carbs problem? with velocity stacks

[Frojku]

Hi, today I just put velocity stacks to my carbs. I also put 140 main jets, 2,5 turn mixture screw. The problem is - when I run faster with wide open throttle, engine sounds like it has no power, fuel and slowly shut down that I need to run engine again. Should I put bigger main jets? Maybe 150? Or stock 132.5? Or do something with mixture screw?

Sorry for my bad English : )

 

[grizld1]

Slides in your carburetors are lifted by the difference between low air pressure above the diaphragm and atmospheric pressure below. Air currents moving across the lower diaphragm chamber vent can cause low pressure below the diaphragm. This is why vacuum carburetors perform best with a still air box, acceptably with large volume pod filters, badly with small volume pod filters, and very badly indeed with stacks.

 

[Frojku]

Yes, but I would give them a chance. I heard that sometimes they run good. Is there any hope?

 

[Hitndahedfred]

I tried stacks on my bike,,, gave up trying to get it ro run the way I wanted,, And I did many jet changes.
Now I am running a K&N conical pod.
Runs great.
Besides you will need to run screens/foam on the stacks anyway to keep errant airborne things from getting sucked in.
So even they are cool looking,,, I would go with Griz's recommendation. Since you did not specify which carb you were running.
I am using a single VM34.

 

[Frojku]

Unfortunately I am using BS34...

 

[gggGary]

i think "no hope" is a a good call for that set up.
Welcome to the forum! We need to see pics!

 

[grizld1]

Fred, the OP is using OE vacuum slide carburetors (he didn't say so originally, but his jets did). The pod you're using is fine on an aftermarket mechanical slide VM34, but it will make a kinghell mess on any vacuum carburetor.

 

[grizld1]

One of these days I'm going to try to get the image on the Yamaha 650 Society T-shirts changed. It shows a motor with BS38's and stacks, and it publicizes one of the worst mistakes you can make.

 

[retiredgentleman]

Yeah, most lads care more about the "look" of their engine than how well it runs.

 

[Frojku]

I care both on how it runs and how it looks, so thats why I'm asking for a help . I will try with another jets, if it won't work, I will get back to uni pods.
Gary later I will post pics for sure!

 

[XSLeo]

The Uni Filters are the best pods to use.
Leo