Webbers Spitting

[ian.hoper]

Hi Each

Numty question , My X Flow on DCOE 40s runns ok save for cruising in traffic say between 3rd or 4th spits back seemingly via missab joint on progression( presume its that ) . Have to keep changing down and accelerating to avoid it doing this .

Have a new ball shaped carb flow meter and it registers 5 on three ports save for a dip to 4 on one port ,

Think you all will say its running too lean on one but how do you increase the fuel to stop it happening . Have tried the idle jets route.

Only seems to hapopen at a certain throttle position ,lift off mostly following traffic.

Any guide appreciated . Goes ok when foot down ?

[eric]

you must have 5 on the 4 ports

or 4 on the 4 ports

 

use the screw adjustement under the white cap

 

[Paul McKenzie]

just richen the weak choke

[eric]

I have experienced this problem

 

main causes are :

unbalanced webers

weak richness open screw

and tank not open to air (use a special item which let the air enter but not the petrol go out)

 

It is now very rare but sometimes still hapen

[ian.hoper]

Hi Eric and Paul

Thanks for that but Eric my carbs are old style and no white cap but have the Webber manual so will look see .

Best blatting .

[eric]

if there are old style, you cannot adjust the flow by the by-pass you haven't

so I understand that on the same carb there 5 on one port and 4 on the other

Test the compression of the Cylinder of the 4 level compare to the other

if it is same as the other, check for air leak on the manifold or between the weber and the manifold

if all is ok, the weber have not the level of aperture on each port

and there you need a specialist

You can simply check with another weber

[millsn]

Carbs on an XF do spit back at certain rpm, the thwacker thwacker sound is the air not making up its mind which dirfection to go in at certain revs (around 3-4K if I recall). AS far as I know there's little you can do about it

[eric]

Increase the iddle jets, to 60F8 will solve the problem but may cause some others as

poor running in traffic jam or under 3000 revs

So better is to use 50F9 with a opened setting ( 1/4 rev out after the right setting)

 

Balance the carbs is really important because spitting back is a sign of an unbalanced carb, it means that same ports of a same carbs must be balanced !!!!

 

Free air flow in the tank is also important

I just set a no return valve which let the air coming in but not the petyrol going out

 

If it can help

 

you can write me directly at eric@bonzai.fr

 

 

[ian.hoper]

Hi Eric

That's very helpfull ,have spent a lot of money trying to get it running right and this may be the answer .Avoided the rolling road avenue ( excuse the pun ) as last time i went that route it only lasted a few 100 miles before problems on running surfaced again so want to sort it myself by hook or by crook and learn a bit more about Webbers /ignition etc .

Before I had the Lead free head done it used to run like a sewing machine ?

May have to install the spare x/flow engine this winter and see if that makes a big difference .

Will be in touch .

Best wishes