Hi,
This is my 1st post on this forum. Sorry if this has been mentioned before.

I have a 2l zetec running CBR 600 carbs. I have been told that I have connected them wrong. The red and green marked pipes are currently disconnected. If I connect the red one to the cam case breather when I rev the engine the chambers move up and down to expose the butterfly, but the engine then struggles to rev (as if its getting to much air). Disconnected the engine runs but is down on power.

Where should they be connected to? Can anyone help?




[Edited on 15/5/15 by jck239]

Green is the fuel bowl overflow and should be left as it is, the red originally went to a little air filter or the air box, my memory is hazy so should not be blocked or go to the crank breather.

Try moving the needles to get it to run better, I expect someone will be along soon who can advise on jetting, if on a budget get some very small drill bits and drill out what you have.

Regards Mark

Ive got the same set up
Your trumpets are longer than mine - are they stock ones ?
I leave both the red and green pipes off, not needed on car installation
My main jets are 1.8mm and 3 turns out of the idle mixture screw
It goes very well and plugs are a nice colour - 2.5% c/o at mot
You can drill the jets out bit by bit to get the right size ( i bought a modellers set and did 1.6,1.7,1.8)
Then buy new jets in the size that your happy with - theyre weber dgav jets,less than a tenner a set
Every engine is different mind so a session on the rollers would improve things further
But the above is a good starting point
Once its running right it'll be worth it

Thanks.

But what about the things inside the carbs that sit in front of the butterfly and move up and down (sorry i dont know the name of it, i think its some sort of choke). Mine stays closed. If i connect the red pipe to the cam cover breather then when I rev the engine they open as I guess they should.

They are the slides and control the mixture. They move the needle up in the main jet to allow more fuel in. They will move under load without any of the pipes you mention connected up.

Just make sure the carbs are balanced, listening with a bit of tube is surprisingly accurate and when you Rev it all the plungers go up and down in unison, there is a thin rubber memebrane that can become torn in which case 1 will lag behind or even fail to lift.

Another trick for balancing is to use some mig wire or similar as a feeler gauge under each butterfly
Adjust them all so they just touch the wire,then re set the idle once the engine is running
I got them 99% this way

[Edited on 16/5/15 by 19sac65]