Cv slides rapidly up and down (cb250b4 twin)

[Bert Jan]

Ive got a bike in the shop right now, with a strange problem.
The cv carb slides are rapidly going up and down, like everytime the inlet valve shuts the slide drops. Then when the valve opens the slide does aswell. Bike runs like manure ovviously.

Diagprams are ok. New boots. New o-rings. New seals. Tried the normal things.
Anybody knows whats up with it?

 

[hillsy]

How are the slide springs? Sounds like they might be below spec.

Or the bleed hole at the bottom of the slide is blocked.

 

[Sonreir]

You're running it with the air box off.

Have you checked the health of the diaphragms?

 

[Bert Jan]

How are the slide springs? Sounds like they might be below spec.

Or the bleed hole at the bottom of the slide is blocked.

Not sure how i will be able to check the springs for precision?
Bodies are ultrasonic cleaned, diapgrams are ok, slides are clean.

 

[hillsy]

There should be a free spring length in the workshop manual.

It may not be out of the question that someone has put different (IE: wrong) springs in there....

 

[Bert Jan]

ordered 2 new springs and seal kits. Will report findings. thanks all.

 

[Bert Jan]

One question before the parts come in tomorrow... The slides were doing wonky on idle. CV carb slide does nothing (normally) when bike idles cause mixture goes thru "idle channel".. How can the slide go wonky on idle?

 

[hillsy]

Air is still going past the slides at idle even if the bike is running on the pilot circuit.

 

[Bert Jan]

hmm ok.. i was asuming air went thru the little holes (wich are always blocked by the cheap pods) on idle instead of thru the venturi.