screw between carb #2 and #3 adjusts the left pair relative to the right pair. The screw that changes all four together is the idle speed ajustment screw.

[thebottle]

The screw between carb#1 and #2 sets butterflies #1 and #2 relative to each other. The same happens with the screw between carb #3 and #4 - it adjusts butterflies #3 and #4 relative to each other. The screw between carb #2 and #3 adjusts the left pair relative to the right pair. The screw that changes all four together is the idle speed ajustment screw.

Are you sure? Even this says it is the way that I stated:

http://www.xs11.com/xs11-info/tech-tips/maintenance/carburators/71-pre-synchronizing-carburetors.html

I don't understand how they could adjust relative to each other anyway? When I had them out... I know it worked like the article that I linked, with the first screw opening/closing #1 butterfly, middle screw #2, third screw #4. And when they were out I set them by taking the idle all the way down so #3 was closed, filling it with carb cleaner, slowly opening it until the cleaner drained back into the bowl. Then closing the other 3 butterflies with their respective screws and doing the same. I did that instead of poking a wire through the butterflies, and it worked pretty good for me.

[mikubuilder]

Well ,you kinda answered your own question, that is that your advance hose is connected to wrong nipple. It should be on carb holder ,not on carb body ,that nipple is for vacuum to petcock....that's probably why your vac advance makes that noise. ..

[mikubuilder]

Also, when you bench sync your carbs you can see how adjustments are made to the butterflies, it's easier to understand relationship between them.

[crazy steve]

Well ,you kinda answered your own question, that is that your advance hose is connected to wrong nipple. It should be on carb holder ,not on carb body ,that nipple is for vacuum to petcock....that's probably why your vac advance makes that noise. ..

Nope, the advance goes to the carb body, not the manifold. And Ken is giving you the straight scoop on adjusting them. Keep in mind that you'll have to adjust and readjust as you go though them, as changing one will effect the others some but as you go through them the differences will keep getting smaller until they're gone...

[Schming]

^^^^Confirmed^^^^

[mikubuilder]

I stand corrected. ...haven't seen my scoot in about 4 months
Damn winter. ...

[MindWebs]

Sweet..

i love it when it's something that's easy..

your lucky bottle..

some times things can get intresting on these old 11's

yeah, neenah is a little bit of a drive, 225 miles

if it was riding weather that would be a nice drive, i was there a couple years ago. some years i make it to the iola car show/swap meet, your just a bit past that.

so, carb 2 (from left to right as you sit on bike) is the "constant" 1,3,4 get adjusted to match #2

happy tuning

also, keep an eye out in the rallies for the "lost" rallie it's a good time.
great food, great people, lots of fun..

[thebottle]

I got it synced today! Woot! The problem was that I didn't realize that changing one changed the others... but after reading a couple of the comments on here saw just that and was able to get them all in line with each other. Thanks a bunch!