Not enough vaccum on #2 carb??

[dlopes]

I'm trying to sync my carbs and I'm having problems with the #2 carb. I am using a Carbtune 2 and I can't get enough vaccum to move the #2 rod up at all. I swapped the #1 and #2 tubes and the guage works fine. I messed around with the pilot screw as well as the #1/#2 sync adj screw. When I blip the throttle, it does move up a little, but goes back down. WTF now???:bang head:

 

[maleko89]

The #2 or left-front carb is fixed and the sync screws have no affect. Try raising the idle using left side thumb screw.

 

[dlopes]

Tried the thumb screw, no help. When it is running, I hear a noise similar to someone puffing or sucking air through a straw coming from the #2 carb. Is this normal? This is my first VMAX and when I bought it, it was running really rough so I rebuilt the carbs. What could be wrong with the #2 carb? :damn angry:

 

[maxcruiser]

Tried the thumb screw, no help. When it is running, I hear a noise similar to someone puffing or sucking air through a straw coming from the #2 carb. Is this normal? This is my first VMAX and when I bought it, it was running really rough so I rebuilt the carbs. What could be wrong with the #2 carb? :damn angry:

Is the sparkplug tight? If so, I would check compression on all the cylinders, especially on #2.

Mike

 

[maleko89]

That noise could be a vacuum leak or the choke plunger isn't all the way closed for that carb.

 

[dlopes]

I found out why I'm loosing vacuum and where that straw sucking noise is coming from. The #2 carb's butterfly is not closing all the way. It's not the throttle cable either. It's like this on the bench. I have the thumb screw all the way out and it still has a constant gap. Is this normal? If not, what could be wrong?

 

[maleko89]

That's normal. #2 carb is fixed and will only close so far. The other butterflies should be open a bit too. The bike won't idle on the pilot circuit alone. It needs a bit of air going through the main bore.

 

[dlopes]

Well, I took off the carbs and replaced the choke plunger. Still no help. Any suggestions on what to look at?

 

[maleko89]

Spray some water around the boots and see if the engine tone changes. Make sure manifold isn't leaking.

 

[dlopes]

Tried the water....no change. I have a compression tester, but I don't have the right fitting for the plug size. Just wondering, can an exhaust leak or a valve cover leak cause a loss of vacuum? Do I have to open my vboost butterfly's during sync at all? I'm keeping them fully closed right now. I'm not sure what else to try. It's starting to look like I bought a lemon. uke::angry flame::shot::th_signs60:ullhair:

 

[tfisher65]

If you're going to check for vacuum leaks around the boots, spray with starter fluid or WD40. I wouldn't recommend water.

 

[maleko89]

Are you sure the choke plunger is all the way closed? You said you replaced the choke but is the linkage and fork allowing the plunger to be pushed all the way in? Is the rib on the bottom of the carb even with the boot? Clamps are tight? Is the manifold tight? Any cracks near the side cover mounting hole? What happens if you cover the top of that velocity stack? Does it go up then?

 

[maleko89]

One more thing to check is your throttle cables.

 

[dlopes]

Throttle cables are good. All clamps are tight. The manifold is tight with a new o ring. Choke plunger is completely closed. Carb is even with the boot. No cracks are visible. I covered up the top of the carb and it cuts off with no rise in the meter. Could there be anything wrong with the carb internally? Could the #2 cylinder rings be bad? What about the exhaust? Could an exhaust leak lead to loss of vacuum? I'm thinking about surrendering to my local Yamaha rip off artist. :confused2: